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    Introduction

    When doing electrical work there is a real risk of the power accidentally being left on before starting work. Dropping concentration for a few seconds is enough to cause death. Over the weekend I helped a friend repair his hot water boiler, and despite knowing that the power had been switched off, and verifying with a meter, I still felt uncomfortable enough to avoid touching any wiring unless absolutely needed. A fuse of perhaps 5A was fitted, and it would not have helped protect us in the event that the wiring was accidentally still live. It is easy to make a mistake and switch off the incorrect circuit breaker. The dangers are multiplied further in an industrial environment where there is a lot more live wiring, often three phases, and far higher current consumption.

     

    What we call a small ‘consumer unit’ or fuseboard in homes in the UK (nowadays there would be circuit breakers and residual current devices (RCD) fitted) is replaced with large cabinets in labs and factories. Wiring the size of pipes is plumbed into the buildings, requiring digging huge trenches. Everything is on a huge scale.

     

    According to the US National Fire Protection Association (NFPA) Standard for Electrical Safety in the Workplace (NFPA 70E), establishing a safe work environment involves testing for absence of voltage, and this requires that whatever test equipment you use (voltage tester, multimeter and so on) is verified against a known voltage source both before and after the absence of voltage test is performed. The procedure is quite involved; each phase must be verified, phase-to-phase, and phase-to-ground. Before and after each test, the test equipment must be verified to be functioning against a known voltage source. That’s a lot of test steps!

     

    The Panduit ‘VeriSafe’ absence of voltage tester is designed to do all that; it automates the verification procedure, saving the user from having to manually perform these steps, saving time, money and reducing the risk of error. It is basically a device that is permanently wired into the enclosure or controlled area, and it becomes very convenient to do all the tests using a single button-press.

     

    Although the NFPA 70E standard is for the US, there could be applicability for the VeriSafe tester in other countries with similar requirements.

     

    I was keen to explore this unusual but potentially life-saving product. Here in the UK, I do have some experience with Panduit products, in particular their 19-inch racks. They are known for high quality.

     

    This short (5-minute) video provides a quick overview and demo of the VeriSafe solution:

     

     

    An Example Lab

    One of the labs that I explored contained power distribution units (PDUs) with an emergency cut-off button, and indicator lights for each phase:

     

    These PDUs are used to distribute power to aisles of electrical equipment in labs and factories. In this example, a server room is being powered:

     

    Sometimes it is achieved with under-floor cabling; here cable trays at ceiling level are used:

     

    There are connectors to feed the power all along the aisle:

     

    The power requirement to run the server equipment and to cool it all is fairly high! The risks are severe for any engineer who doesn’t ensure a safe work environment when working inside the power cabinets.

     

    What's in the Box?

    The VeriSafe solution arrived in a very large box, dwarfing my lunch:

     

    However, there was a lot in the box – predominantly the cables. The coloured wires are used to connect to all of the phases of power inside the cabinet and to the earth too. Each connection is a pair of wires, i.e. doubled-up for providing a reliable test that can even identify if a cable has become disconnected. The system checks for continuity between the two wires in the pairs basically.

     

    It was great to see a very comprehensive 18 page user manual (entirely in English, although the safety warning information page is also in French) inside the box. It is in full colour, with detailed diagrams showing how to perform connections for different wiring systems (three phase delta, wye, single phase and different earthing systems that may be encountered). A set of round stickers is also supplied that are only needed if the VeriSafe product is being installed with different language requirement, and a yellow set of stickers in multiple languages, that has a brief test procedure which can be stuck in a visible location. A nice touch is the QR code on there, for getting all the detailed product information immediately using a mobile phone. Note that it is wise to do this and only use the paper manual as a guideline. The latest VeriSafe online user manual (PDF) should always be used to install this VeriSafe product.

     

    The VeriSafe system consists of two key parts; the large isolation module with the multi-colored wires, and a yellow indicator module. The isolation module is wired up to all the phases and to the earth, and then there is a single interconnect cable (with RJ45 style connectors) that joins it to the indicator module that is mounted in a user accessible location. The system is Category 3 (600V) rated.

     

    The supplied black 60cm interconnect cable is called the ‘System Cable’ in VeriSafe terminology. Although it looks like it could be replaced with any RJ45 network cable, I believe it is incompatible, and the right-angle part is quite unusual, it fits very deeply inside the indicator module (there is a clip on the indicator module that needs to be partially pulled upward (forcefully) if the cable ever needs removing; it won’t accidentally fall out with vibration).

     

    A supplied 3.6V AA sized lithium battery fits inside the indicator module. There are actually a couple of rubber seals (and a small amount of silicone grease), so it is unlikely that dust will get inside this module in ordinary use, and it is approved for wash-down (IP66). The type of plastic wasn’t marked, but it feels very tough.

     

    An electrical installer would not need any unusual or additional tool to deploy VeriSafe, apart from perhaps a drill and a punch for a 30mm hole and a 2mm notch. Apparently, this is a standard sized knockout, so no tool may be needed to make the hole. A depth of 90mm is needed behind the knockout for the indicator module. The wires from the isolation module have no supplied connectors, and the wires would be attached to each phase using existing approved connection methods. The user manual goes into the detail of precautions to take and how to route the wires. The isolation module can either snap onto a standard rail (DIN rail) or can be screwed to a surface using three screw holes (screws not supplied; #8, or M4 is the ideal fit for the holes).

     

    The indicator module has a simple interface, with just one button to press to start the test. When the wiring is normally live, there will be three lights glowing red to indicate that dangerous voltages are present. When the test is running, a central triangle flashes and then pauses for a few seconds, and then flashes out a code if the environment is not safe to work on. The code tells you (by the number of flashes) if the wiring is live or there is some cable fault.

     

    On the other hand, if the environment is safely powered down, then a green outer partial ring glows. That is the only scenario where you can be confident that there is no power, and the environment is safe (engineers should still take precautions however – one can’t predict if someone else will override the power cut-off for example, while you are working. Sensible engineers will place warnings at a minimum, and follow their procedures for ensuring no-one else can switch the power on inadvertently).

     

    A nice feature is that the isolation module has four screw terminals that are for two relay contacts that close whenever the system is indicating green. This allows for redundancy by wiring the contacts in series, and the connections can go to a logging system or an industrial IoT system for reporting.

     

    Three-Phase Supply Tests

    To test the system, I didn’t use a real three phase supply – most individuals do not have access to this, and I wanted to test it in a safe environment before subjecting it to a real mains test.  So, I used a low voltage three phase system. Instead of 208/380/415V RMS (depending on what country you're in), it offers around 6V RMS phase-to-phase! Super-safe, ideal for simulating the power into a factory. Another cool way is to use a variable frequency drive and three step-down transformers.

     

    Each of the three phases from the test 3-phase supply were connected to pairs of wires attached to the isolation module. My three-phase test supply has a neutral connection, which I treated as the earth connection. So, all eight wires (two for each phase, and two for earth) from the isolation module were connected to the three-phase test supply.

     

    Next I proceeded to run some tests including single points of failure such as a disconnection of one of the wires in a pair from the isolation module. The VeriSafe system behaved as expected. Note that multiple failures are not guaranteed to provide correct indication; for an example, see Peter's RoadTest Review where he identifies and details a scenario where a broken wire falls on a metal chassis connected to earth. There are specific rules on installation that must be followed to prevent a double failure (e.g. using wire ties to prevent a loose wire from falling where it shouldn’t). For situations where more than one fault must not be tolerated, I wouldn’t rule out the idea to install two VeriSafe units, and have a procedure where both units must provide a green signal and both units are to have their relay contacts wired in series to a management platform.

     

    Single Phase Mains Supply Tests

    With some practice gained in using the VeriSafe product with the safe three-phase supply, I proceeded to hook it up to the single phase real mains supply at home.

     

    Here the live and neutral wires are connected to pairs of wires from the isolation module, and the third phase pair and the earth pair are wired together (this is detailed in the VeriSafe user manual). With the mains power switched off, I got the green light as expected.

     

    Next, I switched on the mains supply, and the red hazardous voltage indicators came on, again as expected. Pressing the test button caused the triangle to flash a code indicating that voltage was present.

     

    Reliability

    I was curious, how reliable is the unit, if it is permanently connected in electrical cabinets? The VeriSafe product is designed to achieve a Safety Integrity Level of SIL3, which for this continuous operation product means a probability of failure per hour to be in the range 10-7 to 10-8. In other words, if you had a hundred of these devices deployed, then you could expect to perhaps have to replace one in ten years of continuous operation. Note: I am not a probability or a reliability expert, so please do run the sums if you need to, and let me know in the comments below.

     

    In contrast a multimeter is not permanently energised; it is only energised for the length of the tests. However, such a direct comparison is meaningless; an engineer will still use a multimeter and other test tools where needed, and furthermore the risk of not performing the test procedure correctly in ten years is far higher when there are many manual steps to perform, so I’m convinced that the VeriSafe product serves a valuable purpose.

     

    Digging further into the safety aspects, the VeriSafe product is designed to meet immunity requirements for safety related systems  based on IEC standards, and meets software requirements for safety related systems too, to IEC standards (the full set is listed in the technical specifications section in the VeriSafe PDF user manual). In terms of electrical requirements, there is no need to have an inline fuse when wiring the isolation module. It is tested to withstand transients of up to 6kV.

     

    I was keen to see the internal build quality; there are four screws that hold the IP20 rated isolation module together.

     

    The top board performs the majority of the isolation task. The other side of that board contains some physically large disc capacitors, which I believe are Vishay, rated X1 and Y1, designed for permanent connections.

     

    The other board contains the processing circuitry. The connections between the boards are with 0.1 inch header pins and sockets, i.e. a board interconnect technique known for reliability (the same techniques are even seen in military equipment).

     

    Summary

    I love that Panduit thought out-of-the-box to made things safer for engineers in a high risk environment. I was very surprised at the level of sophistication for the VeriSafe Absence of Voltage tester. It is straightforward to install (but read all the instructions, and get familiar with it!) and extremely easy to use, I liked that there is no ambiguity with the indications, a green light is mandatory to determine that the environment is safe to work in (as mentioned, it is wise to still take precautions), and that it collapses multiple manual test steps into a single button-press, eliminating user error in most cases.

     

    The internals look well constructed too, and there should be an easy return-on-investment exercise for engineers who know how long it takes them to run manual absence of voltage tests. The risk of making a mistake is of course dramatically reduced, and that should be a huge motivator to evaluate VeriSafe and decide if it is worthwhile to deploy it.


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    Hi there,

     

    I've got the TENMA  72-1040572-10405 and I was wondering if a transistor hfe measurement is possible The manual is not helping here however the display during power on is showing a hfe entry which is also mentioned in the manual(display symbols 9 hfe Transistor testing indicator It discribes in the manual"The meter can measure AC7DC voltage and Current Resistance Diode Continuity Buzzer Capacitance Frequency temperature(C or F hFE amd EF Function without going further into detail Also the multi purpose socket is prepared to take NPN or PNP transistors but I have no clue how to get started Any help

     

    Thanks!


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    The Hack Like Heck Competition

    Do you like creating things with electronics?

    Do you like to make videos of the action?

    Are you the next Ben Heck?

    We want you!!

    About Hack Like Heck
    Content Partner Program
    The Prizes

     

    Here's what we're giving the top ten audition winners. . .

     

    Parts from:

    Buy Kit*Buy Kit*

    Product Name Manufacturer Part Number
    Quantity
    Part Link
    Raspberry Pi Model A, BCM2835 RASPBRRY-MODA+-512M 1 Buy NowBuy Now
    PCB, No Holes, Single Clad 12X12WEC112X12WEC1 1 Buy NowBuy Now
    Display Panel, Capacitive Touchscreen, TFT, 480 x 272 RK043FN02H-CT 1 Buy NowBuy Now
    EVQ-Q2W03WEVQ-Q2W03WTactile Switch
    EVQ-Q2W03WEVQ-Q2W03W 16 Buy NowBuy Now
    Micro SD Card, 16 GB
    TSRASPI10-16GTSRASPI10-16G 1 Buy NowBuy Now
    SMD Chip Resistor, 33 ohm MC0805S8F330JT5EMC0805S8F330JT5E 21 Buy NowBuy Now
    USB Hub, Bus Powered, USB 3.0, 4 Ports U3-4HUB 1 Buy NowBuy Now
    Ribbon Cable, 40 Conductor, 30 AWG (cut to 10") HF447/40 100' 1 Buy NowBuy Now
    Ribbon Cable, 50 Conductor, 28 AWG (cut to 10") R2651DTSY50SC85 1 Buy NowBuy Now
    Speaker, Buzzer, Piezo, 8 ohm, 83 dB, 0 Hz to 3 kHz MCKP2644SP1F-4748MCKP2644SP1F-4748 2 Buy NowBuy Now


    Parts From:

    Product Name Manufacturer Part Number
    Quantity
    Adafruit-40-pin-TFT-Friend 1932 1
    Adafruit-MAX98306-Class-D-Amp 987 1
    Adafruit-PowerBoost-1000C-master
    2465 1
    Lithium Ion Polymer Battery - 3.7v 2500mAh
    328 1

     

    Get the Full Bom, Datasheets, Design Files, and Schematics on Github


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  • 02/17/18--02:13: Which OS For Development
  • Recently my Windows10 OS has started to crash randomly and each time I spend quite a while waiting for it to reset and then more time trying to solve the issue. So far I haven't managed to find the cause and fix it. My system spec is AMD Phenom II x4 840, 4GB RAM, basic graphics card.

     

    This has led me to consider switching to another OS and I am wondering what other developers use at home for electronics and making; Eagle PCB layout, 3D printing, Microchip MPLAB X , OpenSCAD, Wireshark, Android Studio, etc (all the good stuff we see on Element14).

     

    Therefore my poll question is:

    What OS do you use at home for building, programming and testing projects?

     

    Please feel free to use the comments section to add any detail; good or bad.

    [My apologies to OS development teams if you've been left off my poll list. ]

     

    I look forward to seeing the results, thank you.


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    {tabbedtable} Tab Label Tab Content
    About

    The Arty S7 board features new Xilinx Spartan-7 FPGA and is the latest member of the Arty family for Makers and Hobbyists.

     

    The Spartan-7 FPGA offers the most size, performance, and cost-conscious design engineered with the latest technologies from Xilinx and is fully compatible with Vivado Design Suite. Putting this FPGA in the Arty form factor provides users with a wide variety of I/O and expansion options.

     

    Use the dual row Arduino® connectors to mount one of the hundreds of hardware compatible shields available, or use the Pmod ports with Digilent's pre-made Pmod IP blocks for a more streamlined design experience. Arty S7 was designed to be MicroBlaze ready and comes out of the box ready to use with Xilinx's WebPACK licensing.

     

    Features

    • Xilinx Spartan-7 50 FPGA (xc7s50csga324-1)
    • 8,150 slices (each slice contains four 6-input LUTs and 8 flip-flops)
    • 2,700 Kbits of fast block RAM
    • Five clock management tiles, each with a phase-locked loop (PLL)
    • 120 DSP slices
    • Internal clock speeds exceeding 450MHz
    • On-chip analog-to-digital converter (XADC)
    • Programmable over JTAG and Quad-SPI Flash

     

    Memory

    • 256MB DDR3L with a 16-bit bus @ 650MHz
    • 16MB Quad-SPI Flash

     

    Power

    • Powered from USB or any 7V-15V external power source

     

    USB

    • USB-JTAG Programming circuitry
    • USB-UART Bridge

     

    Switches, Push-buttons, and LEDs

    • 4 Switches
    • 4 Buttons
    • 1 Reset Button
    • 4 LEDs
    • 2 RGB LEDs

     

    Expansion Connectors

    4 Pmod ports

    • 32 total FPGA I/O (16 shared with shield connector)

     

    Arduino/chipKIT Shield connector

    • 45 total FPGA I/O (16 shared with Pmod connectors)
    • 6 Single-ended 0-3.3V Analog inputs to XADC
    • 3 Differential 0-1.0V Analog input pairs to XADC
    RoadTesters

    The following applicants were selected as official roadtesters:

     

    dixon415

    14rhb

    dhmarinov

    gecoz

    asher.bsher

    Terms and Conditions

    Digilent ARTY S7 Dev Board (Xilinx Spartan 7)– RoadTest

    Terms and Conditions

    These are the terms and conditions which govern the Digilent ARTY S7 Dev Board (Xilinx Spartan 7)RoadTest contest. This Contest requires participants to submit an application indicating their previous experience with this type of equipment/component, information on what they would do to test the equipment/component, and the applicant’s desire to post a thorough review of their experience with images, photos, or other supplemental materials. Participants will be required to meet the Conditions for Participation.  The winners of this RoadTest will receive the item(s) listed below. RoadTest Reviews are due no later than 60 days after the receipt of the item(s). No other prizes are offered.

    The Principal terms of the Competition:

    The following words and phrases are used in these terms and conditions and have the meanings given to them below.

    Digilent ARTY S7 Dev Board (Xilinx Spartan 7)

    (RoadTest or Contest)

    Key dates:

    Applications Close: midnight (GMT) on Feb 12 2018

    Announcement of Winner (estimated): Feb 19 2018

     

    Prize: Digilent ARTY S7 Dev Board (Xilinx Spartan 7)

    Additional Prizes: none

    Competition Site: https://www.element14.com/community/groups/roadtest?ICID=menubar_resources_roadtest

    Site or element14 Community: www.element14.com/community

    Judges: members of the element14 community team chosen at the Organiser’s discretion.

    Judging Criteria, All of the following which will have equal weighting:

    · Demonstrated competence with the technologies including links or descriptions of past projects

    · Qualifications as indicated by current job role and/or schooling/vocational training;

    · A thorough description of how the prize would be tested;

    · Likelihood that the Applicant will blog about the prize and provide a review on element14.com;

    · Originality;

    · Innovation.

    Organiser: Premier Farnell plc (registered in England and Wales under company number 876412) whose registered office is at Farnell House, Forge Lane, Leeds, UK

    Conditions for Qualification: in addition to meeting the requirements of these terms, all persons applying to take part in the Contest (each one an Applicant) must:

    · Provide a RoadTest application describing what he/she would do if awarded the Prize including similar previous projects, product experience and qualifications

    Terms: these terms and conditions which govern the Competition and to which the Organiser reserves the right to make changes from time to time and the latest version of these Terms from time to time will be posted to the Site.

    1. Eligibility
    2. Applications:
    3. Selecting Winners: 
    4. Liability:
    5. General:

    1.1 Save as set out in these Terms, the Contest is open to any natural or legal person, firm or company or group of natural persons or unincorporated body.

    1.2 All Applicants must be aged at least 18 at the time of their application.

    1.3 Applicants must not enter the RoadTest if doing so or taking part may:

    1.3.1 cause the Organiser and/or themselves to be in breach of any agreement (including but not limited to any contract of employment) to which they are a party or in breach of any law, regulation or rule having the force of law to which the Organiser or the Applicant may be subject or any policy of the Organiser or the Sponsor;

    1.3.2 Require the Organiser to obtain any licence, authorisation or permission to deal with the Applicant; or

    1.3.3 Be in breach of any policy or practice of their employer. Some employers prohibit or restrict their employees from taking part in competitions such as these or receiving prizes under them and the Organiser respects those policies and practices.

    The Organiser reserves the right to disqualify any Application made in breach of these Terms and to reject any Application which it reasonably believes may be or become in breach. The Organiser reserves the right to require evidence in such form as the Organiser may reasonably require of any Applicant’s compliance with any of these Terms and to disqualify any Applicant or Participant who cannot provide such evidence reasonably promptly.

    1.4 Multiple applications are not permitted.

    1.5 Applications may not be submitted by an agent whether acting on behalf of an undisclosed principal or otherwise.

    1.6 The Contest is NOT open to:

    1.6.1 Any person or entity who is a resident or national of any country which is subject to sanctions, embargoes or national trade restrictions of the United States of America, the European Union or the United Kingdom;

    1.6.2 Any employee, director, member, shareholder (as appropriate) or any of their direct families (parents, siblings, spouse, partner, children) (“Direct Families”) of the Organiser and Sponsors; or

    2.1 Each Applicant must fully complete and submit a RoadTest Application by the Application Close.

    2.2 By submitting a Registration Form, each Applicant:

    2.2.1 Authorises the Organiser to use his or her personal data (as defined in the Data Protection Act 1998) for the purposes of running and promoting the RoadTest;

    2.2.2 Authorises the Organizer to copy, reproduce and publish their application should they be accepted as a Participant;

    2.2.3 Will be deemed to have read, accepted and agree to be bound by these Terms. Applicants are advised to print and keep safe these Terms;

    2.2.4 Authorises the Organiser to copy, reproduce and use the Application and/or Review for the purposes of the RoadTest and as otherwise contemplated by these Terms. The Organiser will not be responsible for any inaccuracy, error or omission contained in any reproduction or use of the Project Blogs.

    2.2.5 Licenses the Organiser to use the intellectual property in the Project (IP) for the purposes of this Contest. As between the Applicant and the Organiser the IP remains owned by the Applicant.

    2.2.6 Grants the Organiser the right to use his or her likeness, photographs, logos, trademarks, audio or video recordings without restriction for the purposes of Contest or the promotion of it or the Site;

    2.2.7 Agrees to participate positively in all publicity surrounding the Contest;

    2.2.8 Agrees to be responsible for all expenses and costs incurred by him or her in preparing for, entering and participating in the Contest (save for any expenses expressly agreed by the Organiser to be borne by it in these Terms);

    2.2.9 Confirms that he or she owns all IP used in his or her application or Project or Blogs and indemnifies the Organiser from any claim by a third party that use of any material provided by an Applicant to the Organiser infringes the intellectual property rights of any third party;

    2.2.10 Agrees not to act in any way or fail to act in any way or be associated with any cause or group which would have a negative impact on the reputation of the Organiser and/or the RoadTest.

    2.3 All applications submitted to this RoadTest must meet the following criteria:

    2.3.1 Applicants must be the author, creator and owner of the proposed review idea. Applicants must not submit someone else’s idea;

    2.3.2 The proposed application must be reasonably achievable by the within the time constraints of the Contest;

    2.3.3 Applications must not include or propose any of the following, the inclusion of which shall render any proposed application ineligible:

    (a) Applications which relate to socially taboo topics, such as illicit drug use or sexual gratification;

    (b) Applications that are or could reasonably be considered to be illegal, immoral, discriminatory or offensive as determined by the Organiser;

    (c) Applications in relation to them which if accepted would infringe or breach any of the policies or terms of access or use of the Site.

    2.4 No Application may contain any of the hazardous substances identified by Article 4 of Directive 2002/95/EC of the European Parliament on the Restrictions on the Use of Substances in Electronic and Electrical Equipment ("the Directive") or the use of such hazardous substances in the in any such Project must not exceed the maximum concentration values set out in the Directive.

    3.1 Winners will be selected by the Organiser on the basis of the quality of his or her application and its adherence to these Terms.

    3.2 The total number of Winners selected will be at least the minimum number set out above but the actual number is at the sole discretion of the Organizer and/or the Sponsor, if applicable.

    3.3 The Organiser will use all reasonable efforts to announce the Winners via an update to the RoadTest page by the date listed above.

    3.4 Winners agree to take part in all publicity which the Organiser or the Sponsor wishes to use to promote the RoadTest, the Products featured or other Contests with which the Organiser may be connected from time to time.

    3.5 Details of the Winners may also be published in the media.

    3.6 Winners are responsible for all applicable taxes, duties or other charges payable in relation to any prize.

    3.7

    4.1 The Organiser hereby excludes all and any Liability arising out of the Contest or the acceptance, use, quality, condition, suitability or performance of any Prize, even where that Liability may arise from the Organiser’s negligence.

    4.2 Nothing in these Terms will affect any Liability of the Organiser for death or personal injury arising from its negligence, for breach of Part II of the Consumer Protection Act 1987 (in the event that any entrant is entitled to claim rights under the Consumer Protection Act 1987) or for any matter in relation to which it would be illegal for the Organiser to exclude or to attempt to exclude its Liability.

    4.3 Subject to 4.2, neither the Organiser, any parent company nor any subsidiary of the Organiser or such parent company or any of their directors, officers and employees (together referred to in these terms and the ‘Associates’) makes any guarantee, warranty or representation of any kind, express or implied, with respect to this Competition or the Prizes potentially available under it. Neither the Organiser nor any of its Associates shall be responsible for any Liability that may arise out of or in connection with person’s participation in this Competition, the claiming, redemption or value of any prizes under it, the use or enjoyment of such prizes or any events or circumstances arising out of or in connection with any of them. Any implied warranties of condition, merchantability or suitability or fitness for purpose of any of them are hereby expressly excluded. Wherever used in these Terms, ‘Liability’ shall mean any and all costs, expenses, claims, damages, actions, proceedings, demands, losses and other liabilities (including legal fees and costs on a full indemnity basis) arising directly or indirectly out of or in connection with the matter concerned.

    5.1 The RoadTest is organised and sponsored by the Organiser. The Organiser reserves the right to delegate all or any of its powers, rights and obligations arising in relation to the RoadTest to any Associate and certain such rights and powers are assumed by the Organiser on behalf of itself and each Associate. Reference to “Organiser” shall be deemed to include reference to each Associate.

    5.2 The RoadTest may be terminated at any time if there are, in the sole opinion of the Organiser, an insufficient number of entries, or if the Applications are not of an appropriate standard for a competition of this nature. The Organiser has the right to cancel or suspend the RoadTest at any time due to circumstances outside its reasonable control.

    5.3 The Organiser shall have the sole discretion to disqualify (without correspondence or right of appeal) any Applicant it considers to be adversely affecting the process or the operation of the RoadTest or to be in breach of these Terms or to be acting in a disruptive manner or with intent to annoy, abuse, threaten or harass any other Applicant or Participant.

    5.4 The Organiser has the right to amend or add to these Terms from time to time. Revised Terms and Conditions will be posted on the Contest Site and it is a condition of entry to the RoadTest that Applicants agree to comply with these Terms and, if appropriate, such Terms as amended from time to time.

    5.5 Headings are for convenience only and do not affect the interpretation or construction of these Terms and Conditions.

    5.6 These Terms and the operation of the Contest shall be governed by and construed in accordance with English Law and any claim or matter arising under these Terms shall be subject to the exclusive jurisdiction of the English courts.

    Important Dates

    Enrollment Begins: Jan 8  2018

    Enrollment Ends: Feb 12 2018

    RoadTesters Selected: Feb 21 2018

    Product Shipped: Feb 22 2018

    RoadTesting Begins: Mar 2 2018

    Reminder/Update Email: Apr 2 2018*

    Submit Reviews By: May 2 2018*

     

    *The element14 RoadTest Staff will send this reminder/update email.

    **If a RoadTester is unable to meet the deadline, please notify the RoadTest Program Lead, rscasny, as soon as possible before the deadline.

    Unboxing Video

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    1. Introduction

    Power is a requirement for every piece of equipment or product developed, whether it's from a large original equipment manufacturer (OEM) or a maker building his next home automation project. If you are a maker or a DIY hobbyist, you may have asked yourself, "What should I know about electrical power that would help me in my next project?" This learning module hopes to answer that question, as well as some fundamental questions about electrical power: what it is, and tips for using it in projects. This learning module will also highlight a variety of power solutions, which can be an off-the-shelf product (AC/DC power supplies, DC/DC converters, etc.) or discrete power converters (magnetics, passives, and semiconductor devices). Finally, to provide the maker with a "jump start" (pun intended) on his or her electrical power knowledge, this learning module will list and define best power practices, power considerations, and power design tips for the maker.

    2. Objectives

    Upon completion of this module, you will be able to:

    Discuss power fundamentals in AC and DC circuits; the difference between apparent, reactive, and real power; sinusoidal and non-sinusoidal waveforms

    Describe line-commutated and pulse-width modulated (switching) power

    Identify the common types of passive and semiconductor components used in power designs

    Understand the power architectures for common Maker boards

    List and define best practices, power considerations, and design tips for the Maker

    3. Fundamentals Review

    What is power? Most people would say it is watts. While that is true to some degree, power is more than the unit of measurement, watts. In physics, power is the rate of doing work per unit of time (e.g., one joule per second). Electrical power is the rate by which electrical energy is transferred from an electrical circuit (e.g., spinning a motor under load). In this section, we will discuss power fundamentals and review the main concepts and terms regarding both AC and DC power.

    - 3.1 Power in DC Circuits

    Figure 1: Simple DC Circuit

    Direct current (DC) is used as a power supply for electronic systems. A direct current circuit is an electrical circuit that consists of any combination of constant voltage sources, constant current sources, and resistors.  Figure 1 on the left is an example of the most basic DC circuit.

    The battery is the constant DC energy source of the circuit and delivers power to the load (RL). The power or electrical energy supplied by the battery is the product of source voltage and circuit current and is described in the following equation:

     

    Power (watts) = Voltage (volts) x Current (amps)

    The actual power delivered to the load is the power at the source minus any transmission losses, RLosses (for example, due to the resistance of the wire). For simple DC circuits, transmission losses can be negligible. However, long cable runs or other losses can impact true power at the load as well as the efficiency of the circuit.

    While the electrical power of an electric circuit or a circuit component is measured in watts, it actually represents the rate at which energy is converted from the electrical energy of the moving charges to some other form, for example, heat, mechanical energy, or energy stored in electric fields or magnetic fields. In electronics, it is common to refer to a circuit that is powered by a DC voltage source, such as a battery or the output of a DC power supply, as a DC circuit or a DC-powered circuit.

    - 3.2 Power in AC Circuits

    In alternating current (AC) circuits, the electricity or current flow alternates directions. Like DC power, the instantaneous electric power in an AC circuit is given by P = VI, but these quantities are continuously varying, which changes the way power in an AC circuit is determined.

    To better understand the above point, let's discuss how current flows in a DC circuit. A magnet near the wire in a DC circuit attracts the electrons on its positive side and repels the electrons on its negative side. This causes the electricity to flow in one direction only; DC power from a battery works this way (Figure 1). However, DC is not an efficient way to transfer electricity over long distances, because it begins to lose energy due to the power dissipated from the resistance of the circuit wires or cables.

    Figure 2: Generating an AC current

    In an AC circuit, current flow is generated using rotating magnets instead of applying magnetism along the wire. When the magnet is facing one direction, the electricity flows in that direction. When the magnet is flipped, the flow of electricity changes direction as well (Figure 2). Thus, the voltage oscillates in AC circuits, while voltage in a DC circuit is constant.

    Unlike a DC circuit, where circuit current and voltage are constant with a given RL, the voltage and current in an AC circuit vary and are not in phase with each other due to the inductance and capacitance, that is, the reactive components of the AC circuit (Figure 3).  This changes how power in an AC circuit is determined.

     

    Figure 3: Phase relationship of voltage and current in an AC circuit

    Since the instantaneous power in an AC circuit is constantly changing, it's harder to calculate. It's easier to determine the average value of instantaneous power in an AC sinusoidal circuit, using the following:

     

    Pavg = VI cos Φ

    where V and I are the sinusoidal RMS values, and Φ is the phase angle between the voltage and the current. Power in an AC circuit is also measured in watts.

    - 3.3 Effective / RMS Values / Average / Peak Values

    The values of voltage and current in a DC circuit are constant, so there is no issue in evaluating their magnitudes, but in an AC circuit, the alternating voltage and current vary from time-to-time, so it is necessary to evaluate their magnitudes. Three ways (peak value, average value and RMS value) have been adopted to express the magnitude of the voltage and current in an AC circuit.

    We've already discussed that the average power in an AC circuit is given by the equation, Pavg = VI cosΦ, where Φ is the phase angle between the voltage and the current (effective or RMS values). An effective or RMS value is equivalent to the value of the direct current that would produce the same average power dissipation in a resistive load. We've mentioned in the previous section that the term cos Φ is the phase angle between the voltage and current; this term is also called the "power factor" for the circuit.

    Figure 4: Peak Value of AC Current

    Finally, let's talk about the peak value, which is the maximum value attained by an alternating power source during one cycle (Figure 4). It is also known as the maximum value, maximum amplitude, or crest value.

    - 3.4 Apparent, Reactive, and Real Power

    Power in an electric circuit is the flow rate of energy past a given point of the circuit. In AC circuits, there are three classifications of power: real (true), reactive, and apparent (Figure 5).

    Figure 5: The power triangle expressing the relationship between real (true), reactive and apparent power. Note: As reactive power is decreased, the power factor angle approaches 0 degrees, which at this point, the circuit is most efficient.

    Real (True) Power: Active power is that portion of power, averaged over a complete cycle of the AC waveform, and resulting in the net transfer of energy in one direction.  It is more commonly known as "real" power in order to avoid ambiguity, especially in discussions of load with non-sinusoidal currents.

    Reactive Power: In alternating current circuits, energy storage elements, such as inductors and capacitors, may result in periodic reversals of the direction of energy flow. The portion of power due to stored energy, which returns to the source in each cycle, is known as reactive power. It's measured in the unit of Volt-Amps-Reactive (VAR).

    Apparent Power: This is power in an AC circuit which combines both, real power and reactive power. It's measured in Volt-Amps (VA).

    - 3.5 Power Factor (Efficiency)

    The ratio of active (real) power to apparent power in a circuit is called the power factor. For two systems transmitting the same amount of active power, the system with the lower power factor (cos Φ) or higher phase angle will have higher circulating currents, due to energy that returns to the source from energy storage in the load. These higher currents produce higher losses and reduce overall transmission efficiency.

     

    Figure 6: Power Factor Efficiency

    Phase Angle (Φ) Cos (Φ) Efficiency
    0 1 Very High
    45 .707 Moderate
    90 0 Very Low

    A lower power factor circuit will have a higher apparent power and higher losses for the same amount of active power. The power factor is 1.0 when the voltage and current are in phase. It is zero when the current leads or lags the voltage by 90 degrees (Figure 6). Power factors are usually stated as "leading" or "lagging" to show the sign of the phase angle of current with respect to voltage. Voltage is designated as the base to which current angle is compared, meaning that we think of current as either "leading" or "lagging" voltage. Where the waveforms are purely sinusoidal, the power factor is the cosine of the phase angle (Φ) between the current and voltage sinusoid waveforms.

    Example: The active power is 700W and the phase angle between voltage and current is 45.6°. The power factor is cos(45.6°) = 0.700. The apparent power is then: 700W / cos(45.6°) = 1000 VA

    For instance, a power factor of 68 percent (0.68) means that only 68 percent of the total current supplied is actually doing work; the remaining 32 percent is reactive.

    - 3.6 Power for Sinusoidal and Non-Sinusoidal Waveforms

    Figure 7: Phase Shift of Since and Cosine Functions

    A sine wave is the graph of the sine function, usually with time as the independent variable. A cosine wave is sinusoidal. It has the same form but it has been phase-shifted one-half π radians (Figure 7).

    Conversely, a non-sinusoidal waveform is one that is not a sine wave and is also not sinusoidal (sine-like). This may sound like a minor distinction, but there are actually some substantive implications.

    Figure 8: Examples of Non-Sinusoidal Waveforms

    A non-sinusoidal waveform is typically a periodic oscillation (Figure 8). Some examples are triangle waves, rectangle waves, square waves, trapezoid waves, and saw tooth waves. Non-sinusoidal waveforms are prominent in the world of electronics and they are readily synthesized. A non-sinusoidal waveform can be constructed by adding two or more sine waves.

    Although the sine wave is the ideal wave-form and is closely approached in modern alternators operating at no-load, the load conditions in generators and commercial circuits frequently cause considerable deviations from the sine wave.

    The widespread use of power electronic devices (such as different kinds of rectifiers and converters) for electric drives and other industrial load control usually results in heavy distortion of the sine waves of currents and also voltages.

    4. Power Supplies

    In this section, we will cover two important classifications of electronic power supplies: line-commutated and pulse width modulated.

    - 4.1 Line-Commutated

    A converter is a power conversion stage for control and conversion of electrical energy that utilizes power semiconductor devices (electronic switches, e.g., thyristors or transistors) controlled by signal electronics.

    In contrast to forced-commutated converters, line-commutated converters (naturally commutated converters) do not require active turn-off semiconductor switches but can use thyristors, which can only be forced to turn on. Thyristors operate in single-phase, as well as three-phase AC power grids in which the current in one thyristor becomes zero before another thyristor is turned on (discontinuous operation), or the thyristor current is forced to zero by turning on another thyristor, because the load current changes from one thyristor to the other one (commutation).

    Figure 9: Line-commutated, single-phase full-wave controllable rectifier using thyristors. The dotted line part of the graph illustrates that varying the triggering current to the SCRs.When these devices turn on in the AC half-cycle, the average power delivered to the load can be changed.

    A converter which is used to convert single-phase or three-phase AC voltage to DC voltage is called a rectifier. There are two kinds of rectifiers: controllable and uncontrollable rectifiers. A rectifier is controllable if the electric "valves" or switches, e.g., thyristors/silicon controlled rectifiers (SCRs), can be forced to turn on by control signals (Figure 9). A rectifier whose electric "valves" are all diodes is an uncontrollable rectifier. Using controllable rectifiers, the output quantities can be adjusted. A controllable rectifier can also be used to convert energy from DC voltage to a single-phase or three-phase AC grid. In this, case the rectifier is operating in the inverting mode.

    - 4.2 Pulse-width Modulated

    Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a modulation technique used to encode a message into a pulsing signal. Although this modulation technique can be used to encode information for transmission, its main use is to allow the control of the power supplied to electrical devices. The most common type of power supply today is the switching supply. These units use pulse-width modulation (PWM) to regulate output.

    A switch-mode power supply converts the AC line power directly into a DC voltage without a transformer, and this raw DC voltage is then converted into a higher frequency AC signal, which is used in the regulator circuit to produce the desired voltage and current. This results in a much smaller, lighter transformer for raising or lowering the voltage than what would be necessary at an AC line frequency of 60 Hz. These smaller transformers are also considerably more efficient than 60 Hz transformers, so the power conversion ratio is higher.

    MAX17572 EVM High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation

    An example of this type of power supply is Maxim Power Solutions' high-efficiency switching regulator IC. It provides longer battery life, generates less heat, and requires less board space. The MAX17572 is a high-efficiency, high-voltage, synchronous step-down DC-DC converter with integrated MOSFETs that operates over a 4.5V to 60V input. The converter can deliver up to 1A and generates output voltages from 0.9V up to 0.9 x Vin. It's typically applied in a variety of industrial control power supplies and point-of-load applications.

     

    MAXM17503 DC-DC Step-Down Power Module Evaluation Kit

    When you would like reduce the number of components in your power supply design, then power modules should be applied. They enable cooler, smaller and simpler power supply solutions. This step-down power module combines a switching power supply controller, dual n-channel MOSFET power switches, fully shielded inductor, and the compensation components in a low-profile, thermally-efficient, system-in-package (SiP).

    The MAXM17503 evaluation kit is a demonstration circuit of the MAXM17503 high-voltage, high-efficiency, current-mode scheme, synchronous step-down DC-DC switching power module.

    The device operates over a wide input voltage range of 4.5V to 60V and delivers up to 2.5A continuous output current with excellent line and load regulation over an output voltage range of 0.9V to 12V. The device only requires five external components to complete the total power solution. The high level of integration significantly reduces design complexity.

     

    MIC2295 Analog Switching Regulator

    Another example is the MIC2295 analog switching regulator by Microchip Power Solutions, which is a 1.2Mhz, PWM DC/DC boost switching regulator. High power density is achieved with the MIC2295's internal 34V / 1.2A switch, allowing it to power large loads in a tiny footprint. The MIC2295 offers internal compensation that offers excellent transient response and output regulation performance.

     

    MIC22950 10A Synch Buck Reg Eval Board

    The MIC22950 Evaluation Board was developed to evaluate the capabilities of the MIC22950 high-efficiency, 10A integrated switch, synchronous buck (step-down) regulator. The MIC22950 achieves over 95% efficiency while still switching at 2MHz over a broad load range.

    Considering the multiple DC voltage levels required by many electronic devices, designers need a way to convert standard power-source potentials into the voltages dictated by the load. Voltage conversion must be a versatile, efficient, and reliable process. Switch-mode power supplies are frequently used to provide the various levels of DC output power needed for modern applications, and are indispensable in achieving highly efficient, reliable DC-DC power-conversion systems. Here are a few of the most common types:

    Buck: The buck switching regulator is a type of switch-mode power supply that is designed to efficiently reduce DC voltage from a higher voltage to a lower one.

    Boost: The boost converter is a type of switch-mode power supply that is designed to convert electrical energy from one voltage to a higher one.

    Buck-boost: A type of DC-to-DC converter that has an output voltage magnitude that is either greater than or less than the input voltage magnitude.

    Inverting: The inverting converter reverses the polarity of the input voltage, yet permits the output voltage to be higher or lower than the input.

    Split-rail: This power supply generates both positive and negative output voltages using a variety of topologies, including inverting buck-boost topology.

    5. Passive and Semiconductor Devices Used in Power Circuits

    While makers often will use off-the-shelf AC/DC power suppliers or DC/DC converters to power their projects, it's useful for them to get a better understanding of the components used in these power supplies. This section examines the common components, both passive and semiconductor, that typically are used in a power supply design.

    - 5.1 Capacitors

    Figure 10: Filter ripple in a half-wave and full-wave rectifier

    Capacitors can be used to smooth out voltage, a process also known as filter ripple (Figure 10). They can also be used as reservoirs for electrical energy storage, and to block DC current. A capacitor consists of two metal plates that are separated by an insulator, the dielectric. One of the most notable features of capacitors is that they resist voltage changes, so that if the voltage applied to a capacitor is suddenly changed, the capacitor cannot react immediately and the voltage across the capacitor changes more slowly compared to the applied voltage.

     

    AC Line Rated Ceramic Disc Capacitors

    Capacitors are commonly used in power supplies; the AC line rated safety capacitor on the left is a good example from Vishay Power Solutions. The capacitor consists of a ceramic disc which is silver plated on both sides. Connection leads are made of tinned copper clad steel having a diameter of 0.6 mm. Encapsulation is made of flame retardant epoxy resin in accordance with UL 94 V-0.

    There are various types of capacitors available today, depending on their construction and the materials used. Some of the most common types are dielectric, film, ceramic, electrolytic, glass, tantalum, and polymer. In power designs, the most common types are electrolytic and polymer capacitors.

    Types: Aluminum, Ceramic Disk, Film, Glass, Multi-Layer Ceramic Chip, Multi-Layer Ceramic Radial, Super Capacitor and Tantalum

    - 5.2 Diodes

    Figure 11: Full Wave Rectifier with Center-Tapped Transformer

    A diode can be likened to a one-way valve. When voltage is applied to it — that is, when it is forward-biased and turned on — it allows current to flow in one direction but not in the other direction. This process is also called the rectifying process (Figure 11). One end of a diode is called an anode (triangle side of the symbol) and the other a cathode (bar side of the symbol). Most diodes allow current to freely flow from anode to cathode.

     

    SiC Schottky Barrier Diodes

    SiC is a compound semiconductor comprised of Silicon (Si) and Carbon (C). Compared to conventional Silicon Power Devices, SiC Power Devices deliver higher voltage breakdown, lower ON resistance, faster switching, and higher temperature operation. This translates to lower switching losses, reduced power loss, and smaller module size, allowing designers to make more robust products using fewer components.

    ROHM SiC Schottky Barrier Diodes are majority carrier devices featuring ultra-fast reverse recovery. As a result, switching loss is reduced, enabling high-speed switching operation. In addition, unlike silicon-based fast recovery diodes where the reverse recovery time (trr) increases with temperature, SiC devices maintain constant characteristics that improve performance.

    Types: Bridge Rectifiers, Power, Rectifiers, Schottky, TVS/ESD Protection and Zener

    - 5.3 Inductors

    Inductors, or induction coils, store electrical energy in a magnetic field. Inductors play an important role in power designs and are simply a coil of wire wrapped around a core, which is composed of iron, ferrite, or simply air. They act as an open circuit at first when DC (direct current) is applied to them, but after a while they freely allow it to pass. They oppose current changes. They are also commonly referred to as coils. Chokes are another name for a specific type of inductor which blocks or "chokes" high frequencies, while allowing low frequencies to pass.

    IHLP® - Low-Profile, High-Current Inductors

    A good example of inductors used in voltage regulator module (VRM) and DC-to-DC converter applications is Vishay Power Solutions' IHLP® low-profile, high-current inductors.

    The IHLP inductor is constructed using an "open" or "air coil" inductance coil. The two ends of the coil are connected to a lead frame that acts as the final termination pads. A powdered iron core is pressed around the inductor coil after the inductor coil is  welded to the lead frame. The characteristics of the powdered iron enhance the magnetic properties of the inductor and also give the inductor its final shape or footprint.

    Types: Chip Inductors, Leaded Inductors, Power Inductors and RF Inductors

    - 5.4 Integrated Circuits

    In power electronics applications, a power semiconductor is specifically designed to carry currents larger than 100 mA in an on-state and block voltages greater than 10 V in an off-state. They are generally used as switches, or in the case of a diode, as a rectifier or clamp. For some devices, the state of the device can be controlled by an external signal and, for others, the state is determined by circuit parameters (e.g., uncontrolled). Some of the controllable devices are "latching" devices, meaning that they only turn off when the conducting current returns to zero (e.g., commutation).

    Low Dropout Linear Regulators (LDO)

    Low dropout linear regulators (LDO) are used for or powering general-purpose portable devices. A good example of an LDO is Microchip Power Solutions' MIC5501/2/3/4.

    This LDO family is an advanced general-purpose LDO ideal for powering general-purpose portable devices. The MIC5501/2/3/4 family of products provides a high-performance 300mA LDO in an ultra-small 1mm x 1mm package. The MIC5502 and MIC5504 LDOs include an auto-discharge feature on the output that is activated when the enable pin is low. The MIC5503 and MIC5504 have an internal pull-down resistor on the enable pin that disables the output when the enable pin is left floating. This is ideal for applications where the control signal is floating during processor boot up.

    Types: Battery Management, Boost, Buck, Buck/Boost, Charge Pumps, DDR Termination, Digital Power Controllers, Diodes, FET Drivers, Flyback, Hot Swap, Integrated Sequencers, LDO, LED Drivers, MOSFETs, Multi-Phase, Off Line (AC/DC), PFC, PMICs, POE, and VRM

    - 5.5 Magnetics

    Typically, inductors are shielded so that their magnetic fields do not interact with other components in the same circuit. However, if we place two unshielded inductors side-by-side and feed one of them with AC (alternating current), then its magnetic field induces a voltage not only in the AC current applied inductor, but also in the other inductor, despite the fact that the latter inductor is physically close, but not electrically connected, to the former inductor. The process of inducing voltage in the second inductor is called mutual inductance. So, if you pass current in one inductor, you create voltage in the inductor near it.

    A transformer is nothing more than two inductors, or coils, wound around the same core material so that mutual inductance is at a maximum level. The coil that lets the current pass is called a primary coil, and the coil that is induced with voltage is called a secondary coil.

    A transformer can electrically isolate two circuits and also step voltages up or down. Alternating current voltage can be increased (stepped-up) or decreased (stepped-down) using a device called a transformer. The turns ratio of a transformer is the ratio of the number of turns of windings between the primary and secondary. The turns ratio determines whether the transformer is a step up or step down transformer (Figure 12).Transformers reduce the high voltage of AC to a lower voltage for use in home appliances. (While Thomas Edison's work led to the DC battery system, Nikola Tesla came up with the AC generator by using a rotating magnet).

    Figure 12: Comparison of turns ratio in a step-up and step-down transformer

    Types: AC Line Filters, Broadband Modules, Chokes, Current Sense, Filtered RJ Jacks, LAN Modules, Power Magnetics, Telecom Modules, and Transformers

    - 5.6 Resistors

    Resistors are the most commonly used electronic component. Their role is simply to restrict the flow of electrical current when necessary and make sure that the correct voltage is supplied to a component. Resistance is measured in ohms Ω.

    Types: Carbon, Chip, Chip Resistor Array, Current Sense, Film, Trimmer Pots, and Wirewound

    - 5.7 Transistors

    The transistor is considered to be the biggest technological discoveries or innovations of the 20th century. Indeed, inside every electronic device nowadays you will find transistors working effortlessly and reliably. The two most common types of transistors are bipolar junction transistors (BJTs), which can be broken down into NPN and PNP transistors, and field effect transistors (FETs). Similar to BJTs, FETs come in N-channel and P-channel types. The two major types of FETs are MOSFETs (Metal-Oxide Semiconductor FETs) and JFETs (Junction FETs).

    Types: Darlington, High Voltage > 500 V, IGBTs, NPN, PNP and Small Signal

    6. Power Architecture Overview for Common Maker Boards

    - 6.1 Raspberry Pi 3 Model B

    The Raspberry Pi 3 is powered by a +5.1V Micro USB supply. Purchasing a 2.5A power supply from a reputable retailer will provide you with ample power to run the Raspberry Pi. You can also purchase the official Raspberry Pi Power Supply.

    Power requirements by product:

     

    Product Recommended PSU Current capacity Max total USB peripheral draw Typical bare board current consumption
    Raspberry Pi Model A 700mA 500mA 200mA
    Raspberry Pi Model A+ 700mA 500mA 180mA
    Raspberry Pi Model B 1.2A 500mA 500mA
    Raspberry Pi Model B+ 1.8A 600mA/1.2A (switchable) 330mA
    Raspberry Pi 2 Model B 1.8A 600mA/1.2A (switchable) 350mA
    Raspberry Pi 3 Model B 2.5A 1.2A 400mA

    Typically, the model Raspberry Pi 3 Model B uses between 700-1000mA depending on what peripherals are connected; the model A can use as little as 500mA with no peripherals attached. The maximum power the Raspberry Pi can use is 1 Amp. If you need to connect a USB device that will take the power requirements above 1 Amp, then it must be connected to an externally-powered USB hub.

    The power requirements of the Raspberry Pi increase as you make use of the various interfaces on the Raspberry Pi. The GPIO pins can draw 50mA safely, distributed across all the pins; an individual GPIO pin can only safely draw 16mA. The HDMI port uses 50mA, the camera module requires 250mA, and keyboards and mice can take as little as 100mA or over 1000mA! Check the power rating of the devices you plan to connect to the Pi and purchase a power supply accordingly.

    Official Raspberry Pi Power Supply with Universal Heads

    Please also be aware that some hubs will backfeed the Raspberry Pi. Backpowering occurs when USB hubs do not provide a diode to stop the hub from powering against the host computer. Other hubs will provide as much power as you want from each port. This means that the hubs will power the Raspberry Pi through its USB input cable, without the need for a separate Micro-USB power cable, and bypass the voltage protection. If you are using a hub that backfeeds to the Raspberry Pi and the hub experiences a power surge, your Raspberry Pi could potentially be damaged.

    - 6.2 Arduino Due

    The Arduino Due can be powered via the USB connector or with an external power supply. The power source is selected automatically. External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the GND and Vin pin headers of the POWER connector. The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply fewer than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts. The power pins are as follows:

    Vin: The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or if supplying voltage via the power jack, access it through this pin.

    5V: This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the Vin pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.

    3V3: A 3.3-volt supply generated by the on-board regulator. Maximum current draw is 800 mA. This regulator also provides the power supply to the SAM3X microcontroller.

    GND: Ground pins.

    IOREF: This pin on the Arduino board provides the voltage reference with which the microcontroller operates. A properly configured shield can read the IOREF pin voltage and select the appropriate power source or enable voltage translators on the outputs for working with the 5V or 3.3V.

    - 6.3 BeagleBone

    There are several ways to power a BeagleBone. The option exists to feed the on-board regulators through either the barrel connector input or USB input. When powered up over USB, the regulators are somewhat limited in what they can supply to the system. Power over USB is sufficient as long as the software and system running perform some management to keep it under the USB current limit threshold.

    BeagleBone Black

    For simplicity and maximum capability, powering over the 5V barrel connector is typically recommended. The power adapter is required to provide 5V over a 5.5mm outer diameter and 2.1mm inner diameter barrel connector (a barrel connector length of 9.5mm is more than sufficient). The recommended supply current is at least 1.2A (or 6W), but at least 2A (or 10W) is recommended if you are going to connect anything over the USB. The actual power consumption will vary greatly with changes on the USB load.

    BeagleBone® Blue

    The BeagleBone® Blue is the affordable and complete robotics controller built around the popular BeagleBone open hardware computer. Power management: TPS65217C PMIC is used along with a separate LDO to provide power to the system (Integrated in the OSD3358); 2 cell (2S) LiPo battery charger (powered by 9 - 18VDC DC Jack) and 6VDC 4A regulator to drive servo motor outputs. Power source - microUSB USB, 2 cell (2S) LiPo battery JST-XH connector or 9 - 18VDC DC Jack.

    - 6.4 BitScope Blade QUATTRO

    The BitScope Blade is a blade server solution built using Raspberry Pi designed for physical computing. The Raspberry Pi is a very reliable physical computing platform when powered correctly. The BitScope Blade Quattro provides power & mounting for four Raspberry Pis (Raspberry Pi not included). The key to using it in embedded, industrial, and server applications is to have a rugged, reliable power & convenient mounting solution for one or more Raspberry Pi in racks and other industrial configurations.

    The BitScope Blade is tailor made to offer this in a range of cost-effective blade boards. Whether it's a rack full of Raspberry Pi to build low cost cloud platforms, build farms or test, measurement and data acquisition systems, or even just a single Raspberry Pi and optional HAT, BitScope Blade offers a range of unique solutions. BitScope Blade is capable of delivering up to 4A current and is compatible with DC power sources ranging from 9V to 48V.

    Almost any deployment scenario will work, because the BitScope Blade supports most common DC power sources. While BitScope Blade started life as Blade Server for Raspberry Pi, it has since evolved into a full range of power, mounting, and deployment solutions for Raspberry Pi, HATs, the Raspberry Pi Display, and of course, BitScope.

    - 6.5 MiniZed

    The MiniZed is a single-core Zynq 7Z007S development board. This board targets entry-level Zynq developers with a low-cost prototyping platform. The integrated power supply from Dialog generates all on-board voltages.  An auxiliary microUSB supply input can be used to power designs that require additional current.

    MiniZed supports the input and output voltages and currents shown below:

     

    Bank Voltage Current (A)
    Vccint/Vccpint 1 1.5
    Vccaux/Vccpaux 1.8 0.5
    Vcco (DDR) 1.35 1
    Vcco 3.3 3.3 1
    Vterm 0.68 0.5
    Vin 5 2.4

    PS and PL subsystems are powered from the same supplies to save board size and cost. Sequencing requirements are as follows: 1V → 1.8V → 1.35V/3.3V/0.68V

    MiniZed supports the input and output voltages and current. All supplies maintain monotonic rise. Input power is provided via a MicroUSB connector.

    These power figures reflect worst case consumption with a 7010 Zynq device populated. The 7007S device is standard on MiniZed; however, the board was designed to potentially support a 7010, hence the power system being designed to support the larger device. These figures do not include extra capacity to support powering a shield (3.3V at 500mA) or USB host mode (5V at 500mA). The Vin current requirement reflects the use of the Monoprice 14578 USB supply included in the Avnet AT&T cloud connect kit. This external supply is sufficient to support the addition of USB host mode, as well as powering a shield. This supply is a 2.4A 5V supply using a standard USB interface.

    7. Power Considerations and Tips for the Maker

    We cannot possibly cover all of these topics in depth, but want to give you an idea of basic power considerations and tips, and encourage you to do additional research as required.

    - 7.1 Cable Runs, Lengths

    The main concern here is voltage drops. Voltage drop on a lighting circuit in a 120V system isn't considered a major issue. The branch circuit currents are relatively low—usually 20A or below—and the standard wire sizes are usually large enough to minimize resistance problems.

    But voltage-drop issues can occur with lower voltage systems. Depending on its size and length, the conductor serving the fixtures of a low-voltage design acts as a resistor. As current runs through the conductor, a voltage drop occurs: the voltage at the end of the conductor is lower than at the source. Wires with smaller cross-sectional diameters (e.g., 20 AWG) that conduct higher currents will increase the voltage drop by raising resistance and increasing the fixture load, respectively.

    - 7.2 Terminations/Connectors

    Current ratings are important, since a signal connector failure can cause issues from a minor nuisance to shutting a system down; a power connector failure can lead to catastrophic failure, causing system or structural damage.

    Considerations:

    Wire-to-wire - heavily influenced by wire gauge

    Board-to-board - heavily influenced by PCB copper and overall size

    Current Rating - there is no one standard body to define common means of rating current; look to the supplier specs and compare

    Voltage - Look at geometry (creepage and clearance) and dielectric properties

    Environmental Factors - ambient temperature and system airflow

    - 7.3 Thermal Issues

    Quite often the power supply is the last item specified for many new designs. But just finding something that will fit a system power budget may not be "good enough" anymore. With the increasing demands for greater efficiency, high reliability, and faster design cycles, as well as increasing regulation, this approach may not always be acceptable.

    A good engineer will consider all aspects of power needs early in the project, including thermal dissipation, air flow, and packaging. Thinking about the power system early in the project is essential if the unpleasant surprises of needing a bigger supply or a new cooling strategy are to be avoided.

    Figure 13: Adding a heat sink or a cooling fan to the Raspberry Pi's Broadcom processor and memory chips can address thermal issues.

    - 7.4 Voltage Drops

    Common to all power supplies is the fact that they have internal conductors. These conductors (internal wiring) will act to drop voltage with current. This wiring will create a "real" series resistance. This is modeled as a series resistor, although there is no physical unit which causes the voltage drop.

    Batteries have another effect. Current is produced by electrochemical reactions, and these reactions can only occur so fast. In a lead-acid battery, for instance, sulfuric acid reacts with the lead/lead oxide terminals, and once the sulfuric acid has reacted new acid must take its place, which requires time. As a result, the maximum current is limited by the geometry of the battery plates, and this shows up as a drop in voltage when current increases. This is modeled as a series resistor, although there is no physical unit which causes the voltage drop.

    A good power supply these days will sense the output voltage and adjust the voltage of the internal source to compensate for internal voltage drops, and for slowly changing loads will approximate an ideal voltage source closely.

    - 7.5 Efficiency

    The size or power density of a power supply is a key criterion when selecting the optimal product for a given application. In applications where fans are not desirable due to noise or reliability concerns, efficiency becomes a primary concern.

    Power supply technology has evolved to a point where efficiencies in the 90-95% range are available. To put this into context, a typical power supply in the 1980s would have been in the region of 75% efficient. By considering efficiency as an important criterion, a designer can make fundamental design decisions that affect the overall system in a positive way by:

    Eliminating or reducing the need for system fan cooling

    Reducing the overall size and weight of the system

    Reducing the internal temperatures of the system and improving reliability

    Enhancing system reliability

    Reducing overall energy usage and the end user operating costs

    - 7.6 Noise Issues

    As power switching speeds and signal slew rates increase, and as the number of active pins on devices increase, more switching noise is induced in power supplies. At the same time, circuits are becoming more susceptible to power supply noise.

    Almost all noise comes from one of two sources: switching power supplies create their own undesired noise, usually at harmonics of the switching frequency or coherent to the switching frequency. When gates and output pin drivers switch, this action creates transient current demands on the power supplies. This is usually the primary source of noise in most digital circuits.

    Not all oscilloscopes can be used for measuring noise accurately. Because of the wide bandwidth of power supply noise, designers tend to choose oscilloscopes for measuring it. Real-time, wideband digitizing oscilloscopes and wideband scope probes have their own noise, which you must take into account. If the noise you're trying to measure on your power supply is of the same order as the noise floor for the scope and probe, you will be challenged to measure your noise accurately. Know how much noise your scope and probe contribute. Select a scope and probe with a sufficiently low noise floor to allow you to make your measurement accurately.

    - 7.7 Safety

    Safety directives and legislation specify the requirements for a power supply or converter, according to the final application. There are three main groups of directives: Protections, EMC/EMI Immunity, and Electrical Safety. The list below covers the main requirements for general, industrial, and specialized applications.

     

    Protections
    OVP Over-voltage protection, SELF/PELF
    OCP Over-current protection, overheating, fire
    SCP Short-circuit protection, hiccup/latching, fire
    OTP Over-temperature protection, overheating, fire
    IP Ingress protection scale on touch, dust and water protection
    Class I/II Protection against shock, w/wo protective earth
    SELV Safety/separated extra-low voltage
    PELV Protected extra-low voltage
    EMC/EMI Immunity
    CE EMC and safety LVD for EU directive 2004/108/EC
    CISPR22/EN55022 EMC for EU ICT, light industry, general, class A/B
    CISPR11/EN55011 EMC for EU heavy industry
    FCC Title 47 EMC for USA ICT, light industry, general
    IEC61000/EN55024 EMC/immunity
    Electrical Safety
    CE LVD low voltage directive 2014/35/EU
    EN60950-1 EU for ICT, light industry, general
    EN60601-1 EU for medical equipment 4th edition
    EN60335/UL1012 Household appliances
    EN60945 Marine applications
    UL508 USA for ICT, datacom, light industry
    CSA C22,2 CND for ICT, datacom, light industry
    EN50178/IEC62103 Electrical equipment power installations
    Special Environments
    EN50155/RIA12 EU railway standard on EMC
    EN50121 EU railway standard on immunity
    EN 60079 Ex II 3G hazardous locations
    CSA22,2/ANSI/ISA ATEX hazardous locations with classes
    IEC 60068 Shock and vibration tests

     

    MDS Series External Power Supplies

    External AC/DC power adapters are used in many different portable applications. A good example of an external power adapter is the MDS Series by Delta Electronics Power Solutions. They come with a universal input from 90 to 264 VAC. Product offerings range from 5W to 150W with full Medical safety certifications including Level VI efficiency and Medical EMC 4th Edition (IEC 60601-1-2:2014). The MDS series is certified for EMC standards according to EN 55011 for industrial, scientific and medical (ISM) radio-frequency equipment and EN 55022 for Information Technology Equipment (ITE) radio-frequency equipment.

    - 7.8 Grounding

    In electrical engineering, ground or earth has multiple functions, including (a) the reference point in an electrical circuit from which voltages are measured, (b) a common return path for electric current, or (c) a direct physical connection to the Earth. Connection to ground also limits the build-up of static electricity when handling electrostatic-sensitive devices.

    Isolation is a mechanism that defeats grounding. It is frequently used with low-power consumer devices, and when electronics engineers, hobbyists, or repairmen are working on circuits that would normally be operated using the power line voltage. Isolation can be accomplished by simply placing a "1:1 wire ratio" transformer with an equal number of turns between the device and the regular power service, but it also applies to any type of transformer using two or more coils electrically insulated from each other.

    For an isolated device, touching a single powered conductor does not cause a severe shock, because there is no path back to the other conductor through the ground. However, shocks and electrocution may still occur if both poles of the transformer are contacted by bare skin. Isolated power supplies do not provide any ground connection, and are designed to isolate the output from input.

    *Trademark. Avnet® is a trademark of Avnet Inc. Other logos, product and/or company names may be trademarks of their respective owners.

     

    Shop our wide range of power devices, including power modules, rectifier diodes, passive devices, magnetic components, integrated circuits and evaluation boards.

    Shop Now

     

    Test Your KnowledgeBack to Top

    Are you ready to demonstrate your power essentials for makers knowledge? Then take a quick 15-question multiple choice quiz to see how much you've learned from this Power Essentials 1 Learning Module.

    To earn the Power Essentials 1 Badge, read through the module to learn all about power essentials for makers, attain 100% in the quiz at the bottom, leave us some feedback in the comments section, and bookmark this page.

     

    1) Name the two types of power found in electrical circuits.





     

    2) Which of the following is not a common passive device used in power circuits?





     

    3) Which of the following is a type of safety protection for power supplies?



     

    4) In a direct current circuit, the power consumed is simply the product of the DC voltage times the DC current and is measured in watts. Which formula below relates to this statement?





     

    5) Fill in the blank: Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a modulation technique. Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a modulation technique used to encode a message into a pulsing signal. Although this modulation technique can be used to encode information for transmission, its main use ______________________________.





     

    6) Complete this sentence: The Raspberry Pi 3 is powered by a +5.1V micro USB supply; _____________________.





     

    7) Power supply technology has evolved to a point where efficiencies in the 90-95% range are available. A designer, by considering efficiency as an important criterion, can make fundamental design decisions that affect the overall system design in a positive way by:





     

    8) Choose the best answer from the selections below on the basic function of a Capacitor.





     

    9) True or False: As power switching speeds and signal slew rates increase, and as the number of active pins on devices increase, more switching noise is induced in power supplies. At the same time, circuits are becoming more susceptible to power supply noise.


     

    10) Which of the following is not a common semiconductor device used in power circuits?





     

    11) True or False: Isolation is a mechanism that defeats grounding. It is frequently used with low-power consumer devices, and when electronics engineers, hobbyists, or repairmen are working on circuits that would normally be operated using the power line voltage.


     

    12) True or False: Common to all power supplies is the fact that they have internal conductors. These conductors (internal wiring) will act to drop voltage with current. This wiring will create a "real" series resistance. This is modeled as a series resistor, although there is no physical unit that causes the voltage drop.


     

    13) A transformer is nothing more than two inductors, or coils, wound around the same core material so that mutual inductance is at a maximum level. A transformer can electrically isolate two circuits and also step voltages up or down. Which of the following is not a transformer?





     

    14) True or False: The Arduino Due can be powered via the USB connector or with an external power supply. The power source is selected automatically. External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery.


     

    15) Which of the following is not an electrical safety standard for power supplies?





    Alas, you didn't quite meet the grade. You only got %. Have another look through the course, and try again.
    You nailed it, and scored %! To earn the Power Essentials 1 Badge, leave us some feedback in the comments section and then download the attached Power Essentials for Makers 1 PDF for future reference. Other topics you want to learn? Send a suggestion.

    0 0
  • 01/18/18--07:25: Hey e14 Members who YouTube
  • I was wondering if any of you were talking about the current kerfuffle in the news surrounding youtube partner program changes.  Before drafting this note, i decided to search for youtube and see if there was already a conversation underway. 

     

    So I searched for youtube and the most recent poste i found was from gam3t3ch titled,  Youtube is the Devil which is ironic becase he posted it over 9 months ago.

     

    I digress.

     

    So members and Top Members I know many of you have channels (a short list is posted below).  I'm wondering what your thoughts are on what YouTube is doing to the small/just starting channels?  If you have a youtube channel - why did you start it up?  How does it feel to have your hopes and dreams of being the next PewDiePie snatched cruelly from your hands?

     

    Or do you just enjoy making videos?

     

    signed,

    just curious

     

    a short and very incomplete list:

    https://www.youtube.com/user/workshopshed Andy Clark - Workshopshed

     

    https://www.youtube.com/user/TheBreadboardca Peter Oakes - The Breadboard

     

    https://www.youtube.com/mayermakes - Clemens Mayer

     

    https://www.youtube.com/user/fvdbosch - Frederick Vandenbosch

     

    https://www.youtube.com/user/thewestcoasthippie Nico teWinkel

     

    https://www.youtube.com/user/enricomiglino/about Enrico Miglino

     

    https://www.youtube.com/channel/UCJ00i4FLwZG6IZmTGP0xIvg Ravi Butani

     

    https://www.youtube.com/channel/UC_CEc_vC8-i7gta98km5Qvg Charles Gantt

     

    https://www.youtube.com/channel/UCCJvsxwgHKCZqt9q7MM5QtA Cabe Atwell

     

    https://www.youtube.com/user/TheBiglesp Les Pounder

     

     


    0 0
  • 02/20/18--19:56: Car audio boom box
  • Hi all.

    Im doing a project with a jvc car audio set up.

    The idea is to set up a head unit. 2 6x9s and 2 6x6.

    Now the issue is to install an agm or slim line deep cycle battery to power the unit.

    The unit can be powered via 240v or 12v and also the 24v would charge the battery or a solar panel attatched to the rear of the box.

     

    Thought there would be a charge controller that would be able to switch these auto.

    But am told there isnt.

     

    Any help on the best way to work this would be greatly appreciated.

     

    Ashley


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    The Hack Like Heck Competition

    Do you like creating things with electronics?

    Do you like to make videos of the action?

    Are you the next Ben Heck?

    We want you!!

    About Hack Like Heck
    Content Partner Program
    The Prizes

     

    Act 1 - Auditions - with a couple of chances to win!

    We're looking for new talent to make videos for the element14 Community.  If you want to be the next Ben Heck, send us an audition tape! (Ok, it won’t really be a tape but a video file.)

     

    Everyone who submits an audition tape will receive a t-shirt from The Ben Heck Show.

     

    Act 1 submissions are due 9-March.  TEN Winners (selected from all auditions) will also receive:

    • The Bill of Materials of electronics as used in Ben’s build, delivered to your door
    • The chance to participate in an online conversation with the crew from The Ben Heck Show to ask questions about the build or get advice on filming your progress.

    Why are You Having Auditions?

     

    Do I have to submit an Audition Tape to enter Hack Like Heck?

     

    Tell Us. . .

    In the audition tape tell us these three things in a video less than 60 seconds long:

    1. How you would answer the viewer’s request and how that would make Ben’s build better?
    2. Tell us about your electronics experience (previous projects, school, work) that proves you have the skills to get this done (include a link to your YouTube channel, if you have one)
    3. And that you’re committed to turning this around by the submission deadline - because that’s the hardest part!

     

    Hack Like Heck - How to Submit your Audition Tape

    The audition tapes will be accessible to everyone on the element14 Community.


    Winners will be selected based on

    1. They covered all three things from the “tell us” list
    2. Quality of their video
    3. The overall love of electronics they ooze from the screen

     

    Why are You Having Auditions?  Who is this For?

    The element14 community is interested in expanding its sponsored video content and is looking for video content creators with a passion for electronics!

     

    Do I have to submit an audition tape to enter Hack Like Heck?

    NO.  Just Declare your Intention.

     

    Can You Still Enter the Contest If Your Audition Isn't In the Top 10?

    ABSOLUTELY!....you don't even need to submit an audition to be eligible to win the contest for the Grand Prize and Top Ten Prizes!


    0 0

    A group of researchers developed a system that could help improve the brain’s ability to recall events in patients with brain deterioration. However, it is too early for the technology to be used for Alzheimer’s patients. A Deep-Brain Stimulation device. (Image via IOS Press)

     

    The brain, the most mysterious organ in the human body, is constantly debated among neuroscientists. Recently, a team of researchers built a system that could help treat memory loss of challenges. The new discovery is based on a combination of Deep-Brain Stimulation and well-timed observation of the interactions between neurons. The experiment involved learning from the normal activities of the brain and artificially recreating those interactions. Researchers measured the electrical patterns in the brain of patients when they remembered something and compared it to the patterns when the patients could not remember.  What they learned is that there is an area of the brain, the lateral temporal cortex, which is instrumental in the mechanism of memory.  Ultimately, the results show that with the combination of DBS (Deep-Brain Stimulation) and the observations, patients could see an improve of their memory faculty by fifteen percent.

     

    However, Pr. Kahana of the University of Pennsylvania, who was leading the research team with Youssef Ezzyat, felt that those results were not enough to conclude that the system could be used for serious cases like Alzheimer’s disease. According to Kahana, the effects of DBS on the brain are only effective when the brain activity has slowed down. Despite his skepticism, some scientists like Professor Gwen Smith of the University of John Hopkins, are excited about the findings. She not only believes in the potential of Kahana’s research but also trusts in the method used to conduct it. She is supported in her opinion by Pr. Itzhak Fried, a neurosurgery expert of the University of California, who also believes that it will be safer to wait for improved outcomes from the study before drawing any conclusion regarding any possible cure for brain damages. One of Smith’s colleagues, Andres Lozano of the University of Toronto, thinks that even though DBS is effective only for short-term memory, Kahana’s team is onto something. According to Lozano, Kahana’s system might not be so invasive since it will help the brain heal itself. All these results inspired some researchers at NeuroPace to create a prosthetic device that should help epilepsy sufferers offset the effects of a seizure by preventing it.

     

    Meanwhile, some members of the science community are having other plans for the new discovery. This group of people believes that everybody might be able to use a boost of memory. One of them is Bryan Johnson, the head of a company focused on neurotechnology. Although he seems to appreciate the value of the implant, he might not totally grasp the costs, both physical and ethical, of the procedure. Dreaming of a general application of the technology of the implant is, however, forgivable given that the results of the research didn’t indicate that it was specifically designed for ill people. In addition, Fried who is against the extension of the implant to the public, might find peace knowing that not everyone can afford a brain surgery, for fun. And, even if someone could, learning about the possible dangers of it should cool the hunger for the procedure. At least, till the day surgical interventions on the brain are completely safe.

     

    While congratulations are in order for the advances in brain research, there is no denial that Kahana’s brain implant is not ready to be used on Alzheimer’s patients yet. The scientific community is certainly divided as far the possible uses of the device, but it will serve humanity best if they can attempt to work together, instead of chasing personal gains. The situation with current medications and all their side effects should be proof to scientists that the lives of the very people who rely on them for survival cannot be toyed with; certainly not for personal gain or ego.

     

    Have a story tip? Message me at: cabe(at)element14(dot)com

    http://twitter.com/Cabe_Atwell