Fail of the Week: Blown Light Bulb Controllers

fotw-nyc-resistor-chandelier-driver

We’ve been meaning to get around to this one for many weeks now. It’s been hard to find good fail write-ups… it’s as if hackers are afraid to admit that sometimes projects fail. We hope you’ll shake off that opinion as failure is the fastest path for learning and true understanding!

[xymax] was working on a control system for a chandelier with 150 bulbs which use 5 Watts each. This project was being readied for the NYC Resistor Interactive Party which [Adam Fabio] attended last month. As deadline for the show approached, the last piece was put in place late into the night… but it was connected backwards. In a tale worthy of a slapstick movie, the reverse polarity caused a chip on all seven controller boards for this module to blow like the one seen above. But that’s not all, the laptop being used during prototyping was connected by USB and started smoking!

All of us feel the pain of this type of equipment failure. Luckily [xymax] looked for lessons to learn instead of dwelling on the mistake itself. Use protection diodes, keyed connectors, and write about your failures. Hopefully reading this will help others avoid a similar equipment-destroying mistake.


2013-09-05-Hackaday-Fail-tips-tileFail of the Week is a Hackaday column which runs every Thursday. Help keep the fun rolling by writing about your past failures and sending us a link to the story — or sending in links to fail write ups you find in your Internet travels.

Comments

  1. camerin says:

    I am no historian, but i am pretty sure today is Thursday

  2. echodelta says:

    When connecting DC there is a coin toss every time. One bit of information and no redundant information base to infer from.

  3. jbb says:

    Oooh, ow, gotta hate cascading failures!

    Also, I’m always worried about connecting my laptop to power hardware, so my condolences for the magic smoke.

  4. DainBramage1991 says:

    A good candidate for a crowbar circuit. So simple, but so effective.

    • pcf11 says:

      A crowbar circuit you say? I’ve built those. The ones I’ve built have all been the common over-voltage variety though. This is a reverse polarity issue here. Something a common over-voltage crowbar circuit will do nothing to protect against. Maybe you meant another kind of circuit? If you did though it is one that I am not aware of. The article already mentioned the two things they could have done to prevent this from happening.

      • mauswerkz says:

        A crowbar circuit for reverse polarity can be made by simply using a reverse biased diode across the power supply input. It becomes forward biased if the supply is connected wrong, limits the voltage to -0.7v, and blows the fuse.

        • DainBramage1991 says:

          ^ This is exactly what I was referring to. It is common practice when working on DC powered radios (and other circuits) to add a diode across the power leads if one is not already present. Cheap insurance. A new fuse costs less than $1, a new radio costs hundreds.

          • pcf11 says:

            Sounds good. I know that the cost of fuses can add up though. When I’m blowing them, I’m usually blowing them by the box full until I get things sorted out.

  5. Peter says:

    Regarding a USB isolator, I was wondering whether a regular USB hub, powered or unpowered, provides any protection/isolation of the computer. Anyone know?

    • AKA the A says:

      It doesn’t, it has no way of doing it…
      Moral of the story – never combine power electronics and USB, use ethernet :D

      • Rollyn01 says:

        Unpowered, no. However, there are some powered ones that can provide some limited protection. I had one that did some time ago but I lost it. Wish I still had it too.

        • AKA the A says:

          Unless it has a massive crowbar circuit or the $20/pcs isolator IC, it will not do much :P
          With the cost of any USB isolation, a chinese ethernet shield knockoff might even be cheaper, yet you get decent galvanic isolation and 100m of possible cable length…

      • Shakipu says:

        You can blow you Ethernet connector if you add power to the Ethernet line and if your network card is not POE.

  6. Travis Kneale says:

    Another related lesson from my experience. Always put thous screw terminal in line they are significantly stronger that way. Expensive ones(ost makes good ones) are ok but the sub $.10 ones you want to put in line or they twist all over.

    • Tony says:

      I was wondering why you’d mount then on angles anyway, let alone half on top and half underneath.

      Soldering to a terminal block kinda misses the point too…

  7. strider_mt2k says:

    Doh! That’s cause for a “responsibility reminder” where I work.
    It sucks bad enough in an industrial setting, but in a project like this it’s heartbreaking.
    Sorry for the loss and best of luck with the next one!

  8. ds18s20 says:

    Keep on trucking, next time better luck, laptops are cheap now days

  9. NewCommentor1283 says:

    i gave an MP3 player an RF burn once …
    was trying to DIY amplify sound but started to oscilate…
    headphone out (of MP3 player) became an antenna and fried.

    thats why we dont use RF transistors to DIY audio amps!
    … or just add in RF supression, 10pf on B-C sound good?

    from now on i use an oldschool LED to tell me if something might RF burn me or something i might connect. the load being a short piece of wire.

  10. Alan says:

    In my early days, I thought “hollywood rubbish, never happens in real life”. In thirty years, I’ve seen a pyrotechnic failure ONCE…
    In an Air Traffic Control tower. That got a direct hit with a lightning bolt, to the receive antenna on the roof.
    Downstairs, the control racks arced to any nearby earth point, and power supply LEDs spat across the room. Spectacular, extremely lucky nobody was nearby – and a headache to repair.

  11. Marco says:

    Don’t use a diode, use an unidirectional TVS (and a fuse of course). Two failure modes covered with one component.

  12. Kit Scuzz says:

    Any chance we might re-title this segment “Hack a day: Lessons Learned” or for the comic nerds out there “Hack a day: A Lesson is Learned but the Damage is Irreversible”?

    I think part of the reason people are hesitant to submit is because “Fail of the week” with a bright red “FAIL” on the intro image makes people feel like you’re judging them as stupid or as failures overall. Even though you guys go to great lengths to point out that it’s about learning and overcoming, it doesn’t change the fact that the title and the images look threatening and demeaning to people who submit.

    A stamp which says: “Lesson Learned!” on the image with “Get Polarized Plugs!” as the article title is much more immediately grokkable as “people make mistakes, learn from it!”

    Also: I know I don’t document my failures as well as my successes. I have a tendency to be in a rush to fix issues and there for all the small fumbles are kind of glazed over unless there’s some sort of lasting impact on the design.

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