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Thread: Relay dropping out momentarily

  1. #11
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    Was there ever a definitive answer to this? I'm experiencing the same symptom.

    Well, I was - suspecting it might be caused by my power source I hooked up a different 12v supply and accidentally wired it backward... Turns out the FB doesn't like -12v... One loud 'pop' and a few sparks later and I'm looking for a replacement 5v regulator to repair my brain...

    It still works when jumpered to run off USB, but outputs of course are unusable that way. (I'm assuming/hoping that only the regulator blew, and nothing else - nice-sized chunk out of the regulator housing flew across the room, but nothing else appears damaged, apart from my pride)

    Meanwhile I was thinking about ordering a second (semi-defective) brain. It'll probably be a couple weeks before I can get the regulator (waiting for our next order from digikey to avoid paying $$ shipping on a 70-cent part) so that one could substitute without throwing my schedule too far off.

    But I need to know I can conquer the random relay clicks first, else I won't have a use for the second brain.

    j

  2. #12
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    Well it does like 12 volts quite a bit if jumpered for 12 volts. It blew because the supply was hooked up backwards.

    The solution was to replace the brain.
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  3. #13
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    I don't know if the issue's been solved or not... I'm just waiting for my replacement brain to come and we'll see.

  4. #14
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    Quote Originally Posted by PaulF View Post
    Well it does like 12 volts quite a bit if jumpered for 12 volts. It blew because the supply was hooked up backwards.

    The solution was to replace the brain.
    Yes, I was aware of the first part - look again and you'll note that I said "-12v".

    The second point is rather unfortunate for me, as of course my now-damaged brain isn't valid for RMA.

    Thanks (Paulf & ACbusdriver) for the responses. Not what I wanted to hear, of course, but that's life.

    j

  5. #15
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    If the device still enumerates when plugged into a computer and powered off of USB, then the micro is probably ok. Do the LEDs light when you turn the outputs on?

    The regulator is not used with the outputs at all, the voltage is passed through the darlington arrays in the ULN2803 chips. So my guess is you will need to replace both the regulator and both ULN chips on the bottom of the board. I am not sure how the thermal fuse would handle reverse voltage like that, but you could just short that. The fuse is probably what protected the microcontroller though...
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  6. #16
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    Quote Originally Posted by 2k1Toaster View Post
    If the device still enumerates when plugged into a computer and powered off of USB, then the micro is probably ok. Do the LEDs light when you turn the outputs on?

    The regulator is not used with the outputs at all, the voltage is passed through the darlington arrays in the ULN2803 chips. So my guess is you will need to replace both the regulator and both ULN chips on the bottom of the board. I am not sure how the thermal fuse would handle reverse voltage like that, but you could just short that. The fuse is probably what protected the microcontroller though...
    Yes, the LEDs still indicate which outputs are on.

    Question: when set to power via USB and with the 5v regulator blown, would connecting (correctly) 12v still allow proper operation of the relays, if the ULN chips are unharmed?

    j

  7. #17
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    Quote Originally Posted by newkirk View Post
    Yes, the LEDs still indicate which outputs are on.

    Question: when set to power via USB and with the 5v regulator blown, would connecting (correctly) 12v still allow proper operation of the relays, if the ULN chips are unharmed?

    j
    If the ULN chips and the fuse is ok, then yes. Attach +12v and you should see it appear on the output pins. The ULN grounds the opposite pin when the output is "on".
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  8. #18
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    Quote Originally Posted by 2k1Toaster View Post
    If the ULN chips and the fuse is ok, then yes. Attach +12v and you should see it appear on the output pins. The ULN grounds the opposite pin when the output is "on".
    Indeed the relay still works when 12V is applied. Sadly, it still drops out periodically regardless of the new power source (polarity corrected) and still buzzes irritatingly when active.

    j

  9. #19
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    Quote Originally Posted by newkirk View Post
    Indeed the relay still works when 12V is applied. Sadly, it still drops out periodically regardless of the new power source (polarity corrected) and still buzzes irritatingly when active.

    j
    Sounds very much like your power source is the problem. What is it?
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  10. #20
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    Quote Originally Posted by 2k1Toaster View Post
    Sounds very much like your power source is the problem. What is it?
    hmmm. That was my original thought on the matter, which was why I changed to a different power supply. (which was when I encountered my whole reversed-polarity problem)

    First was a 12V 1a wall-wart from a Cisco WAP4410N. (it's using POE now so I had it laying around idle, one of those feather-weight switching power supplies)

    Second was an old 12V 1.2a netgear wallwart, with a hefty half-lb or so transformer inside.

    Later tonight I may be in-dash in the car, if so I'll try to set it up powered by the car battery and see what happens.

    j

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