Voltage suddenly dropping from 9V to ~.2V. Why?

Discussion in 'The Projects Forum' started by z0oinks, May 1, 2015.

  1. z0oinks

    Thread Starter Member

    Sep 12, 2012
    129
    0
    Hey guys,
    I'm building an inductive charger using Adafruit's Inductive Charging set (link below) to charge my Astro A50's. I've got it set up so that the 9V DC plug goes to a set of alligator clips which then connect a NO momentary switch, which then connects to the inductive transmitter. Last night everything was working fine, but today something went wrong. When I connect the pair of alligator clips and test the connection right with the momentary switch open there using a voltimeter, the voltage reads 9V. Then if I close the switch, the voltage drops to 0V, but spikes every couple of seconds to somewhere between .1V and .3V. Also, the headphones will power on from the current being sent to them, but apparently it isn't enough to keep charging it after that.

    I can't for the life of me figure out whats making this happen. All wires are connected to the correct polarity, there aren't any shorts as far as I can tell, and I don't know what else it would be. As I said, everything was working perfectly fine last night. Does anyone have any ideas?

    Link to inductive charger: http://www.adafruit.com/products/1407
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,771
    1,103
    What are you using as the 9V supply?
     
    #12 likes this.
  3. z0oinks

    Thread Starter Member

    Sep 12, 2012
    129
    0
  4. #12

    Expert

    Nov 30, 2010
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    You should find out whether the power supply works with other things that need 9 volts. If it does, the wireless transfer device might be bad.
     
  5. z0oinks

    Thread Starter Member

    Sep 12, 2012
    129
    0
    I don't have anything else to see if this works with :/

    I was originally using a different 9V adapter and that was giving me the same issue, which is what caused me to buy another (and then the adapter by itself was giving a reading of like 3V with nothing attached, so I think it just shit out on me). I believe my last adapter was unregulated, but I'm pretty sure it would read 9V when the circuit was complete. Could that have caused some damage anyway?
     
  6. #12

    Expert

    Nov 30, 2010
    16,252
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    Unregulated adapter that loaded down to the proper voltage...probably not the cause.
    Did you see anything that tells how much current the transmitter needs? I looked, but that website was not easy to read and I had somebody here in my real life trying to get me to leave.

    Oops. Here is the description on your web page selling these:

    "We don't have any datasheets or specifications for them."
     
    Last edited: May 1, 2015
  7. z0oinks

    Thread Starter Member

    Sep 12, 2012
    129
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    Alright, that's a relief at least.
    The name of the product details it as "5v @ 500mA Max", and the power supply they use in one of their guides for the charger uses a 9VDC 1000mA adapter
     
  8. #12

    Expert

    Nov 30, 2010
    16,252
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    It seems you followed the instructions, and it still failed. I don't know what to do next. Measure the current that the transmitter uses? But you need a power supply that works to measure the current. Broke two power supplies? Maybe the transmitter is shorting out.

    It's all down to, "maybes" from my point of view right now. This is where I growl and take it to my workbench. It's so much easier with a thousand dollars worth of test equipment. :D
     
  9. z0oinks

    Thread Starter Member

    Sep 12, 2012
    129
    0
    I wish I had expensive stuff like that :p
    Actually, looking at the transmitter's board, there are some burn marks around the micro-controller. So something went wrong somewhere....
     
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