Author Topic: PCB Short That I Cannot Seem to Locate. A Challenge For All Electrical Engineers  (Read 1454 times)

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Offline MastermimeTopic starter

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Hello everyone,

For my project, I'm making a thermoelectric bracelet for body temperature regulation (essentially a personal air conditioner) and I've been having an issue with printed circuit board. Usually, its pretty easy for me to locate the shorts, but this one is perplexing.  As you can see in the schematic, this board is controlled by a Sparkfun Pro Micro. I'll consider that along with the RGBs section 1 of the circuit and that is working just fine. 

The problem is section 2 (or so I think) and that's the circuitry responsible for stepping up the voltage and applying the correct polarity (using H-bridges).

When I dont have the boost chip soldered in, power is applied to the microcontroller and section 1 works just fine.  However I do notice there is a short between power and ground on the boost converter chip's pads. So its like 1 part of the board is shorted and the other is working just fine.

When the chip is soldered in, both sections ceases to function and my multimeter shows there is continuity between + and - throughout the board.

If someone could shed some light on this problem, I would be very greatful. This one has truly stumped me so if one of you can locate this, then you have earned my highest respect and gratitutde

Offline Billy

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I didn't look at the schematic closely, but are you positive the chip isn't shorted?
Have you tried a second chip? Stranger things have happened.

It's also possible that the power supply simply has too high of impedance and the TEC has too low.

Offline MastermimeTopic starter

  • Supreme Robot
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Hey Billy,

Thanks for the response. I was able to locate the short yesterday. If you look at the H-bridge section of the circuitry that drives the thermoelectric cooler, I accidentally connected the resistors from the gate on the top two transistors to the positive line instead of ground so its actually creating a direct path from 10v to ground which is causing the short. These resistors are intended to pull the gate LOW when no signal is being sent to the gate, but they are currently in a pullup configuration, which is wrong.

Will never do that again

 


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