EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: FIFO on June 08, 2012, 08:20:16 pm
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I'm running power and serial communication through a really long cat6 cable. When powered using my bench power supply, everything works great, but when I switch to a 12v battery, communication(over serial) starts erroring out pretty badly. I'm just looking for general advice on what to look for, or ways to increase the signal quality.
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Do you have a ground connection through the CAT-5 cable? If not, the ground connection may be being made via the power supply.
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Originally, I did not use the ground pin on the serial connection. This was no problem with the bench top supply, but as soon as I moved to a battery, communication broke down. I then tried shorting the ground pin to the negative side of the battery, and this did not work either. Then, I connected one of the wires in the cat6 from the circuit to the ground pin, and all was well again.
Now, keep in mind, 1 wire is positive, one wire is negative, and now a third wire is from the negative side of the far end of the circuit. Why this works, I didn't understand.
So now I switched to battery, and things are still working, great. THEN I connected the actual pc to the battery, and everything broke down. ALSO, I connected the device to another pc and the serial communication would not work either. So the real problem comes from connecting that original pc to the battery. I'm assuming it 'dirties up' the power or ground somehow? How can I test for the problem, protect from it, etc?