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View Full Version : How to fix ground plane voltage differences which cause the prop chip to reset?



Kye
03-25-2012, 04:43 AM
So, the issue is simple:

When I plug a TV into an RCA jack I soldered onto my proto-board the Prop Chip resets. I think this is due to the ground planes being different. I don't really know a good solution to think problem. Not all TV's I plug the prop chip into cause the prop chip to reset.

Any suggestions? More capacitors near the prop chip? I have 1 uF ceramics on the 4 power lines and 0.1 uF on 2 of the 4 power lines. Should I put some 10 uF caps near by?

Thanks,

Mike Green
03-25-2012, 04:52 AM
If there's that much difference in the ground voltage or that much noise on the TV's ground, I'd avoid using it if possible.

Leon
03-25-2012, 06:46 AM
Try unplugging the TV before connecting it to the board.

evanh
03-25-2012, 06:56 AM
What sort of "proto-board" are we dealing with? Is it home-brew? If it has a decent spread of ground plane and some ceramic caps to Vdd then you're pretty set there.

Try measuring the AC voltage of the TV aerial of the offending TV with an ordinary multimeter while it is turned on. Or measure the composite plug itself. Measure from an earth. You might find there is floating AC volts there, enough to give a tickle.

Likewise, measure the Prop board ground for AC volts. Again, with respect to an earth.

There is protections but everything costs. If you can eliminate the noise source instead then that's cheaper.

jmg
03-25-2012, 07:04 AM
... I don't really know a good solution to think problem. Not all TV's I plug the prop chip into cause the prop chip to reset.


Most TV's skip any ground wire, but they have substantial capacitance leakages via the mains SPMS,
If you have a real earth at the other end of your Prob board, you will get spikes on the PCB inductance.
Solutions are to lower the spikes, or the dV/dT or lower the common mode inductance.

If you can power your Prop from a low-leakage, insulated power pack, and avoid hard grounding, then you will lower the spike energy.

If you have a PC which is earthed plugged into the board, and you want to avoid resets in this setup, then
you can run a separate lead to any unused socket on the TV, so there is no charge build up

or, giving the discharge current a path that does not include any Prop-shared traces is another option.
ie the RCA socket is moved to be right against the USB connector.