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Topic: Works with 2 power sources, but not 1... (Read 1 time) previous topic - next topic

Pablo C Elias

Hi, about those tieing grounds issue.. What about possible potential difference between grounds? Is that an issue? How to solve that? wouldnt different ground potentials change voltage levels (ex: a regular +5V change to +7V if the reference ground got +2V due to potential diferences.) Since boards are not really earth grounded, isnt that a problem?


James C4S

it was strange that the board was working when there was no power attached, but the driver was being powered - "where is this power coming from??"

If you do a Google search for "AVR back-powering" you'll see this is a common issue with the ATmega.  Another case that gets people is when they try to use the Analog Inputs to measure a battery's voltage.  If the battery is connected directly to the pin, it will "back-power" the chip.
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wow, super intresting, and  i would have gotten really stuck on this sometime down the road - thanks for the follow-up.


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