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By anthonytw
#147384
Hey everyone, I have a question I'm not entirely sure about.

I'm using (or working on using) a Beaglebone to drive some DC motors. For ease of prototyping, I purchased a motor driver BOB here (http://www.sparkfun.com/products/9457). The ARM on the Beaglebone will provide the small signal supply voltage (Vcc) and a wall-wart + hackjob regulator circuit will provide the motor supply (VM1/2/3). However, I noticed (perhaps too late) that the BOB shorts the small signal ground with the power ground. Normally the grounds should be the same but in this case the Beaglebone is being powered via a USB cable connected to my computer, whose ground I'm not sure I can safely short to my motor supply ground. Is there a safe way to configure this without having to build a common power supply for both systems to run on?
By Duane Degn
#147436
I'm pretty sure it's normal to have signal and power grounds connected together at some point. I believe it's best practice to have this connection at only one location.

Many motor driving circuits will not work without some sort of common ground connection. I really don't think this will hurt your cmputer, but it's often a good idea use a powered hub in cases like this so the hub get any abuse before the computer does.