Is there a risk of spikes/surges coming to my PC through the USB?

Hi all --

I have a fairly standard smartcar robot using a standard H-bridge and two motors... and the smartcar has a 4-pack of AA NiCad batteries... and of course I program it through the USB to my laptop.

Currently, when I plug it in to my laptop, it springs to noisy action, because the USB voltage powers it, and I haven't built any on/off aspect that would block that.

My question is: Since I'm plugging this mechanical, voltage, motors beast into my USB ... is there any risk that at some point spikes or surges could go through the USB and zap my computer a bit?

If yes, what are the typical ways of protecting that? Having a way of conveniently disconnecting the H-bridge before I connect the USB, or something?

thanks!
eric

Computers (or at least the USB connections) can certainly be destroyed by surges and shorts in USB lines. Have you heard of the USB Killer?

It is a good idea to put a toggle switch between the battery supply on your robot and the H-bridge, so you can turn off the motors while programming or testing other circuitry. Better yet, make the switched motor power completely independent of the robot MCU power (connecting the grounds, of course).

After a mishap, where the uController project sent a higher voltage into my computer through the USB port, I use powered USB hubs between the computer and the uController.

thanks to both of you guys –

eric