Electrostatic Discharge (ESD) and uSSC

How much should I worry about ESD for the uSSC? Do I need a grounding strap when handling this thing? ( I ask because I’m getting some strange behavior and I want to rule out the pololu board --and because if the pololu board IS suspect, we need to order another one today! )
(Needless to say, I have been handling this thing without regard to ESD…)



We haven’t seen many ESD-related problems here, and we can definitely get a lot of sparks here in Las Vegas. We generally try to be as rough on designs as possible during development so that we find out if they are overly sensitive, but we do generally take basic precautions (like at least discharging ourselves on some nearby object) out of habit.

What is the strange behavior you are seeing? Have you gotten some noticeable zaps when touching the uSSC?

- Jan

Seeing as you’re relatively rough on the chips, I’m not worried… No detectable sparks from touching it. Once I was probing the servo-power pins and I saw a spark between the voltage probes. Would that matter? It’s been reliable with our test servo. I believe we may have a ground problem – the pololu board is used for it’s signals, not power.

We have the pololu uSSC commanding parallax HB-25 motor controllers. It was late last night when we were debugging this, and I can’t remember if we have the pololu servo-ground plugged in. (HW is at home…) If not, then the signal line could be floating. Still, here are our symptoms: The motor controllers don’t seem to respond on all pololu slots-- and when they do individually, when we plug in more than one, the first one stops working.

Thanks for your response.


When plugging in multiple servos or other devices changes their behavior, it’s usually a power or noise problem. One thing to look for on the servo controller is if it resets. You would then see just the yellow LED on as if it had just powered up. Otherwise, I doubt it’s a problem on the servo controller side. Do you have some regular servos you can try instead of the motor controllers?

- Jan

Yes, we have a test servo that we developed the prototype code with. That’s why I said the uSSC has been pretty reliable. We have little green light flashing at the interval we expect, and the uSSC board resets properly. So I really think that the problem is the possibly floating signal to the motor controllers. I really wish I could go home and test it… but I gotta wait till 5pm.

Thanks again.