Quote:
Originally Posted by J57ltr
So it was a new or pretty new servo in your case? I am wondering why adding a cap "fixed" Joe's problem.
Jeff
|
WARNING: Long boring technical explanation follows:
We've seen the same thing on the bench since this problem was reported. Apparently, some of the JR servos draw peaks (short -term) of several (5-6) amps for a couple milliseconds when changing direction. (We have speculated that the drive transistors in the servo are shooting-through during direction changes, but haven't yet verified that.) It's just barely long enough of a surge to trip the BEC over-current protection in the MMPro, and it shuts off the BEC for about 50ms. Adding a big capacitor to a servo connector (like a stutter-stopper) supplies enough current during those big surges to keep the MMPro from tripping the over-current on the BEC.
We are bench testing a hardware change that will add a very slight delay to the over-current shutdown on the MMPro to compensate for the JR servos.
Note that we have only seen this behavior on two specific JR servos, and adding some capacitance to the BEC line seems to be a good fix for the issue.
Patrick