Experience the same, one or two servos work. Adding more and I see issues which look power related, jittering.
On Tuesday, 17 December 2019 22:50:19 UTC, [email protected] wrote: > > I'm using a TowerPro SG90 Micro Servo and having trouble getting it > powered through the Beaglebone Blue. I apologize for the wall of text, but > i've tried quite a bit before coming here and want to make sure you all get > everything I've found. I also apologize for the lack of pictures, i didn't > photo-document things, but I have tested everything multiple times. > > *Problem: When attempting to drive servo(s) from BBB's powered servo > rail, servo(s) just click and don't move at all.* > > SG90 info: > Signal 50Hz > V+ : 4.8-6V > > Connected to BBB by USB cable. Connected 14.4V (up to 60 Amp) power > supply to DC in. > Tested Items: > > 1) When no servo's are attached, powered rail is 6V (TRUE) > 2) When no servo's are attached, signal rail has 50Hz (TRUE) > > Add servo to setup > > 3) Signal rail is still 50Hz (TRUE) > 4) Powered rail is still 6V... > 4A) At (normalized) pulse of 0 (TRUE) > 4B) At any other pulse width (FALSE) it varies between 1.2V and 5V > > At this point the Voltage rail is fluctuating wildly. I decided to check > if there was an induced signal in the voltage rail. > > 5) Frequency on Voltage Rail at ALL non-zero (normalized) pulse widths is > 4Hz > > So i decide maybe the servo is bad. > > 6) All above results duplicated across 3 known good servos > > So, lets try pulling power from somewhere else. > > Using a 5V bench power supply with SEPARATED ground from BBB > BBB Signal - signal in > Bench 5V Power - V+ > Bench Ground - V- > > Yes, bad design. Should use BBB Ground, or tie BBB ground to bench > ground... but > > 7) Servo runs as intended. > 8A) Check V+ for induced signal (None found) > 8B) Check V+ for voltage variation under load (none found, always 5.2V) > 8C) I'm unable to measure the current with my setup, however specs say > 550mA for this servo. > > So... Now we fix some things up. > With Bench supply 14.4 V to BBB DC in this scenario the 5V is achieved by > a DC-DC converter (10-15)V - 5V. So the ground is ultimately shared by all > connected electronics. > > 9) Repeat all test with same results. > > Am I missing something? Does my BBB have a bad power supply for the Servo > Rail? What else can I try? Software used to test this is the Robotics' > Cape test software > http://strawsondesign.com/docs/librobotcontrol/rc_test_servos_8c-example.html > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/79fa8c17-a6af-4304-842d-f5af4288fe3eo%40googlegroups.com.
