about current surge on PSCU
KelvinL
Posts: 15
Hi there,
Finally I've done makeing the servo move on PSCU(Propeller Servo Controller USB).
Using PSCU to control over 150 servo move simultaneously is quite convenient without taking too much effort to layout my own servo controller.
I think PSCU has it's advantage that i can fix the firmware to the communication protocol I want, and it's quite simple.
But I still got a problem and wish to have any idea comming from forum to help me.
I found that servo get jammed and trembled once they didn't get enough current, and then it keep demanding high current even when i switch servo power off and on again.
This happend especially when i just switched servo power on.
I watched from my Amp meter and see it showed the sudden current is over 5A when having all 16 servo attached but without load (yes, the servo itself has friction lost on moving even we don't attach any object to it).
I swtiched to a more powerful power supply(5v 40A) , but not solving it.
I also found that servo control use the previous "Parallax Servo Controller(which use sx chip)" will giggle at the same situation , but it won't sustain and will quick revive to demand
position.
I realized they won't perform the same , and i know the key issue is current. I tried to study into the servo ramping code but it's still too dificult to me.
I think a big capacity at the power could help a little, but is there any better way to provide enough current at servos' sudden need?
and maybe the start up sequence of PSCU could be changed to avoid this problem, but how?
thanks if you may do any suggestion to me.
Finally I've done makeing the servo move on PSCU(Propeller Servo Controller USB).
Using PSCU to control over 150 servo move simultaneously is quite convenient without taking too much effort to layout my own servo controller.
I think PSCU has it's advantage that i can fix the firmware to the communication protocol I want, and it's quite simple.
But I still got a problem and wish to have any idea comming from forum to help me.
I found that servo get jammed and trembled once they didn't get enough current, and then it keep demanding high current even when i switch servo power off and on again.
This happend especially when i just switched servo power on.
I watched from my Amp meter and see it showed the sudden current is over 5A when having all 16 servo attached but without load (yes, the servo itself has friction lost on moving even we don't attach any object to it).
I swtiched to a more powerful power supply(5v 40A) , but not solving it.
I also found that servo control use the previous "Parallax Servo Controller(which use sx chip)" will giggle at the same situation , but it won't sustain and will quick revive to demand
position.
I realized they won't perform the same , and i know the key issue is current. I tried to study into the servo ramping code but it's still too dificult to me.
I think a big capacity at the power could help a little, but is there any better way to provide enough current at servos' sudden need?
and maybe the start up sequence of PSCU could be changed to avoid this problem, but how?
thanks if you may do any suggestion to me.
Comments
You might not want to be telling all of your servos to move somewhere just when things first turn on. (Especially at program start, to not tell every servo to go somewhere immediately, put some delays in there, sequence or offset things a little).
If your program isn't telling everything to go to a position at the same time, and it's merely a problem caused by giving them power, you might need to power on banks of servos sequentially (groups of 4).
Finally, you'll need to determine if your inrush problem is due to all of the capacitors of the servos, or lack of capacitance near your power supply. When dealing with motors, currents that high are expected. That's why we have capacitors, but that initial charging of all the capacitors can be a killer, too. You might need a soft-start power supply, or some inductors.