Jrk 21v3 run motor on startup

I just bought a jrk 21v3 motor controller and got it working so far. The only thing is that I actually wanted to use it as servo controller to drive Faulhaber motors at 20 kHz PWM frequency with potentiometer feedback in a standalone application - a gyro stabilized head for filmcameras. But now I found out that I always have to click “run motor” first in the USB configuration utility. Is there a hidden option that runs the motor on startup (power on) without the need to connect the notebook to every controller separately?

Another thing is the jrk 21v3 works quietly due to the 20 kHz and also smoother and more precisely than other controllers I found (without those mirco corrections that are very disturbing when driving a film camera). But it takes a few microseconds before it actually starts to turn the motor. Sometimes the horizon is already off to some degree before the jrk 21v3 is actually starting. Is there an option in the configuration utility that might reduce that delay? The variable Dead Zone in the Pulse Width input field is at zero at the moment.

Thanks a lot in advance,


What input mode are you using and how did you configure the jrk’s errors? If your input mode is Analog or Pulse Width, and you don’t have any errors configured to Enabled & Latched, then the jrk should be ready to drive your motor as soon as you connect motor power and you should not have to press the “Run Motor” button.

The jrk can’t achieve much in a few microseconds (its processor runs at 12 MHz). Maybe you meant milliseconds? If you want a faster response time from the jrk you should change your PID period to 1 ms (default is 10 ms). Then you’ll probably need to reduce the number of analog samples it takes on the Feedback line; just make sure you look at the “PID period exceeded” flag to make sure that the jrk is succeeding in doing a PID loop every millisecond.

This sounds like a very cool project! We’d appreciate hearing more about it when its done.


Thanks a lot, David. Your information was very helpfull. I had some errors configured to Enabled & Latched. Now the motor runs at startup. The delay problem is solved as well. It was due to a low integral coeffcient value limiting the motor response. Will let you know about my progress.

Best Regards,

“a gyro stabilized head for film cameras.”

I think it’s interesting how we come up with cool ideas that can make life easier. To give you an idea, I obtained a three wheeler (for disabled transport) that had a bad controller, and a push mower. I removed all 4 wheels on the mower, installed the rear axle (24V) and cut the front wheel off the the three wheeler. I made a large servo using this jrk 21v3 on a “wheel drive motor” for a “Barbie car” for the steering. So now I cut my grass by remote control. I’ve been thinking of attaching a coil to the flywheel (coil + spinning magnet = voltage) to charge the 12V battery that runs everything so I don’t have to put it on charge when I’m done cutting the grass. I must say it works GREAT!

It’s been a few months, I’m ready to see some pics of this cool sounding camera stabilizing creation.

Hello, CavemanCarl,

Your remote controlled lawnmower sounds like a really neat project too! I’m sure lots of people would be interested if you share some more about it and show a few pictures.

- Kevin

CavemanCarl, I split your most recent post into its own thread in the “Share Your Projects” section.