Can you make the Jrk work like the Trex Jr?

I am wondering if it is possible to use the Jrk as a speed controller where the external input (like the analog voltage) can be used to set the speed like can be done on the Trex Jr. I know that you can make the Jrk work in speed control mode through the serial commands by setting it to none for feedback and then changing the max duty cycle. But I did not see a way to do this using input signals.

Is it possible or do I have to use a Trex Jr if I want to do this ?


Hello again, Dwight -
Yes, the jrk can do speed control via an analog input. If you set Input mode to Analog Voltage on the input tab of the configuration utility, and operate in no-feedback (speed controller) mode, the analog input will be converted using the input scaling parameters into a “target” value which is interpreted directly as a speed control command, instead of going into the PID calculation. You will want to adjust the input scaling parameters so that the min and max values reached by your potentiometer scale to target values of +600 and -600, which is the full scale of the jrk in speed-control mode.

Parabolic scaling, an asymmetric center pointer, and an input dead zone are all available using the input scaling parameters, so the jrk should be usable for a wide variety of setups.


This is great to know. I can generate an analog voltage from a DAC so that is an alternative approach for me to control the Jrk if the direct via USB is problematic for me. I find this easier than replicating the RC signal pulse on a digital out line.

BTW, was this described in the documentation and I just missed it ? If so, could you tell me what page ?



The input modes are described in section 3.b.. If you’re using a programmable digital main controller, I strongly recommend using the serial interface since the analog and RC pulse interfaces are not digital and therefore are more susceptible to noise.

- Jan

My other post is about interacting with the Jrk via the USB which is my preferred approach. As I mentioned, the analog approach is a fall back. I am waiting to see the C code mentioned in the other thread to try the direct control approach