Issue with feedback loop of multiple Jrks (21v3)


We are trying to run multiple jrks (10) simultaneously. I connect two of them via USB to computer. The RX input is the sin waves from NI DAQ assistant.

The position sensor encoder with analogue output is used for the feedback loop. One Jrk woks just fine with feedback loop, but whenever i include another

Jrk the feedback signal becomes so noisy. I switched the devices around to diagnose the issue, but I have had no success so far. I attached the disturbed signal

for the reference.

I really appreciate if you could help me diagnose the issue. Another question is if have had any experiences with multiple Jrks with position feedback loop, and

What is the best way of setting up the system? USB, Daisy chaining, or any suggestion you might have…

Some updates:

I added two more jrks to the system (4 total). The two new one seem to be working ok, but i still get noisy signals from the second one. Is it something to do with the second channel? I switched USBs, but still have issues with the second one…


I am sorry you are having problems with your jrks. Could you tell me more about your setup? What are you driving with the jrks? Could you post some pictures and a diagram showing how your system is connected? Could you also post the jrk settings file?

In general, if you are trying to control multiple jrks I suggest you daisy chain the jrks together. You can find more information in the daisy-chaining section of the jrk user’s guide.

- Jeremy


“What are you driving with the jrks?”

Ten of these motors:

“Could you post some pictures and a diagram showing how your system is connected?”


“Could you also post the jrk settings file?”


Last update: only channel # 1 and channel # 10 is working (corresponding to files #1 and #10), but other channels have same issues that i mentioned earlier. I’ll post the settings file with other message.


Settings file.
3.txt (1.38 KB)
2.txt (1.38 KB)
1.txt (1.38 KB)

Setting files.
10.txt (1.38 KB)
9.txt (1.38 KB)
8.txt (1.38 KB)

I suspect something in your system is wired incorrectly and causing that square wave to be put on the FB pin of the jrks. If you have an oscilloscope, you could verify this by probing the FB pin. I recommend carefully inspecting all the connections you have made to the FB pin of the affected jrks, and making sure nothing has been shorted to it. It is hard to tell from your photos how everything is connected. Could you post a schematic of how everything is wired? You mentioned in the beginning that you thought only the second jrk was causing the issue. Could you remove it from your system and see if any of the other jrks are affected? Also, I think it would be better to troubleshoot the problem with fewer motors. Could you simplify the system to only two motors and see if you can get them to work? Lastly, if you have access to an oscilloscope, could you measure the AUX pin and see what it is doing?

- Jeremy