Position control with the JRK 12v12

i’m trying to use JRK 12v12 to provide position, direction, and speed control of a ServoCity actuator (robotshop.com/en/electronic- … meter.html) to control the system. i’m also trying to operate the system within a user defined range of the manual potentiometer so that the actuator is either fully extended or fully retracted when the potentiometer reaches the ends of the user defined range with position control as the pot is rotated thru the range. the best I can do is… the actuator will only move to fully extended when you reach the upper end of manual pot’s defined range and fully retracted when the manual pot approaches the lower end of the defined ranch. I have no position control in between those two points. HELP???/


I am sorry you are having trouble getting your linear actuator to work with the jrk. It might be that your input scaling parameters are not set to get the results you want. Can you post your settings file? Also, can you check with a multimeter that you are getting the full range of analog voltages on your control potentiometer and the actuator’s feedback potentiometer?


I set everything back to default. I also had another problem…after a period of time it started giving the error “max current exceeded” the only way I could avoid this was to set the max current to 0 (no limit). i think it started when i tried to work with the coefficients under the PID tab. I am very inexperienced with this stuff, so I kinda need you to be very specific if possible.

I tried giving you some specific things you could do to start troubleshooting, but it is hard to tell from your reply if you tried them or even if you resolved your initial issue by going back to the default settings. When you ignore all of my feedback, do something entirely different, and bring up a new question, it makes it difficult for me to understand your setup and help you with your problem.

Under the “Using a jrk motor controller with a linear actuator with feedback” section of the product pages of our linear actuators with feedback (for example, this linear actuator page), we have written a set of instructions and provided a link to a jrk settings file, which could be used to help you get started. Can you download that jrk settings file, follow the steps, and see if that works?

If that does not work, can you specifically explain what is not working? It would be useful to know what you expect your system to do, what it is actually doing, and all of the steps you took in setting up your system.


SORRY! I didn’t ignore your feedback! it was my assumption that if I didn’t include it in my response that it would be taken as it was ok and we would move on. that’s my bad. I didn’t ignore you and do something different, I set it back to default when I couldn’t get it to work (before I posted here). the “current exceeded” issue was simply an issue that I accidentally omitted in my original posting. if my posting asking you to be specific in someway offended you (based on your post it seems like it did) it was not my intent. I was just pointing out that my knowledge of this stuff and most of the terms are very new to me and I don’t want to waste time asking “what’s that”. ok on to the important stuff… the analog voltages are fine with the potentiometers. I know nothing about scaling. I cannot post any settings because I set everything back to default and I do not remember them all. I tried several different set ups. In the users manual link from the place that I bought the JRK at there is no section for setup using a linear actuator with feedback. so I didn’t know that download existed. in any case, I downloaded it to the JRK. I noticed that the program sets the input to “serial” am I correct assuming that means I can use the computer to control the system? I will post again when I get a moment to try it. thanks

ok, I downloaded the file. when I run the JRK with the input set to “serial” and tag “set target” the actuator moves to that position and starts clicking. the clicking is very hard to describe. then the JRK starts to get hot. I changed the input to analog and hooked up the manual pot. the actuator wouldn’t move at all when turning the pot. the manual pot is connected to the RX pin as well as the GRD pin and a 5v positive pin. the actuator is hooked to the FB pin as well as the AUX pin and a GRD pin (as displayed on the link you provided). aside from trying the analog input all settings are as downloaded in that file. there are no errors under the “error tab”. I am lost!!!

It sounds the linear actuator is continually trying to reach its target position, but overshooting its target repeatedly and reversing direction because of the PID parameters in that settings file, which are tuned for the linear actuators we carry (they move slower than the one you are using). The jrk is likely getting hot because it is continually reversing the polarity of the power supplied to the actuator. To get better performance, you should try tuning the PID constants for your system. If you are not sure how to do this, you might consider reading the “Tuning the PID constants” section of the jrk’s user’s guide, which can be found under the Resources tab of its product page.

As for when you try to control the linear actuator with a potentiometer, have you clicked the “Apply settings to device” button in the bottom right of the Jrk Configuration Utility? If you have tried clicking that button, but analog input control is still not working for you, can you save your settings file and post it here so I can check your settings? You can generate this file by clicking File > Save settings file.


thanks for explaining the clicking and heating up issues. I was afraid something was shorting out, but I couldn’t find it. I read section 3.d. “PID Options” of the owners manual and honestly understood very little. I mean I get how it’s calculated, but I don’t know where to get the figures. it’s not completely clear to me what the coefficients are for and what function they have. I can just plug #'s in but what happens if the integral coef. is higher than the derivative coef… I have no idea where they should be set to accomplish what I need.

I will post the settings on here…not a problem. i’m 100% sure I tagged the “apply settings to device” button. keep in mind that downloaded file came up with a serial input. the only thing I changed was changing the input to analog.

Having a large integral term can lead to overshoot and instability. To get a better understanding of how PID control actually works, you can read this Wikipedia article.

The input mode in that settings file is, by default, set to serial. It does not sound like you changed much, but if you post your settings file, I can double check to see if I notice anything obviously wrong. Can you also post a picture that clearly shows all of your connections?


ok, I got the actuator to move with the manual pot. the pot has a 300 deg. range. it takes all 300 degrees to move the actuator 1". it moves slowly with a lot of the “clicking” and the JRK getting really hot. I’ve uploaded my current settings for you to look at, and hopefully tell me what’s happening. Please let me know if I didn’t get it uploaded correctly. Thanks
stang.txt (1.39 KB)

As I mentioned before, the controller getting hot is likely because it is switching on and off to move towards its target position, so you could probably better tune your PID constants to adjust for that.

I tested your jrk settings file with one of our linear actuators and a 10k pot; it works fine for me. You might try using the “Learn…” button to scale the input ranges for your potentiometer. You can also manually edit those values. You can learn more about those features under the “Input Options” section of the jrk’s user’s guide.


I remember the post about the getting hot problem and needing to work on the PID to fix it. Problem is I’ve read all the info. and I’m missing something. I have know idea what each coefficient does or what changing each one would cause. Do you have any suggestions to get me started? I know the input stuff. I need to get the heating up fixed 1st. It overheats to fast to get the input taken care of. Thanx

Besides that Wikipedia article and the section in the user’s guide about PID tuning, I do not have any additional resources to recommend that might help you. But there should be plenty of resources out there.