Generic Linear Actuator with Feedback and Pololu jrk 21v3

using Generic Linear Actuator with Feedback and Pololu jrk 21v3


ok so i plugged it all in as per specs. loaded file from configuration page (jrk21v3_linear_actuator_settings.txt)
this sets the pid’s to
35 / 0 / 60
Period 10ms
and integral 1000

the feedback settings are
abs max 3925
max 3756
min 80
abs min 40

input is serial usb … i’m using the slide bar to set target from 0 to 4000 ( should be scaled from the feedback settings right ? )

if i full extend… i have to press stop motor as it still trying to push the rod… extend… i see target 3896 and scaled feedback 3247
if i put 0 and set target, i get the retraction …target 0 , scaled FB 1078

the yellow light flashes and i need to click stop motor etc… most the times the configuration util crashes and i need to restart and connect and stop motor.

ok so i figure feedback is bad from settings,

i apply the values i found on the top target:scaled FB readings and put in feedback tab then apply settings to device

Absolute max 3247
max 3240
min 1078
abs min 40

i click the tab at 0 and set target works.
i click max of 4000 and target and works…

is this the way to do this ?

also how can i speed things up ?
i’m running a 12V 3.3 AMP PS
but not sure on how to play with pids ?

also is it normal that this shaft is so noisy ? also blackish on the rod .
Can we grease this or lub it ?


Does the jrk report any errors? The error code can be found in the “Errors” tab in the Jrk Configuration Utility.

The absolute max and min values for feedback should not need to be changed. The linear actuator has built in limit switches that will prevent it from going beyond its range of motion, so setting a target beyond its limit will not break the linear actuator. Changing the max and min feedback parameters, as you have already done, should help.

The maximum speed of that linear actuator is 1.5 in/s and it is not possible to go faster at 12V. These linear actuators tend to be noisy, but I do not know how loud your actuator is. Also, I would not recommend applying grease or lube on the actuator, as it comes pregreased. Could you post a photo of the “blackish” thing you describe?

- Jeremy

here you go

ill build en enclosure, for the sound problem,

But the fact the yellow light stays steady yellow tells me it’s still trying to continue the movement, therefore the feedback is not getting read right, (no errors)

i need to use config util , click stop motor and then the light flashes (awaits command)

so definitely something wrong.

you want to logmein to my dev box to see ? Give me a number to call you at and we can try that.

That “blackish” stuff on the rod is grease from the manufacturing process and wiping it off should not affect the performance of the linear actuator.

It is ok for the jrk to continue to try moving the linear actuator. The limit switch will prevent it from damage and will ensure that it has reached the end.

Alternatively, you could send a smaller range of target values or adjust the feedback scaling parameters so that the system can reach all values between 0 and 4095.

- Jeremy

problem is i can’t send new command while it’s moving, it crashes the config util and need to un/re plug usb to get it working again.

Feedback was adjusted but still does it for a reason i ignore, will try more

It sounds like when the actuator hits its limit switch, it causes trouble with the USB connection between the jrk and the computer. Is that right? I recommend decreasing the Maximum Feedback and increasing the Minimum Feedback so that the actuator never hits the limit switches. If you do that, does the utility still crash?

- Jeremy