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Jrk 21v3 ramp up and down request


Hello Pololu,

I am using your wonderful jrk 21v3 to control the motors of a new broadcast pan tilt camera head and would love to be able to
set the ramp down speed as well as the ramp up (max acceleration on the gui) to set a true trapezoidal motion profile.

Are there any plans to add ramp down function (max deceleration) as that would be a great help.

PS: We have already purchased 110 units and will be buying another 100 in a few weeks time.



Understanding Simple Motor Controller acceleration


I’m happy to hear that you (mostly) like the jrk! Unfortunately, we do not have any plans to add deceleration limiting to the jrk firmware–there just isn’t enough room to easily do so. However, we might be able to make you a customized version of the firmware if there are some controller features you can do without. Please contact us directly if you want to discuss this further.

- Ben


Not to be funny, but the acceleration and deceleration ramping is in my opinion a massive part of the functionality of such a controller board. I am desperately trying to create closed loop control for a 3 axis DC gearmotor motion control system. I do not want to use stepper technology for many reasons, mainly being power hungry. I want to integrate the PID functionality of these controllers but really need the ramping feature.

So what are my options here???

I read on a previous post there might be a chance of a customized firmware with this feature.

Please, your help would be greatly appreciated.




The customized firmware with deceleration is available in this thread:

There are two files in that thread; please take note of whether you have a jrk 21v3 or jrk 12v12, and download the correct firmware for that version.

Let us know how it works for you!



Hi David

The Firmware for the ramp up and ramp down on the jrk 21v3 and jrk 12v12 works 100%.

The only problem we have is, that the current setting for the ramp up and ramp down is between 1-600 where setting 1 works perfectly as the speed ramps up and down gradually. But if you use setting 2-600 the motor stops completely dead as it see’s no ramp up or down. Can you perhaps make the ramp up and down longer, so that when setting it between 1-50 it take about 20sec to ramp up or down and 15sec between 51-100 and so on.

This would be extremely help full as it’s a matter of urgency.





The customers we made the custom firmware for were happy with it, so it is unlikely that the deceleration feature is broken. To troubleshoot, we would like to get some more information about your system. Could you post your jrk settings file? You can save your settings file by choosing the “Save settings file…” option within the “File” drop-down menu in the Jrk Configuration Utility. When the motor stops, is the jrk indicating an error in the “Errors” tab of the Jrk Configuration Utility?



Good day

We have managed to get it working. Quite easy after the first attempt.
Another question, I see that you removed the maximum speed setting & replaced it with the deceleration for the board. Is there another way to set the maximum speed limit with the updated software ? (Updated software is with ramp up & ramp down functions)

Kind regards


The custom firmware does not have another way to set the speed limit.