I want to drive jrk 21v3 with the analog input.
The power supply is 15v. I connected the Rx pin and ground pin to my analog input source.(0~5v)
I also used the “learn” button in the input tab of Pololu UI to calibrate.
However, the output to the motor is not linear( input 0~5v should have output -15~15v)
The output has a large deadzone at the input from 3.3~1.7 and the linear range is also narrow.
Is my setup wrong?
How are you determining that the output is not linear? Are you measuring the voltage across the motor terminals on the jrk, or are you looking at the motor’s speed? Is the motor connected, and if so, is there a load on the motor? Could you also post your jrk setting file, so I can take a look for anything that might be causing the behavior you are observing?
I measured the voltage cross the motor and there is no load to the motor.
Even I remove the motor and measure the voltage(motor outputs, A and B)
It is still not linear. analog input signal through Rx is form 0~5V
The following is my motor setting.
From looking at your settings, I noticed your feedback mode is set to “None”. When the feedback mode is set to “None”, a target of 2648 corresponds to full speed forward (likewise a target of 1448 corresponds to full speed reverse). More information about this can be found in the “Feedback Options” section of the jrk user’s guide. This also means that with these settings, any target set above 2648 will result in a duty cycle of 100% (and any target below 1448 will result in a reverse duty cycle of 100%). Changing the target maximum and minimum values in the “Scaling” section of the input tab to 2648 and 1448 respectively, should allow you to use the full analog input range of 0 to 5V.
With the motor disconnected, do you still see non-linear behavior or a dead zone near the neutral point? If so, could you send some screen captures of the plots from the jrk configuration utility that demonstrate the behavior (The plots can be accessed by clicking on the small graph in the top right hand corner of the Jrk Configuration Utility.)?
Thanks for the help. The new setting works.
And there is no nonlinear region near the dead-zone, when I disconnected the motor.