JRK21v3 Motor Output Voltage

Hi all,

I’m new to this forum, and the JRK motor controllers. But I’m a electrician and instrument technician by trade, so I understand this stuff pretty well. I’m just a bit confused with the JRK output.

I have recently purchased a JRK21v3, which I am using to control a 12VDC wiper motor as a servo.

I have connected a 5K pot to the feedback pin, and another 5K pot as an input controller and all seems to be working well. I can control the Setpoint and Process Value with the pots, scale the feedback, drive the motor forward and reverse etc etc.

My question is, why are my Motor output pins only putting out around 4V, even though my supply voltage to the JRK is 11.1V

To my understanding, the JRK has a 5V regulator built in for the system to function, but am I wrong in assuming that the motor output should be equal to the supply voltage?

My 12v wiper motor connected across Motor A and B is working, but it’s moving very slow and lacking the power it has when connected directly to 12VDC.

When I disconnect the motor and measure the terminal voltage, (when the set point and feedback are different, so it’s trying to drive the motor, of course) I’m only getting around 4v.

How can I get a full 11.1v out of my motor terminals?



Hello, Cory.

I am sorry you are having problems with your jrk 21v3. The motor outputs from the jrk should be a PWM signal from 0V to VIN. There are several things that could be causing the behavior your are describing. You might start by checking the “Max. duty cycle” setting under the “Motor” tab of the Jrk Configuration utility to see if it is limiting the duty cycle (e.g. if it is set to something less than 600).

If that does not fix the problem, could you try disconnecting your motor, setting the jrk’s feedback mode to “None”, setting the input mode to “Serial”, and setting the target to something greater than 2648 using the slider in the “Input” tab? Please note that if you are using the slider, you will need to click the “Set Target” button or enable the “Automatically set target” option for this change to take place. You can monitor the duty cycle output using the plot in the upper right-hand corner of the Jrk Configuration Utility. Clicking on it will open a larger version that allows you to select what data to show. If you get close to the full VIN voltage when doing this test, it is likely that either your scaling options are not set correctly, or your PID coefficients are not tuned.

If the scaling settings in the “Input” and “Feedback” tabs are not scaled properly, your conditions for getting a 100% duty cycle output might be impossible to reach. I recommend using the “Learn…” button for setting the scaling values. While using feedback, the PID coefficients are used to determine the duty cycle. Some tips for tuning the PID coefficients can be found in the “Setting Up Your System” section of the jrk controller’s user’s guide.