Hi All,
Have a serious time crunch and I’m pretty lost with this, I’ve already taken way to much time on this. I’m not an electrical or programming guy at all.
After reading some reviews it sounded fairly easy but now that I’m here I’m lost. I’m attempting to run a Window Wiper motor as a steering servo using remote control thru this board. Does anyone have a picture or basic wire diagram and screen shots on how to configure? Seems like a few folks have done this and I’ve love for some help.
Do I need the Potentimeter?
Does the power going to the Reciever come from 5V (Reg. Output) or VIN (Power Output)? Is that what powers the motor? Or does the Motor A & B out puts power it? Or does A & B just control it?
A basic diagram and screen shots of the computer config’s for steering would be very helpful.
Thanks so much to anyone that can help me!
Hello leftside34.
First of all, have you seen the jrk user’s guide?
pololu.com/docs/0J38
Please try following the instructions in the “Setting Up Your System” section of the jrk user’s guide. If you have trouble, let us know what step you got stuck on. Here are some additional tips and answers to your questions:
Before connecting anything to jrk, please plug it in to USB and make sure you can connect to it with the Jrk Configuration Utility.
To connect a feedback potentiometer to the jrk, you need to identify which wire goes to the wiper. Connect the wiper to the jrk’s FB line. There should be two other wires from your potentiometer: connect one to AUX and the other to GND.
If you want the jrk to do position control, where you command the jrk to move the system to a particular point and the jrk gets the system to that point using PID, then you need to connect the feedback potentiometer. For a steering servo I think you would definitely want position control.
You will need to connect a suitable power supply to the jrk’s two larger GND and VIN connections. Do not connect your power supply to the smaller GND and VIN pins because they are not designed to handle a large amount of current!
I recommend that you first get feedback working and control your system through USB using the scroll bar in the Status tab of the Jrk Configuration Utility. Once that is working, you can change the Input Mode from Serial to Pulse Width and then get the input from your RC receiver working. To connect an RC receiver to the jrk, you only need to connect the jrk’s GND to the receiver’s GND and connect the jrk’s RX line to one of the receiver’s signal output lines. The receiver must be powered from some power supply that is in the right voltage range and can supply enough current. You may find it convenient to power the RC receiver from the jrk’s +5V line, but this is not required.
The motor A and B outputs can NOT power the receiver. You should connect those outputs to your motor leads and nothing else.
–David
Hi David,
Thanks for your response I really appreciate it. The project got delayed so I will have a little time to work on this now. Hopefully with your helpful info. I can resolve some of the issues and get this up and running soon. I’m sure I will have more questions along the way.
Thanks again,
Scott
Hi David,
Thanks for your info. and I had some time to go through this. I have the motor controlled via usb to computer with a feedback Pot. At this point I’m unsure what I need to do to set it up as a steering servo using RC.
I will be using RC to control the motor but how to I set the stops?
At this point do I need to move into the RC side of the set up for this?
Or can I set the stops prior to switching over to PWM?
Again this will be used for steering with an RC controller using a wiper motor. I’m getting closer! Just a few things are just over my head at this point.
Thanks,
Scott
The basic strategy you should use when setting up the jrk to do position feedback has two parts:
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Set up the Feedback side of the system so that setting Target to 0 causes the output to go to one end of its motion while setting Target to 4095 causes the output to go to the other end. To limit your system to a smaller range of motion (closer stops) you can use the Feedback Scaling settings. This can be done before switching over to Pulse Width (RC) input mode.
-
Set up the Input side of the system so that you can reliably set the Target to 0, 4095, and a range of values between. Since you are using an RC receiver you will definitely need to change the Input scaling settings to achieve this. You can click the “Learn…” button in the input tab. Reasonable input scaling settings for the Pulse Width (RC) input mode would be:
Input Absolute Max: 3300 (2200 us). Your receiver should never emit pulses this long.
Input Maximum: 2850 (1900 us). Your receiver should emit pulses a little longer than this when your stick is at one extreme.
Input Neutral Max: 2400 (1600 us). Your receiver should emit pulses shorter than this when the stick is at neutral.
Input Neutral Min: 2100 (1400 us). Your receiver should emit pulses longer than this when the stick is at neutral.
Input Minimum: 1650 (1100 us). Your receiver should emit pulses a little shorter than this when your stick is at the other extreme.
Input Absolute Min: 1200 (800 us). Your receiver should never emit pulses this short.
Target Maximum: 4095.
Target Neutral: 2048. This is where your output will go to when the stick is in the neutral position.
Target Minimum: 0.
–David
Hi All,
I’m slowly making some progress with this project. At this point I’ve been able to power the motor but haven’t set up the RC side just yet. My issue at this point is that I’m unsure if I should be able to control this through the computer the same as it would for an RC setup controling steering. I can get the motor to go “left” and “Right” but in continuous operation. Is this where the RC Transmitter steering wheel comes into play and controls this? I’m so close!! lol. I hope what I’m describing makes sense. I used the setting listed below but again I’m still working on wrapping up the connections to the RC Reciever and checking it out that way.
Thanks for any more tips and or advice you may have!
Scott
Yes, you should be able to control the through the computer the same as you would for an RC setup (by setting Input Mode to None and then using the “Manually set target” box). The input from the computer and the input from the RC receiver are just two alternative ways of setting the jrk’s Target variable which is the desired position of the system.
It sounds like you haven’t succeeded in doing step 1, which is to set up the feedback system. I recommend doing this before trying to get the RC receiver to work. Did you remember to set the Feedback Mode to “Analog”? After doing that, does the jrk’s Feedback (as shown in the plots window) go from ~0 to ~4095 as you move the system through it full range of motion?
–David
