Troubleshooting help with micor dual serial motor controler

How is the best way to troubleshoot this? I am using the controller with a basic stamp 2 on a BOE. At this point everything is on a breadboard. I have a program that simply ramps two motors up to speed then ramps them down. It all seems to work great but I can only get it to work once. by that I mean when I first turn on the stamp board it works great, the motors ramp like they are supposed to but it requires a power off reset for the controller to run the motors again. If I simply reset the boe the program runs but the motors don’t. I am running the controller and the motors from the regulated 5v from the boe. my initial thought is noise from the motors causing an issue with the controller, so I placed caps across the motors, across the reset pin the controller’s logic supply. The user’s guide indicated I could run both from the same supply. Any suggestions would be appreciated.

Also in the mdsmc user’s guide page 10 there is a sample program for the stamp. Line 2 of the program initially sets the serial line high. What is the significance of that?


You definitely cannot power your motors from the BS2 voltage regulator, which is good for a few dozen mA.

- Jan

Thanks Jan,
I appreciate the fast response. I added a second power source for the motors, and seems to have resolved the problem. I am really impressed with the controller. it’s so small and yet so powerfull.

I am still having problems with this controller. It is occasionally inconstintant. The program simply starts both motors and monitors a switch to adjust the speed. I never exceed a speed value of 100.

Most of the time it works, but occasionally only one motor will start. or one motor will start and pulse on and off, or both motors start and stop with in a second. The program on the stamp appears to be running,I say that based on strategically placed freqout commands that sound when they should. I placed pauses in various places thinking maybe the controller was not up to full power before the serial command started and added a pause to set a delay after a reset, and various other places. I slowed the baud to 1200.

I have no problem with my program or hardware when I test with LEDs instead of motors.

I have 4 AA batteries to power the controller’s motors supply and the controller’s logic supply from the regulated 5 volts from the BOE (not the BS2) The Boe is powered with it’s own set of 4 AA batteries. I have changed all 8 batteries with new ones and measured the voltage while the motors were running as per programmed and are at sufficiant levels per the user’s guide. All batteries are alkaline.

It makes me think my problem is due to noise from the motors. Are there any recomended circuits to reference to that may help if that is the problem? Or do you have any suggestions? I’m sure there is a simple answere, but I am getting frustrated.

In general, alkalines aren’t that great, so I recommend NiMH batteries.

What are the specs on your motors? Your LED test does indicate that noise is the problem. You can improve noise problems by routing the power lines away from the signal lines and twisting each pair of motor leads together. You might also add some capacitors to the Vcc line and your motor supply. Also, how do you have your supply grounds connected? Try connecting them as close to the motor controller as possible.

- Jan

Maybe alkalines aren’t that great, but I know what to expect from them. I believe they are quite capable of handling the power requirements of the simple tests I am performing.

The only spec I can give on the motors is stall current, which I determined by meassuring current when manually stalled. That current at 6 volts is just over 1 amp (less than 1.1) on each motor. due to that fact I am not running the motors beyond a speed value of 100 and while performing my tests the only load the motors have are the gear train and wheels spinning freely in the air. the motors are definitely not stalled. the problem that occurrs is when the motors are first started, so I find it hard to believe i am trigering the overcurrent protection of the controller. I do have twisted pairs to the motors. I do have capacitors. I have the controller on a bread board and all grounds are connected at that point.

I am beginning to think I have a timing problem with the serial comms. As I change the placement of pauses I get different symptoms.

I will reread the user’s guide and see If I overlooked anything.

Thanks Jan.

Can you run your motors off of 3 cells? That would help reduce the current and therefore the noise. Do you have access to an oscilloscope so that you can look at what the various lines are doing?

- Jan

As an attempt to troubleshoot I will give the three cell option a try. But the specs in the user guide indicate up to 9 volts and by not pushing the motors to full speed and also with a minimum load I feel comfortable that i am not exceeding the current limit. Yes I do have access to on oscope, I’m sure there is noise on the lines, but I don’t know how much the controller can tollerate. What lines are you speaking of? Are there specs somewhere that would clarify how much noise the controller can tollerate?

Ultimatley I had planned on running both my bot and my contoller from the same battery supply, which would require a minimum above 5 volts. I was under the impression that I could do that. Is that not possible?

First of all, thanks for the responses I do appreciate them. I don’t really expect pololu to hold my hand to resolve problems, I have, though, asked for information that I could access on my own above and beyond the user’s guide. I have not received any response to that request. I beleve I may have a simple programming issue regarding timing, and have stated that. Yet no response to that. There is no doubt in my mind that this is a good product, and that I will eventually resolve my issues.

Good Luck.

I’m not sure what you expect us to tell you. I think your first complaint (no response to request “for information I could access on my own”) is about a noise spec., which we don’t have. Generally, your voltages (on all lines you control) should be within a few hundred mV of what you are trying to set.

Regarding no response to your timing problem suspicion, that’s just something you’ll have to figure out (or at least provide more details). What you wrote apparently didn’t make anyone think of a solution, plus it looked like you were on to something, so it didn’t get a response.

Regarding your comments on the current, citing the 9 V spec is irrelevant since we’re trying to reduce noise. Even if your average current is low, your peaks are around your stall current. If you lower the voltage (and increase the duty cycle to compensate), you might get better results. The main thing is, it’s hard to tell what’s up without looking at a scope. Once you can see your signals, you can also see what improves their quality.

- Jan

Sorry Jan, I lashed out a little bit. I do appreciate your responses. I was not trying to completely rely on pololu, or you for that matter, but other forum members that could offer their experience.

I am supprised you are the only one that offered help.

Also to let you I am getting a handle on my problems.


Just a follow up. I did resolve my problem. It ended up being A stupid mistake on my part. I overlooked the delay required after a reset, duh. the contoller has been working great since. I am able to run at 6v, and also I am successfully running the controller, the processor and the motors off the same set of batteries.

Once again thanks for your help, your time, and your replies.

I’m always happy to reply to a topic when I think I can offer reasonable help. Problem is I have no experience with this motor controller, your motors, the BS2, or the BOE Bot platform. So there really honestly wasn’t anything I could add to the discussion. In this instance, Jan was your best resource.

I have been READING this thread, however, because I hoped I might learn something. I have. And I’m filing the information away for the day when I do use one of these motor controllers (two, actually… I’ve got a bot in mind that’d need them.)

Such is forum life. Glad you got everything working well.


Thanks for the reply benedict. No problems here.

If I see a forum post regarding experience that I have, I will be gladly share it. “Such is forum life”.

I looked at your profile and checked out your web link. Looks like a great forum. I will be spending some time checking it out. So many forums, so little time.