AX3500 polarity switching

Hi,

I am using AX3500 to run two DC motors. I am using joystik to control both motors. A microcontroller reads joystick position and sends commands to AX3500 through RS232 mode. I am encoutering a strange problem. The polarity of the both motors change suddenly while I am using the joystcik. I observed that after sometime (not fixed time), both motors start running backwards for the same joystick movement. It seems that this happens randomly regardless of the speed or load on motor. The other thing that I noticed is that when there is a direction change, both motors change direction, not only one. Has anybody experienced this kind of problem?

I am not using "Invert switch". I left it as it is. Does anybody know what's going on? Please help. It is urgent!

<P style="MARGIN: 0px">There was a problem on earlier versions of the AX3500 that was causing it to move in one direction vs another depending on the reset condition. This was fixed by removing the C8 capacitor.
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<P style="MARGIN: 0px">Note that the polarity change would happen only at power up or reset. Not during operation.
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<P style="MARGIN: 0px">If the C8 is present on your board (located near pin1 of the 28pin MCU), removing it should fix the problem.
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<P style="MARGIN: 0px">If it is no capacitor is present, then I suggest that you thoroughly exercise the controller with the roborun PC utility. If needed you can attach an USB joystick to your PC. This will let you determine whether the fault is in the controller or in your MCU code.
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<P style="MARGIN: 0px">Note that we have never heard of such a problem outside of the C8/reset condition discussed above.

Cosma,

You are right. It also switches the direction at power cycle. But it doesn't do every time the power is cycled or the controller is reset. Most of the time it doesn't change directions but sometimes it does. And yes, it changes direction while it is running.

I have a newer version of AX3500 that doesn't have C8 capacitor. I will try it and hope it works.

Thanks for the prompt reply.

I had that type of problem too although the direction often got reversed between power-ups. Removing that capacitor appears to have solved the problem though. Unfortunately, I've gone back to the 2550 because I have pretty severe heat requirements.