AX2550 - controller resets when driving one motor in one direction

14 years 8 months ago #29525026 by Steve

We are using a Roboteq AX2550 on a new project (a remote controlled vehicle).

We had our first field test yesterday, and ran for a total of maybe 1 hour.

The controller has started to reset whenever we drive forward - I had to reverse the vehicle all the way back to the workshop.

Further investigation shows that the controller only resets when the RHS motors are asked to turn forward - LHS motors are fully controllable, and RHS can be rotated backward at full speed.

As soon as any forward demand in put on the RHS motors, the controller shows a solid 8, then starts it\'s NO CONTROL message (it gets as far a \'C\') then is responding again.

We have disconnected the RHS motors so there is no load on the drive, with no change in behavior.

We are using the controller in mixed steering mode, 120A limit with RC inputs for both channels.

I\'ve seen mention of MOSFETs desoldering themselves in other forum posts. Is there anything we can check or replace ourselves? We are experienced electric vehicle developers, so have replaced many MOSFETs over the years, and would prefer this to returning the drive.


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14 years 8 months ago #29525027 by cosma
It sounds like when asked to move forward, the power output causes a short on the power supply which then causes a power on reset.

Try operating the controller with the PC utility. Use a separate power supply on the yellow wire input. This way, the controller will not reset whatever happens to the main battery voltage.

Insert a fast automotive fuse between the red wire and the battery (30A or less). This is to prevent further damage in case it is confirmed that a short occurs when driving that channel forward.

If confirmed, then this would mean that one or more mosfets are damaged.

Replacing is not necessarily hard but typically the damage extends to other parts of the output bridge, including the mosfet driver.

Please contact us at This email address is being protected from spambots. You need JavaScript enabled to view it. for repair instructions.

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14 years 8 months ago #29525035 by Steve
As per your email instructions, this drive was returned to you on the 8th June.

Can you confirm that you have received the drive and if there is any progress.



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