A curious situation...

So we were testing our drive system last night and discovered a curious situation:

Of two motors in an AM SuperShifter, one is running opposite the other. Of course, this can often happen because one motor is wired backwards or its speed controller is receiving a reversed signal. In this situation, this is not the case.

The Jags that control both motors (tested individually) are both sending a positive voltage to the motors. The motors are wired identically. When each Jag is given the same control (via pwm), one drives the wheels forward and the other drives the wheels backwards.

We’re at the point where we think that one of the motors is actually wired backwards internally.

Any ideas as to what’s going on?

-Mr. Van
Coach, Robodox

Have you tried reversing the motors in the code?

Sometimes the motors run in opposite directions (usually happens uniformly on one side e.g both right side motors). If that’s the case your programmer can flip the motor in code to run in the opposite direction.

Which motors are these? CIMs?

people have reported random polarity designations on the BaneBots 775, but I haven’t heard of it happening on a CIM before.

Where did you get the motors from?

The motors are CIMs - all from previous KOP.

The problem occurs when the pwm cable is moved from one Jag to the other. When plugged into one Jag, the wheel runs forward, plugged into the other, the wheel runs backwards. (In each case, the other motor is back driven during the test.)

The code is the same…

-Mr. Van

even though this should be impossible to mess up since it fries the jags:

are the input voltages to the jag connected in the same way? (+ to +, - to -)

if power input to the jags is the same, I would test the same jag with different motors, this would confirm whether the problem is with the motor or the jag.

if the same jag induces different directions in different motors, the motors are to blame.

if the same motor turns different ways under different jags which have the same input voltage and signal, the jags are to blame.

let us know what happens, i’m curious!

For anyone who is interested, it turned out that indeed one of the CIM motors is wired backwards internally. It runs in the opposite direction of all of the other CIMs we have.


Has this happened to anyone else?

-Mr. Van
Coach, Robodox

We had a backwards CIM in 2010, ended up destroying a toughbox.

Acidentally programmed my drive code wrong so one CIM was fighting the other. Thankfully nothing was damaged.