Backwards motor

[paulcd2000]

Hi everyone. We just realized that the way our motors are wired, we have one motor going backward when we tell it to go forward. Has anyone else had this problem, and how have they fixed it?

Thanks in advance

[xrabohrok]

This is probably a very simple problem. Your motor has probably been wired with reverse polarity: so you can probably just flip the wiring. Put the red wire to were the black one is, and vice versa.

That should help!

[Bharat Nain]

Originally Posted by xrabohrok

This is probably a very simple problem. Your motor has probably been wired with reverse polarity: so you can probably just flip the wiring. Put the red wire to were the black one is, and vice versa.

That should help!

on the speed controller that is.

[steven114]

Specifically on the motor output end of the speed controller (labelled M+ and M-). Don't reverse the polarity anywhere else! If you reverse the inputs (V+ and GND) you'll fry the poor controller...

[paulcd2000]

actually, the wires are right. red-red black-black, and if we change them, someone said we'd fail inspection

[FIRSTnameisJay]

My only concern with simply switching the wires is the actual performance of the motors. I might be wrong on this but those CIM motors travel slower when going backwards than they do when going forwards. Does anyone know if this is correct?

[Al Skierkiewicz]

Originally Posted by paulcd2000

actually, the wires are right. red-red black-black, and if we change them, someone said we'd fail inspection

A common misconception. The rule for wire colors is
<R81> All wires distributing power with a constant polarity (i.e., except for Relay Module, Speed Controller, or
sensor outputs) must be color-coded as follows:
• Use Red, White, or Brown wire for +12 Vdc and +5 Vdc connections.
• Use Black or Blue wire for Common (-) connections.

Since the wires to motors are not constant polarity, you may reverse these leads to allow the motor to run in the needed direction. You may also make the change in software if you are so inclined. You will not fail inspection for reversing the motor leads at the output side of the controller.

[charrisTTI]

Originally Posted by Al Skierkiewicz

A common misconception. The rule for wire colors is
<R81> All wires distributing power with a constant polarity (i.e., except for Relay Module, Speed Controller, or
sensor outputs) must be color-coded as follows:
• Use Red, White, or Brown wire for +12 Vdc and +5 Vdc connections.
• Use Black or Blue wire for Common (-) connections.

Since the wires to motors are not constant polarity, you may reverse these leads to allow the motor to run in the needed direction. You may also make the change in software if you are so inclined. You will not fail inspection for reversing the motor leads at the output side of the controller.

Remember that the left and right drive train assemblies are mirror images. If you wire them both the same and send the pwm ports the same values say 200, one set of wheels will be going forward and the other set of wheels will be going backwards. Nothing is wrong with the wiring, the software needs to send the opposite values to the left and right sides. If speed is x then 127 - x to one side and 127 + x to the other will have both sets going forward or both going in reverse

[dude__hi]

we just switched the leads going into the speed controller from the motor

[Cody Carey]

There is about a 2% difference in performance between running the motors forwards or backwards... you might not want to do that
instead, just go into the default codes' "user_routines" section, and where it says P1_y or P2_Y, (whichever joystick is messing up) change it to (p1_y*-1)
I believed that that worked for us anyway...

[steven114]

Changing the signal and changing the wires are functionally equivalent - the only way to compensate for a forward/reverse bias would be to mount the motors or to use some sort of closed-loop control.

[Cody Carey]

What do you mean to mount the motors?
I think that they are most likey allready mounted...
But you never know, huh?

[ida_noeman]

So, if we reverse the wiring, will the forward/backwards difference be gone? I.e. if we reverse the wiring, and set both values to 254, will they go the same speed?

[sanddrag]

Maybe not, maybe so. There have been reported differences in both motors and speed controls between forward and revers. When you are driving in the forward direction, make sure allyour pwm values are above 127. This should yield better performance. If your robot still doesn't go straight, manually fine tune the software or live with it because the bias is in the motor or your mechanical drive system.

[the_short1]

yes reversing output wires is easiest for coding, then to compensate for bias, drive the robot using pure code (no joystick) with pwm1 being left and pwm2 being right motors...
code:
pwm01 = 175;
pwm02 = 175;

then see if the robot pulls to the left or the right... if so adjust the numbers until it drives straight... you might end up with 175:180 .. then take the difference (5) and add it automatically to the drive code (pwm02 = p2_y +5) so it will send the joysticks value to the pwm but add 5 to compensate for bias.

or for somethign more complicated, use a percentage (as you drive faster add more to the joystick to compensate)

hope that helps