[FTC]: Wiring Motors to Motor Controllers

[F Elliott]

We wish to mount two DC motors per side that are mechanically linked, for a total of four drive motors. Lets assume we have plenty of motors and controllers to build it anyway we wish. Two options:

A. Use one motor controller with two motors per channel with the motors on each side wired in parallel and connected to one channel (L, R) being careful of shorts.

B. Use two motor controllers and connect one motor per channel with each motor being programmed on a separate channel (LF, LR, RF, RR)

QUESTIONS

1. Which approach would give us better drive power? Better reliability?

2. Given that the motors on each side are mechanically linked, is it necessary to use Option A or is it just a programming convenience or saves a motor controller?

3. Under Option A, wiring two motors in parallel to one channel should draw twice the current in that channel. Are the controllers able to reliably supply that?

4. Under Option B, if the two motors are always programmed as a sequential two-line operation, will that work or will the motors potentially "fight" one another?

5. Under option B, what if we wired the two front motors to one controller and the two rear motors to the second controller? That way, if one controller died, perhaps we'd still be able to drive?

In short, how would you wire and program the motors and why?

THANKS!

Photo of one side of the prototype drive. The shoulder bolts will be replaced with shorter bolts to eliminate the aluminum spacers outside the wheels.

http://friedbits.com/downloads/DriveTrain-20141118-5.jpg

[maths222]

We do option B with mechanically linked motors. Now to answer your questions...
1. B for both (I'm pretty sure for the 1st, I know for the 2nd)
2. Just convenient/saves motor controllers
3. Not fully, as each channel can supply up to 4 amps, and each motor can draw up to about 4 amps at stall torque.
4. The time delay of the I2C commands sending and the motor controller changing behavior is much greater than the time it takes to execute two sequential lines of code, so it won't matter.
5. You should definitely do that if you use two controllers. That has saved us in at least one match. NOTE: plug 1 into nxt port 1 and the other into nxt port 2; that way, if one fails, your drivetrain does not die.