On to some more nitty gritty about wiring.

Motor-to-Motor Controller Connection

VEX motors will plug into the motor controller either of 2 ways, with matching colored wires (red-to-red), or with opposite-colored wires (red-to-black).

wiring-matching

wiring-opposite

How come you can plug it in either way, and what’s the difference?

When you plug in the motor controller with matching colors, the motor will turn in its standard direction (counter-clockwise), when you send motor power instructions that are positive (+1 to +127). When you plug the motor in the opposite way, positive power numbers will result in clockwise movement. Up is down and down is up. 

A Real-Life Example

Why would you ever want to do this? Let’s say you have a shaft that’s lifting an arm that’s so heavy, it needs 2 motors in order to lift it (see below). If we turn both motors to, say 100 power (positive / counter-clockwise), they will be fighting each other, trying to spin the shaft in opposite directions simultaneously.

motor-polarity-fighting

So instead, we flip one of these motor controllers to opposite colors (red-to-black wiring), and the motor on the right is now going in the same direction as the motor on the left. You can now program both motors to +100 power and they will work together.

motor-polarity-working

Buy why wouldn’t I just program the motor on the right to be -100 power in my program? The answer is, sometimes you can’t. The perfect example is when the 2 motors above are connected together with a Y cable, and plugged into a single motor port on the cortex. Now when I program my motor module for, say Port 5, I can set my motor module to +100 power, and the 2 motors will work together. Otherwise I’d need to use 2 separate motor ports and program them separately.

Connecting 3-Wire Extensions

When you use a Y cable, or when you need to add an extension cable to your motor controller in order to reach the cortex, you’re plugging a 3-wire cable into a 3-wire cable. Here, there’s only one thing to know: All 3-WIRE CONNECTIONS MUST HAVE MATCHING COLORS, or else they simply will not work (that goes for the 4-wire motor encoder cables too).

3-wire-matching

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