Y Cable Question

VEX V5 Technical Support
#1

I had a question about y cable as i was looking through the rule book. I am planning on using 12 motors but i came upon this rule.

<R12> A maximum of one (1) VEX Y-cable can be used per Motor Port of the Microcontroller or
Power Expander. (You cannot “Y off a Y” to have more than two (2) motors controlled by the same
Motor Port.)

So theoretically i need 2 y cables in order for me to use 12 motors. but because of this rule i cannot. Can anybody clarify rule.

p.s. does anybody know if the power sent to the motors cuts in half if i use a y cable for 2 motors?\

THANKS

#2

This rule states that you cannot y off of a y. Meaning if you have a y cable, you cannot attach another y cable to it.

You can use two y cables; they just have to be separate.

#3

but it only says one y cable though

#4

wait never mind i got it

#5

Also, y cables do not reduce the amperage going into each motor (ignoring resistance, which increases). Instead, the motors draw more current from the same motor port. Be careful not to overload the Cortex’s 4 amp circuit breakers. There are two of them, for ports 1-5 and 6-10. 393 motors can trip them, even without y cables, if 4 of them are under heavy loads at the same time and on the same breaker. My team always puts 2 motors of our drive on each circuit, and 2 motors of the lift/flywheel/other scoring mechanism on each one. This way, if one mechanism places heavy load on the motors, such as a flywheel, it doesn’t trip the circuit breaker and reset the Cortex in the middle of a match. An example of this being useful is on our robot this year. When our flywheel first begins to spin up, the motors briefly draw so much current from the Cortex that the LCD screen shuts off. At least, it did last month, I haven’t checked since then, and we’ve rebuilt it, so it might be better now. The only reason the Cortex continues to work while the flywheel spins up is that only about 2-3 amps are drawn from each circuit, and that’s not quite enough to trip the breaker.

#6

The rule:

Does not limit you to ONE y-cable. It simple says a maximum of one y-cable PER MOTOR PORT. Meaning, as others have said, you cannot y off of a y.

You can use more than one y cable though on DIFFERENT MOTOR PORTS. They didn’t do the best job of stating this in the rule manual, but it’s there.

Edit: I didn’t realize the OP asked an official question which got a reply from Karthik:

https://vexforum.com/t/answered-y-cable-question/31824/1

#7

Can you Y off a Y cable through a power expander? That way you would still only be distributing power to 2 motors from each port.

#8

I’ve wondered this too as it isn’t specifically stated, but I’m pretty sure it would fall under controlling more than 2 motors with one port

#9