Power Expanders

They allow you to use an extra battery to distribute to the motors so they’re not all being powered by one battery

They allow you to use an extra battery to distribute to the motors so they’re not all being powered by one battery

If you are competing in competition then you still have the 12 motor limit regardless of if you have a power expander or not. A power expander gives you 4 motor ports however these must be controlled from motor ports on the cortex. All the power expander does is power these 4 ports, spreading the load of the motors across 2 batteries and offering increased battery life and performance.
To increase the number of motors you can use I would recommend Y- Cables, but remember that in competition you will still have the 12 motor limit while competing with a cortex robot.

That’s correct.

No it doesn’t. Basically you have 3-Wire extension cables connected between the CORTEX and the power expander, with one wire representing one port for the power expander (AKA you’ll have 4 wires that go between the CORTEX and the expander). You use Y-Cables, as what @Download Complete said to split one port into multiple ports for multiple motors. Note: You cannot control an individual motor that is connected to a Y-Cable. For an extra note: I would NOT recommend having more than 1 Y-Cable on the power expander, for the reasons of distributing the load between all of the PTC’s.

You can find the Y-Cables here: https://www.vexrobotics.com/extension-cables.html

This is correct.

You can use Y-Cables wherever two motors are supposed to do the same things, so this could apply to any system (motors on one side of the base, etc)

If you have one motor connected to the Y-Cable go 100 RPM, the other motor connected to the Y-Cable will go 100 RPM as well. But, the direction may be different depending as to how you connect the motor to the motor controller. The motor controller translates the 3-Pin wires that is connected to the expander or CORTEX to the 2-Pin wires which would be connected to the motors. If you switch the polarities of the 2-Pin wires (AKA do black to red and red to black, instead of black to black, and red to red), then the motor will spin a different direction.

If you have a 4 motor drive, I would not suggest having a Y-Cable on the drivetrain. But, if you’re having 6 or more motors on the drivetrain, I would suggest having it be on the drivetrain.

Not always the case: some y-cables only work when the motor controller is plugged into the cable in a specific orientation. Very annoying to debug

I think you’re getting confused between switching the orientation of a 3-Pin vs switching the orientation of a 2-pin. The 3-Pin wires only work in one orientation, but I am pretty certain that a 2-Pin will always work when plugged in, regardless of orientation (Considering that no wires are cut, shredded, or ripped). By switching the orientation of a 2-Pin, you’re switching the direction of current for the motor, thus reversing the direction the motor turns.

Here’s my illustration as to how I usually wire the motors on the power expander:

Here is a more clearer image as to what it looks like to power a motor via an expander.

The analog input is optional, but you are able to connect it to the CORTEX if you would like to get the voltage of the second battery.
EDITS//: Added image and more information

Whoops, I read your previous post wrong. I thought you were referring to 3-pin wires being flipped when plugged in. You are correct, switching the orientation of the 2-pin wires (the connection from the motor to the motor controller) will work as you explained. My bad

Just a note to help clarify the situation. There are 10 motor ports on the Cortex. Each of those ports sends out a specific signal determined by the programming. Ports 1 and 10 are two pin ports and have built in motor controllers and allow you to connect the two wire motors directly to them. Ports 2-9 are three pin ports and require a motor controller to be placed between the port and the motor. The signals that run the motors ONLY come from these 10 ports. A Y-cable, which is a three wire device, allows you to connect a three wire port on the Cortex to two motors, each with a motor controller between the Y-cable and the Motor. This splits the signal from the Cortex port to each of the two motors. There is NO way to independently control the two motors that are on the Y-cable, except for the reversing the polarity of the two wire connections, which will run the two motors in opposite directions. However, those two motors will always run at the same power and will run as programmed for whatever Cortex port they are connected to.
A power-expander has no way of controlling motors. It is merely a device that takes the control signal from a Cortex port delivers that signal to the corresponding motor, but that motor is powered by the second battery connected to the power-expander. For example, a motor that is in port 3 of the Cortex can be run from the power-expander in the following manner. Run a three wire extension from port three of the Cortex to an input port of the power- expander, then run a motor controller from the corresopnding output port of the power-expander to the motor. The signal that controls the motor comes from port 3 of the Cortex, but the motor receives its power from the battery connected to the power-expander.
I hope this is clear.

Also of note: the power expander allows each port to only power (supply current to) one motor.
By ycabling from 4 of the cortex 3 wire ports, and connecting one end of each y-cable to the power expander, and one end to a motor controller/motor, it’s possible to separate the load very evenly, without having to use ports 1 and 10.

This is not true.

I think you’re misunderstanding what he’s saying. He’s not saying that’s the limit. He’s saying you can put all 12 393 motors each on their own port as far as power supply is concerned. You can have 8 directly from the Cortex. You power 4 of them from the power expander. Assuming you divide those 8 on the Cortex into 4 in ports 1-5 and 4 in ports 6-10, that’s 4 motors per ptc.

I wrote an in-depth (plain-English) article about the power expander that you might find helpful: https://renegaderobotics.org/power-expander-2-batteries-are-better-than-one/

You have 12 motors limit with Cortex w/o Pneumatics. No matter what you use, you have a limit of 12 motors in competitions. Physically, you can go as many as you like if you have power expanders and Y cables. But in competitions, only 12 without pneumatics and 10 with pneumatics