We are looking at adding the VEX Power Expander to our system this year. I have 2 questions.
First, what increase in output does the expander provide to the motors over the existing system.
Second, It requires a “PMW” cable for each motor. What is a PMW cable?
Thanks
The PWM cables are the 3 wire cables that you use as extensions from the cortex to motor controller or to the in Port of the power expanders. I’m not sure of the technical terms but in my experience, anything over 8 - 9 motors draws more than the battery can output and the power expanders splits up that current draw.
First, it doesn’t produce an increase in output, necessarily. It does allow you to use a second battery so you have 6000MAh available instead of the 3000MAh from a single battery. You can think of the power-expander as a powered signal repeater. It takes the signal from the cortex and uses the power of the additional battery connected to it to power all of the devices connected to it. This relieves the battery connected to the Cortex to power the Cortex itself as well as those devices directly connected to the Cortex. It also adds an extra layer of protection as is has its own circuit protection built in. Second, not PMW but PWM (Pulse Width Modulation). These are the cables that are connected to the motors. They are also the 2 and 3 wire extension cables that you need to run from the output of the Cortex to the input of the power expander. You then plug the cable from the device to the corresponding output of the power-expander.
Sorry for the typo… PWM. But the answer now raises a few questions.
Why would an extension cable modulate the pulse width?
Does it matter if it is 2 or 3 wire for the motors ( not the servos)??
If the motors are using the motor controller wire 29, Where does the controller go? before or after the power modulator?
There is no information about this device anywhere in the VEX site that I can find.
Thanks
The extension is from the cortex to the power expanders and has to be there wire. The motor controller is still between the power expanders and the motor.
look under the installation tab for information on how to use the power expander.
We have been trying to use a Power Expander and randomly our motors are stopping. When we disconnect the PE we have no issues. Any thoughts as to what might be going on? Could it be a bad PE?
@Powerbelly We ran into something similar tonight, and initially thought it was a bad PE. After a little more testing however, we chalked the issue up to a couple of bad extension wires.
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That doesn’t make sense when it works without the PE and doesn’t with, but I’ll check with my team and see if they have any extension wires that could be bad.