in response to this question from @n5vei : Vex Cortex PTC divided on ports?
Here is a link to the User guide: VEXnet-UserGuide-20150210.pdf
Page 14 has the following:
Overcurrent protection: Motor Port 1 through Motor Port 5 shares one 4 amp circuit breaker. Motor Port 6 through Motor Port 10 shares a second 4 amp circuit breaker.
And here’s a nice picture. Note the two yellow-orange squarish components in the lower left corner of the picture. Those are the PTC devices.
Thank you sir!
A possible reason that you had students thinking it was three circuits is that the power expander module has an additional PTC in it for the motors connected to it, so it basically functions as a third breaker in a robot using the expander. I coach my teams to break up the load across all three to reduce motor dropouts.
Wait, so is it recommended to put the Y-Cables on the CORTEX instead of on the expander(Like put one on 1-5 and the other on 6-10)? And I already heard this before, but I didn’t know if the expander had one or two.
Power Expander has one PTC device. You can use Y cables effectively on the Cortex to motors, on the Power Expander to motors, on the Cortex to Power Expander ports, or even on a Power expander port (out) to Power Expander port input. You do that last one to increase “fan out” or the ability to drive more motors from a single port.
The specs on the power expander are as follows:
So adding an expander would provide three sets of 4 Amp circuit breakers. Two on the Cortex and one on the expander. Divvy it up as you see fit.
Many of our teams powered a four motor chassis with the expander and then divided the left and right lift and claw motor power across the two Cortex groups.
*Your mileage may vary.
