12 Motors on one Robot


#1

If we wanted to look into having 12 motors on our robot how would we do that? There are no limits to the number of motors we can use but are we limited to the number of ports on the PDP? Is there some kind of PDP expansion board?


#2

You are limited to the slots on the PDB board. You can’t add a second PDB.


#3

You’re effectively limited to 16 (not 12) motors by the slots on the PDP. There are minor exceptions in the manual (sometimes you can drive two motors off the same motor controller, but only very weak ones so there’s no real point) but in general you’re limited to 16 of which 8 can get 40A breakers and 8 can get 20A or 30A (or less) breakers.


#4

You are not allowed a second PDP, and are limited to 1 motor per PDP spot*. 12 Motors isn’t crazy, we ran 15 at our first event last year, and wouldn’t be surprised to max out the PDP this year.

  • With exception of select automotive motors.

#5

How did you run 15 motors with only 12 slots? I’ve heard of teams using Pdp extension panels in the past to allow a small increase in # of slots but am not sure where to find them


#6

You have 16 slots on a PDP. They used 30 amp or 20 amp breakers for 7 of their motors.


#7

There are 8 40A slots and 8 20/30A slots for a total of 16 slots.

http://www.ctr-electronics.com/pdp.html


#8

That may be in reference to a few portions of the IFI control system era where two separate and different power distribution blocks were used. You might also be thinking of the VRM, which can’t be used to power motors. There is not currently a legal way to power more than 16 “standard” FRC motors without the aforementioned exception for certain low power motors


#9

So there’s no way to have more than 8 40 amp motors? How do teams run 6 motor drive trains then? In my experience, most robot mechanisms require motors than run at 40 amps.


#10

You have to get a bit crafty with planning, but it’s certainly doable. Using more motors on the same mechanism will reduce the load on each, and you can usually get away with going over the breaker’s amperage rating for a few seconds during sudden accelerations (like climbing).


#11

You run your 6 motor drivetrain with 6 of the 40A slots, use the other two for really heavy-duty stuff, and design your mechanisms to need 30A or less (maybe using two motors to do the work of one CIM).


#12

What kind of motors would work under 30 amps? 775 Pros?


#13

Excellent question Mr. F22 Raptor


#14

Last season we ran a 8- 775 drivetrain and just put 4 motors on 40 amps and 4 on 30 amps. We never tripped a breaker and it worked perfectly fine. It allowed us to put our climber and elevator on the 40s still.


#15

All FRC motors “work” under 30A, but the more load you put on the motor, the more current it’ll draw to support that load. Reducing the load on an individual motor can be accomplished in a variety of ways, but the most universal is to add more motors to the mechanism in question. In some cases, it may be wise to put a motor on a lower amperage breaker to prevent damage to the motor and/or mechanism. If you’re regularly tripping breakers, you may want to adjust your gearing (even if it slows down the mechanism) and look at other ways to reduce the load on the motor, like counterbalancing or adding springs to arms and elevators.