Fisher Price

[frcchile]

Hello to all!!!!

We are trying to hang but with a Fisher Price motor and the gearbox and we want to conect two Fisher Price to one Jaguar, Can we do it?

Thank you !!!

[IndySam]

NO.


<R55> A. Each CIM motor and Fisher-Price motor must be connected to one and only one approved speed controller. These motors must not be connected to relay modules.

[Andrew Schreiber]

I encourage you to read R49. In addition to IndySam's comment.

<R49> Each power-regulating device (speed controller or relay module) shall control one and only one electrical load (motor, actuator or compressor).
A. Exception:Multiple low-load, pneumatic solenoid valves may be connected to a single relay module. This would allow one relay module to drive multiple pneumatic actions. No other electrical load can be connected to a relay module used in this manner.

[Jon Stratis]

If you want to make it easier on your programmers, hook each of the Fisher Price motors up to their own Jaguar (or Victor), then use a PWM Y cable (two should have come in the KoP) to connect both of the speed controllers to a single PWM port on your Digital Side Car. Thus in the code, these act like a single speed controller/motor, and you can be sure they are always being set to drive in the same direction and at the same speed.

[John G]

You would still need a PID loop to ENSURE the same speed. Without a PID loop, they will not spin at the same rate, causing one motor to hold back/ work against the other motor.

[apalrd]

Not necessarily. While it is true that operating one backwards could cause the wiring bias of the Fisher Price motors to cause problems, as long as they are physically spinning the same direction they should be fine. Look at all the teams with four CIM's in their drivetrain, I don't think they have independent control of each of them. Or those who have a CIM and a F-P, they don't need independent control either. As long as they are both going the same direction and geared the same, they will be fine.

[Al Skierkiewicz]

Not sure that is the case. As the cost of a motor goes down, so too does the production controls. There are variances motor to motor. Two motors linked in a common gearbox will run together since there is no other way for them to run. You need to feed the same values to each controller to insure that the motors share the load.

BTW, two FP motors connected to a single speed controller would exceed the max current of the controller when the motors are at stall.

[RyanN]

I would not run them in a PID control loop. Bad idea.

Do what others have said and run a Y. No reason not to. The motors will run about the same RPM, and even then, the gears make up for it with friction, so each motor is actually working to move the robot rather than working against the other motor.

I would not setup different PWM ports or run them in a PID loop. That's asking for a lot of back-feed into one of the motors. We've fried a Victor before by doing that when we were just moving the robot down the hall. Jaguars will be worse since their fan shuts off when not in controlled use.

[Rohan J]

I'm a mechanical guy, but my two years of computer science courses are telling me that it shouldn't be difficult to just make them appear to be one speed controller in software, especially if you are using C++ or Java.

You probably wouldn't want to put them through one speed controller anyways. The maximum current you are allowed to supply to a speed controller is 40A. If the two FP's were drawing 20A each, you would get about 0.25Nm of torque. If each FP was drawing 40A, you'd get 0.50Nm. Keep in mind that an FP stalls at 70A, and 0.45Nm.

Also, my team is using a winch, driven by a CIM and an FP geared to the same speed as a CIM, and there is no PID loop, and since we are using a CAN bus instead of PWM, we didn't use a Y-cable. We're simply telling them to turn at the same time, same speed, and same direction. Seems to be working fine