How many motors can you run at once?

[rwkling1]

Last year (2012), our team had a problem of running too many motors at once, we had 2 motors for our intake, and 3 for our shooter, and when we would drive (2 motors), we would stall out one of our motors. How many motors did your team run at once? and what techniques did you use to prevent something like this?

[Samwaldo]

If I remember correctly our 2012 bot gets the award for most motors
4 motors for conveyer belts/pick up
2 motors for shooting
2 motors to drive
1 motor to tilt shooter/shift electronics board and battery (for weight movement during balance)
1 motor for bridge device

Thats 10 (I might be missing one because I remember the number 11).

We placed bets to see which would burn out first. We NEVER changed one.

no problems, with so many motors. most were even running the whole time, and many under ALOT of wieght

[rwkling1]

Originally Posted by Samwaldo

If I remember correctly our 2012 bot gets the award for most motors
4 motors for conveyer belts/pick up
2 motors for shooting
2 motors to drive
1 motor to tilt shooter/shift electronics board and battery (for weight movement during balance)
1 motor for bridge device

Thats 10 (I might be missing one because I remember the number 11).

We placed bets to see which would burn out first. We NEVER changed one.

no problems, with so many motors. most were even running the whole time, and many under ALOT of wieght

That's so interesting, because for some reason our robot would always kill one motor even though we were only running 7-8 at one time

[Colin]

Do you know what motor specifically was stalling? It sounds more like a mechanical issue.

The only issue that I have seen with running too many motors (more than what you are describing here) is tripping the main robot breaker.

[rwkling1]

Originally Posted by Colin

Do you know what motor specifically was stalling? It sounds more like a mechanical issue.

The only issue that I have seen with running too many motors (more than what you are describing here) is tripping the main robot breaker.

It was one of our banebot motors for our intake

[T^2]

Originally Posted by rwkling1

It was one of our banebot motors for our intake

Almost certainly mechanical. This year we had 4 CIMs and 4 MiniCIMs running at the same time with no problems.

[apples000]

We had 6 cims on drive, 2 banebots for shooter, 1 minicim for deploying the climber, and a compressor running at the same time. In the past, we've had more. Its probably a mechanical issue.

[Dad1279]

As others have pointed out, it's not the quantity of motors, but the current that they draw. Do you have a way of measuring? Any motors getting overly warm?

[tickspe15]

In 2012 we had 12 motors

4 550s on drive
2 cim shooter
4 motors for intake
1 motor for bridge tipping(don't remember motor)
window motor for turret

[AlexH]

Originally Posted by tickspe15

4 550s on drive

you drove a 150lb robot with 4 550's?

how did that work out?

[Siri]

We had 14 in 2012. Our only confirmed failures were mechanical (or programming).

- (4) CIMs - 1 per swerve wheel, driving
- (4) BB 395s - 1 per swerve wheel, steering
- (2) AM-0912s - ball acquisition & lift
- (1) FP 9015 - shooter drive
- (1) Denso Throttle - shooter tach
- (1) FP 9013 - barrier crossing + ball intake
- (1) Window Motor L - bridge lowering

I'm not saying it a was a good idea, but it worked out ok. No systemic electrical issues with respect to it.

[Al Skierkiewicz]

The limiting factor is how much current can you pull from the battery before the voltage drop across the sum of all resistance exceeds the drop out for the voltage regulators. The internal resistance on a new, fully charged battery is .011 ohms. At 400 amps that will drop almost 5 volts. Figure another 2 volts for other resistance and you now are below the threshold at which the voltage can be maintained in the DSC. when the voltage falls down to 4.5 volts, the 24 volts and the 12 volts for the radio will drop out.
My recommendation is to limit motor usage to below 300-350 amps at any one time. You can do this by ramping up the motors you are turning on and using delays to prevent them from all starting at the same time. A motor that is not turning is in stall and will draw full stall current limited only be the series resistance of the circuit feeding the motor. Typical stall currents of 115 amps for CIM motor is common on an average robot.

I'd say you can run no more than the amount specified in the rules.

[Siri]

Originally Posted by Andrew Lawrence

I'd say you can run no more than the amount specified in the rules.

Technically, this was unlimited in 2012 (and 2013), because there was no cap on the allowed number of drive motors in COTS computing devices. You would hit the weight, cost or size limit eventually, though.
Section in full: K. drive motors or fans that are part of a speed controller or COTS computing device and fans included in the 2012 Kit of Parts.

There were also an unlimited number of certain servos and electrical solenoid actuators, which, while not "motors", do seem to fall into the OP's electrical concerns. However, it'd take some doing to compare them with a CIM, and I don't think that's actually what caused the referenced problem anyway. Electrical load issues can manifest in many ways--listen to Al (always, but particularly about the radio dropping out). But it's not the most likely explanation for stalling the same motor over and over again.

[rwkling1]

Originally Posted by rwkling1

Last year (2012), our team had a problem of running too many motors at once, we had 2 motors for our intake, and 3 for our shooter, and when we would drive (2 motors), we would stall out one of our motors. How many motors did your team run at once? and what techniques did you use to prevent something like this?

Thanks for the input guys, I'll have to do some testing over the summer!