Fisher Price Breaker Size
 

What size breaker would you recommend using for a fisher price motor?
We were thinking 40 amp but I think it may be to high? Would 20 to 30 amp be better?

Thank you for any help you can provide.

DavidB

Re: Fisher Price Breaker Size
 

What application are you using it for? This will help determine what size you can use safely. For a generic FP, without knowing what it's being used for, I'd say 20A is too low, but then again, it might just be an orbit-ball shaker.

The rules are pretty much silent on the matter, which is probably why you're asking.

Re: Fisher Price Breaker Size
 

Well I believe we are using three. One will be for our lift system. So It will be spinning relatively fast but nowhere near free spin. The other two will be spinning faster but not constantly. The main one I'm concerned about is our lift system one. I'm thinking about moving it a 30 amp breaker since it will probably get hot.

Re: Fisher Price Breaker Size
 

As there are only two FP motors in the kit, and additional FP motors are not allowed in <R51>, only 2 of these motors can be used.

Re: Fisher Price Breaker Size
 

Fast does not constitute power.... or amperage... by itself

You need to figure out or have someone help you figure out the power consumption of the motors you are using.

A breaker will not help you with a "hot" motor... A "hot" motor is an indication that you are not at the optimum for that motor... or that you are pushing the motor....

Remember that you must change the gauge of your wiring if you use different breakers... You may always use a smaller gauge of wire...for that breaker but never a higher one. The lower gauge wire will not offer as much resistance because it is bigger. (The higher the gauge of a wire.. the smaller it is...)

You can push more current through low gauge wires than you can higher gauges just like pushing water through a big pipe. (sort of..)
but remember that resistance goes up with temperature so hot wires are more resistant than cool wires.

You want cool wires...it will gain you efficiency...

The main thing is to figure out what is the amperage load that you are needing to pull through that wire/breaker system.

Good luck with this!!

Re: Fisher Price Breaker Size
 

A proper mechanical design should never trip it's breaker unless a very abnormal condition exists. Take a look at the motor curve, see what torque the motor can produce at the current your desired breaker can supply, and design your system for the motor to be loaded less than that.

I traditionally try to use the largest breaker allowed, since it will result in being able to run your system with a higher load on the motor.

Re: Fisher Price Breaker Size
 

If your using three FP you will not be in compliance with the rules.

If an FP gets hot you're in for trouble. These are fan motors. When they get a bit too hot the plastic fan starts slipping and fails to spin making it even hotter. You may want to consider additional cooling.

The peak power point on the FP is 40 amps at 7500 RPM. I would say that you can safely operate at this point only at 7500 RPM and with additional cooling. If you trip this breaker at lower RPM then you are geared too low.

30 amps is probably a good sizing. It's best to make sure that you are geared such that the motor runs between 7500 and 15000 RPM and that when loaded it does not fall below 7500.

Re: Fisher Price Breaker Size
 

Only 2 FP motors are allowed and they must be connected to 30A minimimum breaker per the rules. I recommend speed controllers over relays, since the relay is only rated at 20A by default.

Re: Fisher Price Breaker Size
 

I'd appreciate seeing which rules on this. I'll go with you on the speed controllers, referencing <R54-A>, but I didn't see any rules on minimum size for a breaker (other than in the wiring rules, which are wires for given sizes of breakers).

Re: Fisher Price Breaker Size
 

I don't want to get into symantics here, but a 20A relay will burn if it is pushed beyond its limits. One stuck ball and the FP motor will push the current limits before it too burns out.With a relay, there is no stopping the destructive current and possibly both devices will be lost. A speed controller handles the current surge better and may go into protective shutdown rather than release the magic smoke.

You mentioned wire gauge, the fact that FP motors spec a certain guage makes it mandatory to use a device that can handle the current required of that guage. Sure, it may only draw 15A, but catastrophic motor failure in a stall condition may draw upwards of 50A from the FP motor. Avoiding wiring fires is always desirable. Better to plan ahead of the safety inspectors than to hope you won't be caught in violation.

Re: Fisher Price Breaker Size
 

IMHO the application rules are R46A and R54A.

You have to connect the FP motors to a Jaguar or Victor. A relay is not allowed.

You can supply the speed controller with 20A, 30A, or 40A and it must be dedicated to that speed controller.

20A may be a better choice if you are not sure that your gearing allows the FP to run fast enough not to burn itself up.

Re: Fisher Price Breaker Size
 

Just a personal preference here. 20AMPs

No science or anything behind my reasoning (well... actually there is, but I'm not going to get into the heat dissipation stuff...)

That little motor has to get rid of a lot of heat just at 20AMPs. At 30 or 40AMPs, I can see that motor going up in smoke in a hurry if something goes amiss. At 20AMPs, you at least have a few trips before it really starts damaging the motor.

Re: Fisher Price Breaker Size
 

Jim, I'm not really sure what your post is trying to say.

The FPs must be connected to a speed controller based on rule <R54-A> (as Eric mentioned).

These speed controllers can then be connected to 20, 30, or 40 Amp breakers. The required wire gauge is based on the breaker used.

If someone wants to run an FP off a 20 Amp breaker they would be allowed to do so. They could then use wire as small as 18 gauge to wire this branch. Depending on where on the torque/speed curve the motor is being run, this may or may not produce desired performance, but it is perfectly legal.

In fact, you could wire your CIMs through 20A breakers if you wanted (note: this is almost certainly a bad idea)

Re: Fisher Price Breaker Size
 

In my wiring, I treat the FP as equivalent to a CIM.This motor is powerful and fragile. Allowing only 20A of current is pretty low for this motor, but I do not know what applications you have in mind for it. I prefer to stay on the high side of the curve rather than the low side.

Re: Fisher Price Breaker Size
 

Nippon-Denso 18.6
Nippon-Denso 18.6
Keyang 11.8 19
Fisher-Price 70
Globe 21.58
CIM 133
Mabuchi 6.2
Banebots 37
Compressor start 25
These are the stall currents for the motors in the 2009 KOP.

<R54> All electrical loads (motors, actuators, compressors) must be controlled by relay or PWM output signals sent by the Digital Sidecar to an appropriate power regulating device
A. Each CIM motor and Fisher-Price motor must be connected to one Victor or Jaguar speed controller. They must not be connected to relay modules.
B. Servos must be directly connected to the PWM ports on the Digital Sidecar. They must not be connected to speed controllers or relay modules.
C. If used, the compressor must be connected to one Spike relay module.
D. Each other electrical load (motors or actuators) must be connected to one Victor or Jaguar speed controller or one Spike relay module.

Please note that only motors that are 20 amps or less stall current can be powered by relay(Spike) as that is the relay specification. An exception to this rule is the compressor which has a start current more than double it's run current. For this relay only you may substitute (read this as "should") a 20 amp circuit breaker in place of the relay mounted 20 amp fuse.

Any team may choose to run any motor from any breaker as long as the current rating and wire size rules are maintained. However, sound electrical practice and the rules allow you to size your breaker/wire/motor appropriately.
The 2009 game is unlikely to cause high currents in drive motors. That being said my normal recommendation for #10 wire to feed CIM motors and FP motors may not produce significant gains in this year's design only. Electrical rules allow you to use #12 wire with 40 amp circuit breakers (See R45 for all specifications) and #14 wire with 30 amp breakers. Therefore, should you desire maximum performance over all possible game conditions, my recommendations would be for #12 minimum for FP and CIM motors fed with 40 amp breakers. The Banebot motors can be fed with 20 or 30 amp branch circuits depending on your design, transmission and intended use. Please be advised that the Denso, FP and Keyang motors have internal thermal breakers in addition to any external electrical protection you provide.

Re: Fisher Price Breaker Size
 

This year, any Spike may be operated with a 20 A circuit breaker in place. (Previously, only the one on the compressor could be replaced.)

Re: Fisher Price Breaker Size
 

I believe that is a misprint, so I am awaiting an update. IFI specifications for this part require a 20 amp fuse.

Re: Fisher Price Breaker Size
 

I have never seen any good reason to only allow it on the compressor. I'm aware that the compressor was blowing the 20A fuses and thats why they allowed it, but why stop there, who cares if we put the breakers in the other spikes too, sure, they'll probably never blow, but why run the risk of one blowing and losing that device for the rest of the match, when it could come back in a second or two.

Re: Fisher Price Breaker Size
 

Actually this year you may do this for any relay per <R59-F>

Re: Fisher Price Breaker Size
 

This is an IFI recommendation that First has applied in the past. Compressor start can go as high as 25 amps but run is only 10-12 amps. This is a guarantee to blow the fuse even though it is an extremely short duration. However, used in other services, a breaker could easily allow more than 20 amps continuous without trip which is enough to destroy the relay.

Re: Fisher Price Breaker Size
 

We are using 40 amp breakers on our FP motors because there are times when we want that extra power kick. The FP motor can handle 40 amps but only for short periods of time at high RPM. We know we could conceivably burn up a few if something goes wrong (gearbox jam, stall, etc).

More important than breaker sizing is watching your loads. FP motors have a very distinct smell when they burn up (the insulation on the motor windings burns off). The first time you blow one up, you won't forget it.

Watch your loads! Don't rely on the breaker to save the motor.

-John

Re: Fisher Price Breaker Size
 

John's advise is sound (as always). The FP suffers at "high loads" because it requires active cooling. Look at those vents at the rear and you will see fan impellers integrated into the motor assembly. This is why the body is so small in size compared to the power of the motor.

An FP at stall will almost immediately destroy itself regardless of the circuit breaker used (it might survive with a 20A, but I doubt it).

Bottom line, never stall a Fisher Price motor...

Regards,

Mike

Re: Fisher Price Breaker Size
 

If you don't see the fan blades it is because you may have already melted them off. In which case this is another warning sign that you've overloaded the motor.

I wish I was joking.

-John

Re: Fisher Price Breaker Size
 

Okay I have a question about how many Fisher Price Motors we are allowed. I was under the assumption that we were allowed an unlimited amount, but now I'm not so sure.

According to this:

COTS – A “Commercial, Off-The-Shelf” COMPONENT or MECHANISM, in it’s unaltered, unmodified state. A COTS item must be a standard (i.e. not custom order) part commonly available from the VENDOR, available from a non-team source, and available to all teams for purchase.

<R51> Motors specifically permitted on 2009 FRC ROBOTS include:

A. All motors, actuators, and servos provided in the 2009 Kit Of Parts,

B. An unlimited number of COTS servos with a maximum output torque of 55 oz-in andm aximum rotational speed of 100 rpm at 6 Vdc (e.g. HITEC model HS-322HD or HS-325HB servos, as provided in the Kit Of Parts),

C. An unlimited number of FIRST Tech Challenge (FTC) servos (HITEC HS-475HB servos),

D. One or two additional 2-1/2” CIM motors (part #FR801-001 and/or M4-R0062-12) in addition to those provided in the Kit Of Parts. This means that up to four, and no more, 2-1/2” CIM motors can be used on the ROBOT.

E. COTS motors used as one-to-one replacements (i.e. identical vendor and
part number) for motors, actuators and servos provided in the 2009 Kit Of
Parts that may have failed or become inoperable.

According to R51 E. it appears that we are allowed two fisher price motors.

Am I reading this wrong? I always thought that each team could have as many fisher price motors as they wanted?

Thank you for any help you can give in clearing this up for me, and thank you for all the previous posts they helped a lot.

DavidB

Re: Fisher Price Breaker Size
 

You are allowed only two FP motors on your robot.

Re: Fisher Price Breaker Size
 

Madison is correct. If you read rule <R52>, it bans any motors except what is specifically allowed in <R51>. One-to-one replacement means that if you are got 2 motors in the KOP, and you can't put more on by some other portion of <R51>, you can only use 2 that are identical to the KOP ones.

Note: My advice on how to determine if a motor is allowed is to read <R52> first, then read <R51> to see if the motor is one of the exceptions to <R52>.

Re: Fisher Price Breaker Size
 

If you are using the 2009 KOP FP's that came attached to those big black transmissions, they have changed since last year. The new motors have a stall current of 109.410 amps. Yes, this is absurdly high for such a small motor, but that is just how amazing these things are. So, I'd say you should start with a 30, because based on your explanation of your application that seems like it will work. If you blow those, go to the 40. The motor will be just fine. The important thing is, as others have said, don't stall the FP... Even though they have a stall current near that of a CIM, if you do stall these, their internal cooling fans will not be spinning, causing the motor to overheat.

Re: Fisher Price Breaker Size
 

Can you show the data for this rating? FP motors have never been rated over 100 amps.