Chief Delphi - putting auto-reset breakers on spikes in 2012

Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Electrical (http://www.chiefdelphi.com/forums/forumdisplay.php?f=53)

- - putting auto-reset breakers on spikes in 2012 (http://www.chiefdelphi.com/forums/showthread.php?t=103286)

Re: putting auto-reset breakers on spikes in 2012

FrankJ--

The compressor is a special case, compared to something like a window motor. The compressor has high start current, but it is not really possible in an FRC robot to stall the compressor motor. It is easy to build a mechanism that can stall a window motor.

Re: putting auto-reset breakers on spikes in 2012

Frank,
We are saying that it is illegal under the current rules. This is not an opinion.

The Thomas compressor lists 25 amps as the max start current with 10.5 amps run current. The Viair compressor is listed at max current of 10 amps but I suspect start is much higher.

Re: putting auto-reset breakers on spikes in 2012

At Kettering we had auto-resets in our motor spikes before inspection, and it was questioned. I said that it was not clear in the rules, and the inspector said he would review with the head inspector and get back with me. I said I had the fuses, and we can replace, but I would like to know if it is legal, as we blow the fuses, when we jam a ball. I never had a response from the head inspector, or the original inspector. We blue all of our spare fuses and and a few from donated ones from teams after 3 matches. I put the auto resets back in to complete. I did make an effort to find an inspector, and check at the "service desk" in the pits, who could not locate one to verify, before I replaced them. The service desk did have the printed rule book, and I read the rules again, and did not where it was disallowed. I too agree that replacing the fuse with a breaker is not modifying, the manufacturer allows it, the rules recommend it for the compressor, and the one of the rules read an approved current limiting device, which the breaker is... although I could not find an approved list, it comes in the kit of parts.

I also had 3 new jags and 3 old victors on hand. I lent 2 of the jags out to other teams, 1 came back missing the magic smoke, and one never returned.... (so much for GP I guess)

I will have victors on the bot for the next competition.
Ball jammed in your conveyors with banebots motors, and drivers that jam you hair whipper motors under bridges, will eat your fuses....

I was searching here to see if there was a discussion, and there was. :)

Re: putting auto-reset breakers on spikes in 2012

At SD one of the inspectors told us that we should switch to the autoreset breakers for our motor spikes. I was confused when he told us this because I was fairly certain it was not allowed (I told my team to be ready to swap them out again), but I went ahead and did it.

Re: putting auto-reset breakers on spikes in 2012

Quote:

Originally Posted by tr6scott (Post 1140115)

The rules explicitly state:

Quote:

[R58]

The control system is designed to allow wireless control of the Robots. The Driver Station software, FirstTouch I/O module, cRIO, speed controllers, relay modules, wireless bridge, and batteries shall not be tampered with, modified, or adjusted in any way (tampering includes drilling, cutting, machining, gluing, rewiring, disassembling, etc.), with the following exceptions:

User programmable code in the cRIO may be customized.
Dip switches on the cRIO may be set.
Speed controllers may be calibrated as described in owner's manuals.
The supplied fans attached to speed controllers may be powered from the power input terminals.
The fuse on a relay feeding the compressor may be replaced with a 20 Amp Snap-Action circuit breaker (recommended).
Wires, cables, and signal lines may be connected via the standard connection points provided on the devices.
Fasteners may be used to attach the device to the Operator Console or Robot.
Labeling may be applied to indicate device purpose, connectivity, functional performance, etc.
Brake/Coast jumpers on speed controllers may be changed from their default location.
Limit switch jumpers may be removed from a Jaguar speed controller and a custom limit switch circuit may be substituted.
If CAN-bus functionality is used, the Jaguar firmware must be updated as required by FIRST (see Rule [R61]-D).
The First Touch I/O module’s firmware may be modified.
Devices may be repaired, provided the performance and specifications of the component after the repair are identical to those before the repair.

Replacing the fuse with a resetting breaker is permitted only for the compressor - otherwise, you are changing the factory conditions of the fuse and altering its performance. If you put the breaker in, you'll be able to run the fuse longer at higher voltages before that breaker trips, AND you'll be able to run it again on the field after it trips. In both cases, the performance is not identical to what it was before the change.

I can understand your frustration in blowing fuses with your motors, but take this as a learning opportunity for your team. If you look at the specs for the motors in the KoP this year (available here, the link can be found on the KoP website), you can see which motors (most of them) will draw more than 20A at stall - the stall current is listed clearly. Based on that, you can make a decision on what to use. If your motor is operating in a way that it will never stall and never pull more than 20A, go ahead and use a spike. If it could stall (like your ball collector), then avoid using a spike unless its one of the motors that doesn't draw more than 20A at stall (like the right Window motor).

Re: putting auto-reset breakers on spikes in 2012

As a general protection scheme, most motors will blow the their fuses at stall. If not their fuses then some other over current device first. For a device designed not to stall this is a good thing. The problem comes when you have a device that will stall occasionally as part of its function. The First scheme it to run it with current protection that is too high to provide it with any protection.

An exception is something like a window motor that is designed to run stalled for short period of time & they generally have some kind of thermal switch.

I do not buy the replacing the fuse with a self resetting breaker is a modification, but if you read the robot inspection sheet, it pretty well implies it is against the rules which in the end is the only thing that matters. Especially since the rules allows you to use a victor on a 40 amp breaker and completely smoke your motor. :(

Hopefully the rules committee will review this for next year & either allow a beefier relay or a self resetting breaker on the spike.

Re: putting auto-reset breakers on spikes in 2012

Everyone,
The fuse on the Spikes may be changed to a breaker for the one and only Spike that controls a compressor. No other fuses may be exchanged for breakers. The condition exists that most motors in the KOP this year are capable of much higher currents than the Spike is designed for, exclusive of stall. By changing the fuse, you violate the manufacturers specification on this part and it is possible that you would violate the warranty on the Spike. Your choice is to modify your design so that run current on the motor of your choice is less than 20 amps or change your Spike to a speed controller.
I am sorry that the LRI did not get back to you. He may have tried to get in touch with me but didn't have my phone number or asked me after the fact. In any case, your fuses musst be replaced for your next competition.
Al

Re: putting auto-reset breakers on spikes in 2012

Quote:

Originally Posted by Al Skierkiewicz (Post 1140341)

Everyone,
By changing the fuse, you violate the manufacturers specification on this part and it is possible that you would violate the warranty on the Spike.
Al

Not so sure on that, as the manufacture states here http://www.vexrobotics.com/217-0220.html

"Spike is a 20 Amp, H-Bridge Relay Module that is small enough to be remotely mounted almost anywhere on your robot. Spike is designed for driving small motors in forward, reverse, or stop (brake). Spike is opto-isolated at the signal input to protect the Robot Controller against motor noise and return currents. Requires a 3-wire cable for connection to the Robot Controller.

Ideal for 2 independent solenoids, light, pumps.
Design will accept auto-resetting circuit breaker.
Compact design"

Bold for emphasis by me.

So I would contend that using the breaker is not against the manufactures specifications. Also on that page, they sell the auto reset breakers.

We now have victors, and are very happy with the performance.

Re: putting auto-reset breakers on spikes in 2012

Scott,
The breaker reference is for the compressor only and that recommendation came from IFI years ago.

Re: putting auto-reset breakers on spikes in 2012

The short of it is that you can ask the GDC for clarification, but until then the ultimate interpretation of these rules rests with the Chief Robot Inspector. He has made his interpretation very clear in this thread and at LRI training. It is a very consistent message. FRC does not allow the use of a circuit breaker in a spike that controls a motor. If you'd like to see that changed, ask the GDC.

I know it is frustrating, but this is one of the areas that we have to be painfully conservative.

Re: putting auto-reset breakers on spikes in 2012

Incidentally, I e-mailed IFI technical support to ask if this was an acceptable configuration (in their mind). They declined to express an opinion directly, noting that since the breaker was not manufactured by them, its suitability was "out of our scope".