Question from a ROOKIE Team

[operationpeacce]

We have been having some problems with our Jaguar Motors. The problems started when one of our four motors refused to work. We tried to replace the PWM cables and nothing.... Next, we tried to change its port, NOTHING.... Finally, we just replaced it and the new one works fine. We would have been all set except the same thing happend to the Jaguar right next to it. We don't know what is wrong.. Have any suggestions?

[Matt Krass]

Originally Posted by operationpeacce

We have been having some problems with our Jaguar Motors. The problems started when one of our four motors refused to work. We tried to replace the PWM cables and nothing.... Next, we tried to change its port, NOTHING.... Finally, we just replaced it and the new one works fine. We would have been all set except the same thing happend to the Jaguar right next to it. We don't know what is wrong.. Have any suggestions?

We're gonna need some more details.

What motors were they driving? How exactly did they stop working? What were the lights doing? Are your limit switch jumpers in place?

I'd suspect metal shavings or something similar if two devices in proximity suddenly stop working. Clean the Jags out with some compressed air, thoroughly.

Matt

[operationpeacce]

Yes we did clean out the bot with a vacuum ( we were having a similar problem before) but nothing happened. Also, if this can help find an answer, the Jaguar light was blinking red.
Our Jaguars are controling Sim driving motors.

[operationpeacce]

Any suggestions?

[DonRotolo]

A vacuum is not going to remove much of the metal shavings that I suspect are in the Jaguar. And, as a rookie team, I can understand how you might not understand how very important it is to keep even the tiniest bits of metal out of the Jaguars. Failing to do so will be a costly lesson in a very short time.

Take the failed jaguar(s) and open them. They're trash anyway. If you find the tiniest speck of metal in there, that is the reason they failed.

I cannot emphasize this enough: ALL metal shavings/filings/dust/particles MUST be kept out of ALL the electronics, or failures will happen with increasing frequency.

Compressed air is the only way to remove this, and even then it's only partly effective. You must find a fool-proof way of keeping all electrical parts completely free of metal dust.

[Matt Krass]

Originally Posted by DonRotolo

A vacuum is not going to remove much of the metal shavings that I suspect are in the Jaguar. And, as a rookie team, I can understand how you might not understand how very important it is to keep even the tiniest bits of metal out of the Jaguars. Failing to do so will be a costly lesson in a very short time.

Take the failed jaguar(s) and open them. They're trash anyway. If you find the tiniest speck of metal in there, that is the reason they failed.

I cannot emphasize this enough: ALL metal shavings/filings/dust/particles MUST be kept out of ALL the electronics, or failures will happen with increasing frequency.

Compressed air is the only way to remove this, and even then it's only partly effective. You must find a fool-proof way of keeping all electrical parts completely free of metal dust.

I agree that you should try compressed air, and I stand by the theory of metal shavings, but you can try hitting it from every angle with a copious amount of compressed air, through all the vents before you open them up and make them competition illegal. At least give it a shot, it won't hurt them to try.

Matt

[2611.Shooter]

our team has found a couple of ways to keep our jaguars free of shavings. 1. use quick disconnect wiring, so if you have to drill, you can remove the jag. 2. mount the jaguars on the underside of a metal plate. 3. have the entire electronics board removable, so it can be moved away from those nasty metal shavings. any one of these will work, but also check that you are not just overloading the jags! if you were reversing direction frequently (full forward- full reverse) it may burn out the motor/jag/trip circuit breaker. if so, when you open the jag you will not find shavings. just calm down with the driving then! or program in a max delta V for the drivetrain, it can be kind of difficult though. good luck with keeping the rest in working order, hope this helps!

[DavidGitz]

Originally Posted by operationpeacce

Yes we did clean out the bot with a vacuum ( we were having a similar problem before) but nothing happened. Also, if this can help find an answer, the Jaguar light was blinking red.
Our Jaguars are controling Sim driving motors.

If they are blinking red that means the following:
a) The Jaguar is powered, so "probably" not a debris issue. Although the advice given above about making sure debris doesn't get anywhere is fantastic.
b) The Jaguar is getting a signal, so it is not a PWM cable issue.
c) The Jaguar is responding to your commands.
So from what I can tell, with no other pictures or other comments, is that the problem will be in the neighborhood of the motor outputs from the Jaguar to your CIM Motor. With your motor disconnected (for safety reasons) and you move your joystick full range (to get the led blinking red/green) measure the motor output of the Jaguar. This should be around +/- 12V, based on your joystick. If this is good the Jaguar is (almost) certainly working fine, I would make sure the crimps are still good (a bad crimp will turn into no connection between the wire and the Jaguar, which exactly surfaces as the problem you've described. I've seen this a lot.) If your connections are fine then "hotwire" your motor (please exercise safety) to make sure the motor is working fine.

Good troubleshooting involves working in an organized manner, start from one side that is known to be working and work your way to the other. "Swaptronics" only works when you have narrowed the problem down to one device, otherwise it's just guessing.

Check here for information about the diagnostic lights and usage of the Jaguar Speed Controller:
http://www.luminarymicro.com/jaguar

[Matt Krass]

Originally Posted by DavidGitz

If they are blinking red that means the following:
a) The Jaguar is powered, so "probably" not a debris issue. Although the advice given above about making sure debris doesn't get anywhere is fantastic

That depends entirely on if it's a fast blink or a slow blink (am I the only one who dislikes different conditions being differentiated by blink rate? Though I suppose it would be better if we had a less subjective scale than "fast" and "slow")

If it's a fast blink, then you're probably not looking at debris, it's trying to drive the motor in reverse. You should only get this trying to drive in one direction.

If it's a slow blink, you're almost certainly looking at debris, the question is whether or not it is causing a transient problem or if your FETs have already fried.

Originally Posted by DavidGitz

If your connections are fine then "hotwire" your motor (please exercise safety)

This statement is an oxymoron.

Hotwiring motors is not a safe proposition, no matter how steady your hands are. There is a reason FIRST has us use circuit breakers and reliable connections, and it's not to cost people money or time, it's a SAFETY FEATURE.

I'm getting really sick of people advocating unsafe practices around here.

Matt

[DavidGitz]

Originally Posted by Matt Krass

If it's a slow blink, you're almost certainly looking at debris, the question is whether or not it is causing a transient problem or if your FETs have already fried.

I have never seen the "slow blink" due to a debris problem. If there has been a debris issue it almost always causes instant failure of a Jaguar. From the document that I referenced earlier:
"Fault Conditions
A slow flashing Red LED indicates that the MDL-BDC detected one of the following fault conditions:
�� Power supply under-voltage
�� Over temperature
�� Over current
�� Limit switch activated in the current direction of motion
When a fault condition occurs, the motor shuts down and the LED indicates a fault state during the
fault condition and for 3 seconds after the fault cause is cleared (except for the limit switch fault,
which is cleared instantly). A slow flashing Yellow LED indicates that the MDL-BDC is not receiving a
valid control signal."

Originally Posted by Matt Krass

This statement is an oxymoron.
Hotwiring motors is not a safe proposition, no matter how steady your hands are. There is a reason FIRST has us use circuit breakers and reliable connections, and it's not to cost people money or time, it's a SAFETY FEATURE.

I'm sure there are many different ways someone could "hotwire" a motor. What I was referring to above (and why I put in the words "please exercise safety") is to use common sense*. I can think of several ways to "hotwire" a motor without having to have a "steady hands" requirement, such as:
-If the motor is not installed on a robot, put it on a table and clamp it down.
-Use a circuit breaker inline with the power connection. All Circuit Breakers that attach to the PD Board are compatible with a standard female 12 AWG connector.

Can anyone else think of some ways to safely "hotwire" a motor?

[Al Skierkiewicz]

Not to offend anyone, but I rarely recommend compressed air unless you really know the consequences. In the Jags, air can force debris down into the plastic spacer that surrounds the FETs or it will jam the debris between component leads. On Victors, it may force it into the space between FET leads. If you use it near or in moving parts, it can force the debris into bearings or into fans and motors. If you can see debris and a vacuum can't remove it, try taking a piece of duct tape, wrapped sticky side out, to stick remove the offending material. Please remember that the Victor and Jag fans blow down onto the FETs. Any debris on the top of the fan will end up where you don't want it. Remember that open frame gears can and will throw metal dust/flakes during operation.

[wireties]

It is too late now I reckon. But in the future simple cover the Jaguars with saran wrap (or something that will created a sealed barrier) when creating metal dust or shavings in the vicinity. Do the same for the sidecar, the cRio, Spikes etc.

Remove the barrier before turning them back on again ;o).

HTH

[Matt Krass]

Originally Posted by DavidGitz

I have never seen the "slow blink" due to a debris problem. If there has been a debris issue it almost always causes instant failure of a Jaguar.

It really depends where the chips land, generally the overcurrent fault in the Jag has caught most of the problems I've seen with chips, and shut down the unit before damage was incurred. It is certainly possible though that the debris could cause a permanent failure, in fact I have one Jaguar on my desk I suspect may be a victim of such a failure

Originally Posted by DavidGitz

I'm sure there are many different ways someone could "hotwire" a motor. What I was referring to above (and why I put in the words "please exercise safety") is to use common sense*. I can think of several ways to "hotwire" a motor without having to have a "steady hands" requirement, such as:
-If the motor is not installed on a robot, put it on a table and clamp it down.
-Use a circuit breaker inline with the power connection. All Circuit Breakers that attach to the PD Board are compatible with a standard female 12 AWG connector.

Can anyone else think of some ways to safely "hotwire" a motor?

The problem was you didn't specify any of these suggestions, you simply suggested 'hotwiring' the motor (the fact that you had to use quotes around the word would indicate you knew it was up for interpretation) and the most common, especially amongst rookie teams, interpretation I've seen for hotwiring is sticking the motor wires straight in to the battery side AMP connector, and similar things like that.

What you've described here (clamps, PD board, etc) is actually a very good idea I would recommend all teams try just to have experience testing motors that way, but I wouldn't ever consider this hotwiring, instead I'd call it a test rig, or something equally less scary sounding.

My post was not meant as an attack towards you, I just know students sometimes gloss over the rest of the content available to them once they think they have a workable solution and I was afraid a student may have seen your post and tried what I described and gotten hurt or damaged something before anyone could clarify what you meant.

[DonRotolo]

Originally Posted by Al Skierkiewicz

Not to offend anyone, but I rarely recommend compressed air unless you really know the consequences.

No offense taken.

As I mentioned, compressed air is only partly effective. Vacuum cleaners have a nasty habit (at least here in the cold North) of generating static electricity, and thus are usually contraindicated for cleaning electronics.

Duct tape is cool though.

The best chance is to prevent the problem in the first place by keeping the "mechanical men" with their "stone knives and axes" away from your electronics.

[Al Skierkiewicz]

Please note the Team Update 11 modifies this discussion.
<R55>
… M. Devices may be repaired, provided the performance and specifications of the component after the repair are identical to those before the repair.

I read that as opening a Jaguar to clean out debris in the hopes of clearing a fault or rendering a repair is now legal.