Grey Jaguar No Power Out

[ajlapp]

I left this unresolved for now......I grabbed another Jaguar in the meantime.

I suspect that I will find shavings inside at some point.

Thanks for the help. I was able to get the machine up and running with no problems.

[Tom Line]

Originally Posted by ajlapp

I left this unresolved for now......I grabbed another Jaguar in the meantime.

I suspect that I will find shavings inside at some point.

Thanks for the help. I was able to get the machine up and running with no problems.

Anthony, once upon a time the folks who make the Jaguars were excepting returns for troubleshooting. You may want to contact them (you can find them in a more than a couple threads) and see if they're still taking return / swaps. You might get lucky and get it replaced for free.

[Ether]

Originally Posted by Tom Line

You may want to contact them ... and see if they're still taking return / swaps. You might get lucky and get it replaced for free.

As the old saying goes: "If you don't ask the question, the answer is NO"

[ajlapp]

Good thinking....I'll ask.

Though I read in the manual explicit instructions not to completely remove the terminal screws.

I see they changed that with the Black Jaguars.

[dbeckwith]

My team was having this exact same problem, thanks for all the possible problems to try. We ended up getting another Jag anyway, but if we can fix our broken one then at least we have a backup.
I know we've unscrewed the terminal screws several times, so we could have shavings. I don't think it's the program or jumpers, I've checked those, and I think I would have noticed if the current sense circuit was unsoldered when we opened the Jag. I saw something in the Jag manual about calibrating the PWM signal, so I might try that. It could also be one of the MOSFETs. Anyone know a way of testing if any are blown and/or how to replace a broken one?

[Al Skierkiewicz]

Daniel,
The current sense resistor might not grab your attention if is missing. This was the case in some of the devices I inspected. Generally, when a FET goes bad, it leaves a burned area around it. The plastic FET retainer/insulator will be melted and there will be black marks on the board as well as burned circuit board traces. If the FET is open, you can measure with a VOM. Use the diode test position on your meter if it has one. In general with a failed FET gate driver, there is no visual damage. However, on several I have examined, the FEET driver chip had blown apart one corner and left a crated on the board.

[dbeckwith]

I can't see that any of these problems are what's wrong with our Jag. The only visible thing I see that's different with the diagram in the manual is an extra resistor connecting R25 and R24, right under the current sense resistor. All our Jags seems to have it. The color bands go gold, yellow, purple, yellow. I realized also that the one we have that isn't working is one of the four we got in the rookie kit last year but have never used until now, so it's actually never worked, but all the others have. Is that resistor supposed to be there?

[Al Skierkiewicz]

Daniel,
The resistor is read the other way indicating it is a 470K (yellow, violet, yellow) while the gold band indicates 5%. In the schematic it is the bias resistor for the current sense amp, R43. This resistor centers the opamp operating voltage so that it varies around a quiescent 3.3v/2. When you try to use your Jag what is the color of the LED telling you?

[dbeckwith]

Originally Posted by Al Skierkiewicz

When you try to use your Jag what is the color of the LED telling you?

The lights read as if the Jag were operating normally: medium flashing green when forward, solid orange when stopped, and medium flashing red when backward.
Actually, while typing that I thought of something! The Jags are supposed to show solid green when fully forward and solid red when fully backward, but even when I push the joystick all the way, it never goes solid. When we tested the voltage coming out of the Jag, we just got negligible voltage and assumed it was nothing, but maybe for some reason the speeds are getting scaled down by 50 or something. I'll try to look into why that would be.
That seems the most likely reason for our trouble now, since I couldn't find anything else wrong with the Jag. The manual said: "To accommodate variation in the timing of the supplied signal, the MDL-BDC has a calibrate feature that sets new values for full-forward, full-reverse, and points in between. Calibration is typically only required in applications where the PWM source has uncertainties due to analog radio links or other variables. Direct digital sources are unlikely to require calibration." This might be one of those "unlikely" times.
So that might be it. Al least it's now the primary suspect, and secondary would be the code.

[jhersh]

Originally Posted by dbeckwith

That seems the most likely reason for our trouble now, since I couldn't find anything else wrong with the Jag. The manual said: "To accommodate variation in the timing of the supplied signal, the MDL-BDC has a calibrate feature that sets new values for full-forward, full-reverse, and points in between. Calibration is typically only required in applications where the PWM source has uncertainties due to analog radio links or other variables. Direct digital sources are unlikely to require calibration." This might be one of those "unlikely" times.
So that might be it. Al least it's now the primary suspect, and secondary would be the code.

If you are using a cRIO with WPILib to control your Jag over PWM, you should not need to calibrate it. They were designed to operate together out of the box. Do make sure that you haven't told WPILib that you are using a Victor instead of a Jaguar, though.

[Al Skierkiewicz]

Daniel,
The lights indicate that you are not going to full throttle in each direction but that is usually the case. If the control fault is not software related, Jag calibration will match your controller to the full output of your joysticks.
If you are only testing the output of the Jag with a voltmeter, remember that the Jag output switching frequency is 15kHz which is way above the frequency limits for many voltmeters. They are also not intended to read PWM, square wave signals. The Victors are 150 Hz which is in the range for most meters but are still not accurate due to the square wave output of motor controllers.

[Ether]

I would think an analog voltmeter on the "DC" setting would do a reasonable job of measuring the effective DC-equivalent voltage of the Jag's PWM output.

Haven't actually tried it though. Anybody got data ?

[Vikesrock]

^Reported

[Mark McLeod]

I tested with a globe motor load and the oddity disappears, so the odd collapsing waveform and the 2v drop seems to just be a characteristic of the adaptive gate Al brought up and the lack of a load as Alan suggested. It shouldn't affect normal operation.
There was a .15v drop through the Jag at 100%, but my battery is down a bit so that's not a full measurement.

The gray/tan jag gives full power at 100% with a load, and 2v less without a load.

With a load the waveform is the typical duty cycle switching between 0 and battery voltage for increasingly longer times as the throttle changes.

The CIM and the window motors show a cleaner 100% than the globe motor for some reason. Up to 100% everything about the power output waveform is identical. At 100% I see the periodic tiny drop to 0v on the CIM and Window motors, but for the globe the scope displays a messier plot.
The CIM also drew the battery down a bit more than the others of course.

[Ether]

Originally Posted by Mark McLeod

With a load the waveform is the typical duty cycle switching between 0 and battery voltage for increasingly longer times as the throttle changes.

Did you observe this behavior in both the Tan and Black Jags, or the Tan Jag only?

I ask because Gdeaver reported in an earlier post that the Black Jags use locked anti-phase switching.