HELP! Cow Town ThrowDown Partcipation in Jeopardy!

[Michael Blake]

OF COURSE... "Murphy's Law" for a rookie team...

Our Victors controlling our arm rise/fall have suddenly stopped being Enabled... we use a PWM splitter from Slot 5 on the Digital Sidecar to command the two Victors that each spin a Window Motor that are combined to move a gear box...

Everything was working fine, has been working fine, until a team member pulled the PWM connector (from the Y-side) out of one of the two Victors (connected by the PWM Y-splitter) while they were ENABLED...

We have swapped out new cables... but here's the scratch-your-head part, we have five other Victors that work fine (4 CIMS, 1 bane bots gripper motor) and they enable just fine from their respective slots on the DS and when we move the new cable over to these Victors to test, they will SOMETIMES Enable and other times NOT Enable?!!

Where's the "flakiness" coming from? We've swapped-out the DS with a new one and have the same problem...

Could there be a voltage/amperage problem that causes DS "flakiness"? We get the MOST "flakiness" from when the PWM Y-splitter is attached from one DS slot to TWO Victors?!

IF we can't resolve this... I can't see how we can justify driving 14 hours each way from San Antonio to Kansas City...

THANK YOU in advance for help!

[Billfred]

Two questions:

1) Have you removed the locking pins from your window motors? That can cause everything to bind up, causing some things to work one way but not others.
2) Are you sure you're not getting 12V from the Victor outputs? (It's not stated in the original post, so I figure it's worth asking. If you are, I bet it's the locking pins from above.)

[Michael Blake]

Originally Posted by Billfred

Two questions:

1) Have you removed the locking pins from your window motors? That can cause everything to bind up, causing some things to work one way but not others.
2) Are you sure you're not getting 12V from the Victor outputs? (It's not stated in the original post, so I figure it's worth asking. If you are, I bet it's the locking pins from above.)

It's not the Windows Motors as we have the same problem whether they're connected or not...

We can't get the TWO Victors that drive the TWO Windows Motors to ENABLE... BOTH Victors are connected to Slot 5 in the DS via PWM Y-splitter...

[baronep]

First, determine if the problem is with the PWM or with the Victors. Put the robot up on blocks and swap a PWM from a working Jag and move it to one of the questionable ones, if the victor works, your PWM is the problem. Otherwise, your victor is the problem and might need to be replaced. I would venture to say that more likely though, the PWM is the problem. The PWM connections on the Victors are kind of finicky. I find myself needing to unplug and replug the PWM several times to get it to work. Also, make sure that the PWM is pushed in all the way and not resting on a pin that is out of alignment. All of these would cause the victor to not receive a signal from the cRIO and not work.

Hope you get it fixed,

Patrick

[Michael Blake]

Originally Posted by baronep

First, determine if the problem is with the PWM or with the Victors. Put the robot up on blocks and swap a PWM from a working Jag and move it to one of the questionable ones, if the victor works, your PWM is the problem. Otherwise, your victor is the problem and might need to be replaced. I would venture to say that more likely though, the PWM is the problem. The PWM connections on the Victors are kind of finicky. I find myself needing to unplug and replug the PWM several times to get it to work. Also, make sure that the PWM is pushed in all the way and not resting on a pin that is out of alignment. All of these would cause the victor to not receive a signal from the cRIO and not work.

Hope you get it fixed,

Patrick

We have tried switching the PWM from the windows motor Victors that aren't working with two of the CIM motor Victors and it is still not ENABLING consistently. Everything seems to be pushed in correctly, and we have, over the course of troubleshooting the problem, unplugged and replugged the PWM dozens of times. We are still getting a "flaky" voltage readout after all of these things.

The "flaky" readout is from the tip of the PWM, not the DS.

[baronep]

Just for the hell of it, try checking the voltage between your frame and any of the negative ports on your PD board. We had a problem last season where we were discharging voltage onto the frame and that F'ed all of the electronics up.

[Michael Blake]

Originally Posted by baronep

Just for the hell of it, try checking the voltage between your frame and any of the negative ports on your PD board. We had a problem last season where we were discharging voltage onto the frame and that F'ed all of the electronics up.

The PD isn't in contact with the frame and shouldn't be discharging.

[baronep]

I would try unplugging everything, from the cRIO to the motor and try brand new components where you can and hopefully in reassembling them you will fix the problem. It also is possible that you have multiple faulty PWM cables. I don't know why but it always seems that we have more that don't work than do work. Also, with the blinking light on the victor, it doesn't change color or pattern when you ENABLE/DISABLE the robot from the driver station right? If it does, it means that the PWM is not the problem, but overcurrenting or something else is going on.

[Michael Blake]

Originally Posted by baronep

I would try unplugging everything, from the cRIO to the motor and try brand new components where you can and hopefully in reassembling them you will fix the problem. It also is possible that you have multiple faulty PWM cables. I don't know why but it always seems that we have more that don't work than do work. Also, with the blinking light on the victor, it doesn't change color or pattern when you ENABLE/DISABLE the robot from the driver station right? If it does, it means that the PWM is not the problem, but overcurrenting or something else is going on.

The blinking light on the Victor doesn't change color or pattern when we ENABLE/DISABLE the robot, it blinks at the same rate. However, we did rewire and put together a seperate PD and when we ENABLED the Victors that were plugged into it, they briefly turn red when we ENABLE.

As for your first idea of unplugging and putting in brand new components, we are planning on doing this as a last resort if we cannot troubleshoot and eliminate the problem.

[blturner]

Look for grounding problems. If you leave out the ground lines to the DSC the PWM can become flaky. I had a team that left off the ground lines because they were not using any power on the DSC. Turns out you need them anyway.

[James Tonthat]

I also posted on your FB wall. Let me know if you're still having problems, I can probably drive down there Thursday if you need the help or possibly late Wednesday.

[Alan Anderson]

Originally Posted by Michael Blake

Everything seems to be pushed in correctly,...

When dealing with Victors and PWM cables, "seems to be" isn't good enough. Occasionally you need someone with years of experience to be able to tell that something literally doesn't feel right, and to apply the proper subtle touch to get the connector to seat properly.

That's the one thing about Victors I don't miss when using Jaguars instead.

[Al Skierkiewicz]

Michael,
While the buffers on the DSC should be able to handle the removal of a PWM cable it is entirely possible that in trying to reinsert the cable a voltage was conducted backward into the DSC. The PWM cable does carry +5 volts and power common. The +5 volts is used to power the opto-couplers inside the Victors. My first recommendation is to find a new PWM cable and connect it in place of the PWM wiring currently on the robot. If the Victor then enables, you can guess that the 'y' cable or the PWM cables are at fault. If the Victor does not not enable as before, try connecting to a know good Victor. It is unlikely that the Victor could be damaged by pulling out the connector but it possible. I am guessing that you have checked that the PWM cable is fully inserted. These connectors do require some experience to get them fully into the connector body on the Victor. When fully inserted, 1/8" or less of the brown PWM connector is visible above the case of the Victor. Hope this helps. I would bet that the trip would not be in vain as other teams are sure to help you when you arrive.
Al

[Michael Blake]

Al,

We have replaced the PWM cables several times (including the Y-splitter), and we are still getting "flaky results". We also replaced the Victor and the DS, as said before. The PWM cable has been confirmed to be in there. So what we have basically done is confirmed that the PWM cable and the Victor itself is not at fault, and the PWM is fully inserted into the Victor.

We aren't sure what is left to troubleshoot at this point; we believe we have narrowed down the problem to either the PWM connected to the DS or the Victor, as when we checked the voltage from the tip of the PWM, it was fluctuating every time.

[JackS]

Originally Posted by Michael Blake

when we checked the voltage from the tip of the PWM, it was fluctuating every time.

We experienced a similar problem at WPI this year. The problem disappeared when we re-imaged the cRIO to V29, even though we weren't using CAN. We never made any further inquiries into the problem, so I can't verify the validity of that fix. Regardless, I would try making sure the firmware on the cRIO is properly imaged. It doesn't hurt.

Jack