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#1
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powr dist. board/cRIO puzzle - please advise!
In our second quarterfinal match yesterday, our robot went over the bump and upon hitting the ground on opposite side, the cRIO cut out and we were dead on the field. Back to the pit, tethered up and could not recreate the problem. Out to the field and the first bump to the robot and it went out again, then rebooted after time, the cut out again.
Troubleshooting afterward (haing won the first match, we lost the second two), we found that if we pulled one specific fuse to one of our window motors, the cRIO problem was gone - we could smack the robot into walls, shove it, bounce it up and down, etc and no problem. We put the fuse back in... and simply picking one end of the robot up a couple inches and dropping it caused the failure to occur. I'd appreciate your good minds on this one, and thanks! |
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#2
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Re: powr dist. board/cRIO puzzle - please advise!
I'll take a guess that either the motor or the wiring to it have an intermitant short to the chassis.
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#3
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Re: powr dist. board/cRIO puzzle - please advise!
The internal contacts inside the window motor may have come loose and touch the frame of the motor every time your robot goes over the hump. I would try switching the motor and see if you can recreate the problem. If the problem still occurs then it may be that the wires feeding the motor are touching due to movement.
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#4
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Re: powr dist. board/cRIO puzzle - please advise!
This isn't going to help much, but it shouldn't matter if the motor is shorting to the frame. The cRio and the camera should be insulated from the frame.
Check the resistance from both the positive and negative terminals of power distribution board to the frame. The resistance should be really high or at infinity if everything is properly insulated, preferably infinity... but moisture can cause some the resistance to go lower. This is exactly one of the reasons why everything is supposed to be insulated from the frame. If you find the resistance to be near zero or at zero, then you definitely have a grounding problem. Start pulling fuses and ground wires until you find which one is causing it (Hint: Try the cRio and camera first). Last edited by RyanN : 28-03-2010 at 12:42. |
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#5
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Re: powr dist. board/cRIO puzzle - please advise!
You could also be suffering from metal chip(s) inside your PDB, near the area where that fuse is located. It doesn't hurt to vacuum out your electronics too, and try not to drill over top of them.
-Nick |
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#6
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Re: powr dist. board/cRIO puzzle - please advise!
If you are using the WET610N wireless bridge, check how your power plug fits into it. It's really loose on all the models I've played with, which is why its relegated to our practice bot. If you don't have the older bridge on hand, try some hot glue.
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#7
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Re: powr dist. board/cRIO puzzle - please advise!
Steve,
You need to check everything following the breaker that feeds the window motor. You could have a bad speed controller, intermittent connection at the input or output of the controller or the motor itself. In some cases, a short in any of the input wiring to the frame of the robot can find it's way back to the Crio especially during hard robot frame hits. In some cases this causes a Crio reboot. You know how long that can take. You also may lose handshake with the wireless adapter. Could you see the RSL and can you tell us what the flash rate was during the outage? The most sensitive wiring that could cause these faults are power wiring to the Crio, loose hardware on a controller, power wiring on the window motor, and power wiring on the DSC. I am going to bet that the two input connections on a speed controller are very close together. These touch with robot movements. |
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#8
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Re: powr dist. board/cRIO puzzle - please advise!
we too had the problem of everything shutting off while going over the bump. We determined it to be electrical interference from the wireless bridge or a bad main breaker. either way, after replacing the main breaker, and moving/replacing the wireless bridge, the problem was gone.
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#9
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Re: powr dist. board/cRIO puzzle - please advise!
Thanks to everyone who has written so far with ideas. Unfortunately, we had to pack the robot into a shipping crate and off to ATL so didn;t have time to do as much as we would have liked. Trying to put together a protocol for when we get there to diagnose and correct as quickly as possible. I will ask the mentor who knows the most about all of this to jump on in to this discussion as time permits, and thanks for the help - keep the ideas coming!
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#10
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Re: powr dist. board/cRIO puzzle - please advise!
Quote:
If the robot was in the shop and you were able to spend some time with it, i would probably provide a nice list of trouble shooting steps here to help. however, you aren't, and you probably don't want to have to spend a lot of time with this in Atlanta. So i would recommend one simple thing: Replace everything on that branch circuit (wiring, speed controller, motor). You can have it all prepared and ready to go before you even show up, and just swap it all out. If possible, i would also change which ports you're using on the power distribution board, just in case the problem is there. Two years ago we had to do something similar between our first and second competitions. getting everything ready ahead of time made swapping things out a lot faster. Cut all the wire longer than you need - you can just wrap it up inside the robot somewhere. |
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#11
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Re: powr dist. board/cRIO puzzle - please advise!
Steve,
If you don't find something quickly, please come and get an inspector to help you check it over. We may see something obvious that you don't. Little problems get to be big problems by about 10 AM on Thursday. |
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#12
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Re: powr dist. board/cRIO puzzle - please advise!
I third Al.
You are shorting through the chassis, through the cRIO's ground return and blowing the internal breaker on the PD. This means you have two problems: 1) Your cRIO is not isolated from the robot frame. 2) That window motor branch is not properly insulated / isolated. Fix both! |
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#13
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Re: powr dist. board/cRIO puzzle - please advise!
I'll let Chad Spackman, wjo is really the brains behind this add in when he can, but today he wired up a bench system - battery to distribution panel to victor. Shorting a 15 amp fuse on the power distribution panel immediately shuts down the cRIO,just like we saw on our robot. On this nech system, no possibility of CRIO being in contact with metal frame, no possibility of wiring gluitches with victors, etc. A simple short to the power distribution board and the cRIO folds.
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