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Unread 04-12-2011, 09:02 AM
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Um, I smell Motor!
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Unexplained loss of motor power while valves work.

http://www.youtube.com/watch?v=Gu35qtup3R4

MSC elimination match.

At the end of the match, our bot, 2137 lost ability to drive our drive motors on our way to the tower to deploy the minibot.

As can be seen in video, we can still control the valves and move the arm, although it appears sluggish, which also leads me to believe that we may have lost control to the spike that powers the compressor. But being that we are controlling the valves, the problem should not be communications to the cRIO and the field, correct?

Drives are PWM controlled Jaguars, 3 gray and 1 black. 2 CIM on left, 2 CIM on right, tank drive configuration.

My thoughts were that the digital side card lost comms or had some failure. When we powered back on in the pits, everything worked, we reviewed the connections to the digital side card, both power and 37pin cable. We really never found a reason for the failure. Bot was fine for the last four matches.

Any ideas on what should be checked or replaced at Nationals?
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Unread 04-12-2011, 09:11 AM
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Re: Unexplained loss of motor power while valves work.

Digital Sidecar has metal shavings (or something else) shorting out the 5v line. When shorted (or overcurrent), the 5v supply shuts down to protect itself from destruction.

Basically every output device on the DSC requires 5v to power at least the enable circuit, so without it nothing can be enabled.

The solenoids work since they are on the solenoid bumper, which is completely separate from the digital sidecar.
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Unread 04-12-2011, 09:16 AM
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Re: Unexplained loss of motor power while valves work.

Quote:
Originally Posted by apalrd View Post
Digital Sidecar has metal shavings (or something else) shorting out the 5v line. When shorted (or overcurrent), the 5v supply shuts down to protect itself from destruction. ...
Sure looks like you lost the Sidecar. Shorting out the 5V rail is the most likely cause. Sometimes the Sidecar will protect itself when this happens, but it is also possible for ICs inside it to fail -- that happened to us at MSC. Two ICs showed pitted plastic tops, and that familiar smell of magic smoke, after we drilled through the red wire on one of our PWM cables coming from the Sidecar. Fixed the cable, replaced the Sidecar, good to go, lesson learned: don't hide cables where drills can find them!
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Unread 04-12-2011, 11:53 AM
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Um, I smell Motor!
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Re: Unexplained loss of motor power while valves work.

Thanks for the input!

So seeing we ran fine after this failure, there probably isn't a damaged component on the sidecard.

Can the sidecard be opened and cleaned out? or better to be replaced and tested?
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Unread 04-12-2011, 01:24 PM
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Re: Unexplained loss of motor power while valves work.

I'd open it and clean it out.
Test it afterwards to see if permanent damage was done, but most of the time it's shifting debris that causes temporary brownouts, but no permanent damage.

I tend to do that with all the components as they come off the robot, even if they haven't demonstrated problems.

Eveything collects metal dust at the least from rubbing gears and mechanism pieces. The bigger problems are metal filings and those aluminum spirals from drilling over unprotected electronics.
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