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Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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It would depend on where you are measuring it and how fast you want it to respond.
Coil Winding Insulation burning would probably be the first failure point in a drill motor, Plastic end-plates melting and moving the bearings around might be another, and the brushes probably start to suffer and desolder the link braid somewhere along the way.
Eventually, you'll probably reach the temperature where the magnets demagnetise (Curie point ?), but by that stage you'll probably be looking for the fire extinguisher.
Problem is, the only direct heat conduction path from the rotor is down the main shaft. Some might make it through the brushes to the end plate I suppose. Putting a temp sensor on the can means the heat has to soak through the magnets after radiating its way across the air gap, which will give it a major delay in response. By the time you were aware of anything untowards going on at the can, it would probably be too late inside.
The heat soak effect will mean that the same temperature your motor will reach after 2 minutes of normal battling would also mean extremely bad things if it was achieved after 30 seconds.
So you would probably want to place your temp sensor in contact with the main shaft (tricky, since its spinning), and perhaps also in contact with one of the terminals (might help you pickup brush temperature).
Determining exact "destruction-in-5-seconds" threshold temperatures isnt necessary or particularly useful anyway.. what are you going to do, stop driving and let them cool down while someone beats on you ?
A more useful monitoring technique would be to plot the "normal" temperature increase curve while you have a good practice push and shove about, then watch for any drastic increases above that curve during battle indicating you're not being nice to the motors.
You probably dont have time to be watching the telemetry displays though (Pit Crew ?), so an alarm if the current time/temp point exceeds the normal time-temp point on the curve by a certain margin would be easier on the driver.
No doubt at this point Jake will weigh in with an accelerometer sensor and and algorithim integrating the normal acceleration curves of your bot and comparing them with the current acceleration curves and letting you know your opponent is overweight because of your reduced maximum acceleration rate. _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
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Tue Sep 26, 2006 10:44 pm |
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