Quote:
Originally Posted by tsaksa
Well here is my attempt at suggesting something that can be done without specialized testing equipment. Please have someone who is knowledgeable in electrical safety look these suggestions over and help you implement the tests if you chose to do something similar to this. The ideas are not tested.
Do you have any motors, Jags, or batteries that are new, or that you trust enough to use for comparison? If so, you might get some idea of how good the unknown ones perform by doing a simple side by side comparison. Set up your old robot with only one CIM motor and one Jaguar on each side. The known good ones on one side, and the ones you want to test on the other. Then drive the robot straight forward and backwards several times. If the robot tracks reasonably straight each time, the Jags and CIMs are probably working correctly at least to a first level approximation.
If the robot will not track straight you will need to find out the real cause. It could be just mechanical binding or poor alignment. Look for excess friction and also try switching sides with the motors and controllers. Also swap the motors between the controllers so that you discover if the behavior is due to the Jag or the CIM. Doing enough side by side comparisons should eventually give you some amount of confidence that there is nothing seriously wrong with these components, or help to pinpoint the damaged ones.
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Be careful when doing this... motors tend to have a forward bias. Since the motors in most FRC drive trains (there are exceptions) are placed such that one side runs forward and the other reverse in order to drive the robot forward, you end up with the two sides being slightly unbalanced. As a result, the robot will have a strong tendency to turn slightly when you try to drive it straight. The test as you described would run into this bias, and you'll likely see the robot drift to one side, making you think the motors on that side were "bad".
Here is a better test setup that any FRC team can do with items from the KoP:
Hook up a motor to a Jaguar, and into a gear box. On the other side, hook up the output shaft on something that will produce a moderate load on the motor (for example, have it lift a bucket of sand, or a concrete block) and a rotary encoder from the KoP. Control it all through the cRio. You need a moderate load on there to ensure the motor is actually working - without a load, it's a lot easier for the motor to actually do its job, and a lot harder to tell if something isn't right.
Your program should be pretty simple - spin the motor for x seconds, and record the revolutions from the encoder. Repeat a few times so you can have some consistent readings. Swap in a different motor, and do it all over again.
You'll have to record the voltage during the test and recharge the battery often - you'll see as it wears down that the characteristics of your output change, even if the motor/Jaguar stays the same.
If done right, this type of test can help provide your team with valuable insight into how all of these components work, and how they may deteriorate with time.