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Originally Posted by Yellow Eyes
We're trying to get some feedback on the various motions our robot's arm can make and two of them use the 100K 10 turn pots (Bourns 3590s). One of them is returning what seems to be fairly normal values to the RC (for rotating the arm), but the other (for extending the arm) just sits at max (255 with a bit shift, 1023 without) no matter where you turn it until about 1/8 to 1/4 of a turn from the end when it suddenly sinks all the way down. When tested on a multimeter though, the values are normal, 0 to about 100K ohms. The 2 pots are connected to rc_ana_in02 (extending) and rc_ana_in12 (rotating). If we swap them, rotating continues to work, and extending continues to just sit at max. Has anyone ever come across this before? Or does anyone know any potential fixes?
Thanks ahead.
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It gives every indication of a bad connection to ground. The pot will always exhibit open circuit voltage i.e. 5 volts, until the lower side of the pot is attached to ground or the wiper is no longer contacting the element. The fact that numbers change near the end of the final turn may indicate that the wiper is no longer contacting the resistive element. Try running a test wire from the battery "-" terminal on the breaker panel to the lower pin on the pot and see what happens. (or measure the pot elements from the connector that plugs into the RC.) It should measure normal and when power is applied it should vary between +5 and 0 volts.