Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: D1g1talDragon on January 04, 2009, 05:24:52 PM
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I'm really getting frustrated with the sensitivity of the internal potentiometer in the HiTec HS-311s. It seems like if you breathe on them wrong, they adjust off of the 90 degree mark when modifying for 360 degree rotation. This seems to include things like drying glue, low battery voltage, and solar flares. Others seem to have used fixed 2.2k-3.3k resistors in place of the pot, but even after meticulously choosing from a large pool of resistors to find two within .01 tolerance, I keep having issues getting the motor to a full stop, i.e jittering and the "zero" point being closer to 110 degrees, etc.
My question is, has anyone tried using a small multi-turn pot for this to improve the stopping resolution? I'd figure something like http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=3299P-502LF-ND (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=3299P-502LF-ND) should do the trick. It's small enough to fit in there fine, and a 5k pot should get me 2.5k on each side, which looks like it should work as far as I can see. The added bonus is later adjustment too I guess, if I were to move to a different voltage source or something that would throw the servo out of whack (or so I'm told). Sound feasible?
Still learning, thanks guys!
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My question is, has anyone tried using a small multi-turn pot for this to improve the stopping resolution? I'd figure something like http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=3299P-502LF-ND (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=3299P-502LF-ND) should do the trick. It's small enough to fit in there fine, and a 5k pot should get me 2.5k on each side, which looks like it should work as far as I can see. The added bonus is later adjustment too I guess, if I were to move to a different voltage source or something that would throw the servo out of whack (or so I'm told). Sound feasible?
Still learning, thanks guys!
That is the best solution to a modified servo. Drill a hole on the side of the servo to be able to adjust the pot latter.
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It doesn't really matter if it's not perfectly still. Just get it close enough in the center, then modify the software servo PWM to tweak it perfectly.