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I want to apologize first as I'm a beginer in electronics and my question might sound stupid.

I've started experiencing with my Arduino Uno (I love it!) and I wanted to start a project. However, I'm missing a key component and I'm not sure it even exists.

Basically, I want to create a sort of Knob that would be robotized. I want to be able to move it to a specific position (exactly like a Servo motor) but be able to manually turn the knob and that my arduino sense the difference.

I had some ideas, for example using a potentiometer with a step motor, but I'm not certain it's the best idea. I tried a regular Servo motor but I don't think they are meant to be "manually overriden" as it's really hard to do and there is no way to read the new position. Ideally, the solution has to be really precise and inexpensive.

Any suggestion would be greatly appreciated! Thank you in advance and hurray for an Electronics stack exchange site! :D

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    \$\begingroup\$ You can buy servos and similar with position coder disks which allow position to be read electronically.| You can make something like this with photodiodes - or mechanical contacts - less recommended. \$\endgroup\$
    – Russell McMahon ♦
    Dec 29, 2011 at 0:45
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    \$\begingroup\$ @RusselMcMahon - actually, a servo has a feedback element inside already, it's just that the signal from it isn't brought outside since the loop is closed inside the case. Tap into it and the remaining problem would be that the gear train is a bit long to back drive and it may be tricky to power the pot without powering the driver/motor. An intended solution would be conceptually simpler, but with a more readily over-ridden motor/gear system. \$\endgroup\$
    – Chris Stratton
    Dec 29, 2011 at 6:51
  • \$\begingroup\$ For any of you that hate when shopping questions are closed... this is a perfect example of how a question can be asked that is actually a GOOD shopping question. Keep up the good work! \$\endgroup\$
    – Kellenjb
    Dec 29, 2011 at 14:18

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What you want is a motorised slide potentiometer. These are used in top end mixing desks. When a preset is recalled from memory the sliders all move to the right position.

For example, sparkfun has this one: http://www.sparkfun.com/products/10734

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  • \$\begingroup\$ Ohhh thanks! That was kind of obvious :) I'm looking for a rotation potentiometer but I think I found some online. Thanks! \$\endgroup\$
    – Hilydrow
    Dec 28, 2011 at 23:42
  • \$\begingroup\$ I think the term is "motor potentiometer"? Check for instance bgmicro.com/motordrivendualsection100kpot.aspx \$\endgroup\$
    – Wouter van Ooijen
    Dec 29, 2011 at 8:02
  • \$\begingroup\$ Yes! I've ordered one. I can't wait to try it! \$\endgroup\$
    – Hilydrow
    Dec 29, 2011 at 21:04
  • \$\begingroup\$ Is it me or they are pretty rare? I'm trying to find a smaller one for another project but they're all pretty big! \$\endgroup\$
    – Hilydrow
    Dec 31, 2011 at 10:36
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    \$\begingroup\$ They're fairly specialised, and yes, a small one would be hard - you have to fit in the pot and the motor and the gearing belt. Not easy to do and keep the cost down. Maybe with these new-fangled nano motors they are experimenting with on a subatomic level it may be easier... ;) \$\endgroup\$
    – Majenko
    Dec 31, 2011 at 10:48

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