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View Full Version : [Question(s)] Help finding servo potentiometers



alonso
06-21-2013, 07:00 PM
I'm looking for a servo potentiometer and I can't seem to find anything remotely close to it on Mouser or DigiKey. Those website are nebulous and packed dense with information. Could someone point me the right direction??

I'm looking for a potentiometer with the smallest dimension down the axis of the shaft, the diameter or width height is not too important.

The application is to use it as a rotary sensor. I could purchase cheap servos and rip it out of them, but that just seems wasteful.


https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTqVeB99fG9hV0UUD9RYbkHlYgHlAhnh foEZx_H9gh5ziEQKj7a

Thanks!!!

-Alonso

Th232
06-21-2013, 10:01 PM
Would you be willing to consider an encoder instead of a pot?

tician
06-21-2013, 10:38 PM
Digikey -> Sensors, Transducers -> Position Sensors - Angle, Linear Position Measuring
All angular and rotary sensor types.

jwatte
06-22-2013, 12:05 AM
If you absolutely need a potentiometer, you could try a "trimmer" which has no shaft, just a cross in the center of the wiper.
However, if the point is to sense position, I would highly recommend using some kind of optical or magnetic absolute encoder.
And if the point is to sense velocity, a quadrature encoder (optical or Hall) would be sufficient.

Th232
06-22-2013, 12:39 AM
A trimmer could be an option, but if you do go with one be aware that they usually have very short rotational lifespans since they're normally meant to be set then never adjusted again.

alonso
06-22-2013, 01:26 PM
I actually purchased trimmer pots from DigiKey only to find out that like Th232 said the life cycle for most of them were 500 turns...

I have thought about using a magnetic rotary encoder, but it sounded like more complex electronics that I've done so far, but it might be a good project to learn this stuff.

I found AtonB's servo hack's tutorials and although it seems that his www.01mech.com (http://www.01mech.com/) website is down, I found these files:

https://code.google.com/p/zosupermodified/

I don't know how to use Eagle schematics software but I'm going to start by looking into CadSoft Eagle. Is this a good software to use?

tician
06-22-2013, 01:58 PM
Eagle is pretty nice, but very expensive if you need more layers or larger boards than the 'freeware' version permits. I have not really been doing much pcb design recently, so I have not had the incentive to change over to Kicad or gEDA.

For some reason I remember the AX-12+ encoder being blue (http://www.digikey.com/product-detail/en/SV01A103AEA01B00/490-2400-ND/588421), but that may just be my brain making up more crap. I bought a couple of these (http://www.digikey.com/product-detail/en/EM3242/974-1044-1-ND/2695032) for the laser range finder that I never finished and never got a chance to make a board for them. All you are supposed to need is a 3V regulator, a couple decoupling capacitors, and an ADC pin on your microcontroller.

jwatte
06-22-2013, 06:20 PM
You can buy ready-made optical encoders that can mount straight to a shaft. There's typically a "reader" part and a "disc" part.
The main concern there would be size -- I'm not sure you can get off-the-shelf miniature parts -- and perhaps price, if you're very price sensitive.