Arduino Motor Shaft Position Sensor Options

[kiyoshigawa]

Hey everyone, I'm working on getting a digitally controlled motor setup for the Arduino working, and have made a good deal of progress on the H-Bridge end of things (I'll post more on that once the design is finalized).

What I'm not sure of is the position sensor I'll need for this setup to work. I need a position sensor that can rotate continuously, and gives a fairly accurate reading. I also need it to take no more than one analog pin on the Arduino.

I've looked into continuous rotary potentiometers, which can be fairly pricey, and generally have rather inaccurate signals without a fair bit of filtering beforehand. I know rotary encoders are much cleaner and usually more accurate, but they can be expensive as well. I'm not sure if there are any encoders I can get to work using only one analog pin (and presumably some kind of counting chip or other interpreter chip). I've seen mention of using a two-axis hall effect sensor, but I don't know much about that either.

My question to you all is this: Are continuous rotary potentiometers the best position sensors available, or is there something better out there that will use only one analog input pin?

[bill2or3]

I think the AS5040 magnetic rotary encoder would be suitable. it's output is via a PWM dutycycle, so you could read it with one pin.

here's the chip:
http://www.austriamicrosystems.com/eng/P...ers/AS5040

and you can get a board for it here:
http://store.makerbot.com/electronics/pc...-v1-0.html
(docs here: http://reprap.org/wiki/Magnetic_Rotary_Encoder_1.0 )
The other options would be:

a quadrature encoder, but that needs more than one pin.

an optical based encoder that uses light reflecting off a wheel printed with a black-to-white gradient, but that seems prone to inaccuracies from ambient light.

If you're using several sensors perhaps you could go with an SPI interface, and get it down to 3+N wires, where N is the number of sensors.

[kiyoshigawa]

The magnetic rotary encoder looks nifty. I think I'll order a couple samples from them and see how they work first-hand. Thanks for the info.