Hello, you need not to precision, but a servo arm actuating a button for each round would be enough? It would require a pulse counter ARC to add or subtract from a starting position. For more precision servo arm star (4 arms) that are 4 pulses per revolution. There are also square odometers, more complex and precise. Greetings and I hope that helps you some idea.

rotary encoder

If anyone cares I found the answer. I put a 10K resistor across the +5V and the signal from the Hall effect and the ADC now goes form +5V to 0 when the magnet is in proximity of the Hall IC.

Hi Bookmaker what Hall Effect IC are you using?

I'm ordering a couple to sense Omni's motor current so when he bumps into something I can measure the current increase via an ADC port and make him back off.

Winstn60, These are not the exact ones I am using but close enough.

Hall Effect

Bookmaker thanks for that I've ordered the Sparkfun ACS712 breakout board so similar just hope they are sensitive enough. I need to measure how much current Omnibot takes trundling around now

Hello again, I didn't mean to mislead you but I am using the small ones with three leads that go high when in the proximity of the south pole of a magnet. How do you hook up the one you bought? What I mean is where do you hook up the terminals for the current being sensed?

#Bookmaker

No problem I understood. 2 pics attached basically the wire you want to sense in this case the power cable to the motor is wired through the sensor (big holes in pic)and the output will go to an EZ-B ADC port. 1 sensor for each motor.

I haven't got the sensors yet they may arrive tomorrow so this is all theory but can't see why it wont work. I'll report progress this weekend

Thanks, now I get it. That opens up alot of ideas. The posibilities are never ending. I just love it.