New Continuous Rotation Sensor with Position Feedback

erco

Senior Member
A totally unique and exciting new product, a CR (360) servo with an internal Hall effect sensor. Internal circuit outputs a PWM signal to give position feedback. I just got my hands on two, but have no time to play right now. Think will make a great Picaxe powered robot when I get a chance.

Discussion here.
 

newplumber

Senior Member
Hi erco that is cool ...and I know you will test it out and tell all the pluses and minuses (i hope)
Now I might have a chance to use a servo with out all the gears grinding sounds (over max degree angle) :)
 

erco

Senior Member
Oops, moderators please move this post to robotics. My bad!

First tests with a 20M2 are amazing! It's an absolute encoder (does not reset to zero at powerdown) and servo position is easily read with an ADC channel. Even an 08M2 robot could have 2 servos with feedback, a pushbutton and an IR receiver for input.
 

hippy

Technical Support
Staff member
Oops, moderators please move this post to robotics. My bad!
Actually it was moved from the finished project's robot section because, interesting as it is, it is not a finished project as such.
 

jims

Senior Member
erco...sounds interesting. Please post the servo ID (make & model) and the supplier; if possible. Thank you, JimS
 

erco

Senior Member
My quick experiment showing two simple ways (ADC vs PULSIN) to read the encoder PWM signal. I'm impressed that both methods output stable numbers right at the spec'ed duty cycle extremes of ~3 and 97% (slowly uploading video now, might take a few minutes).

 

erco

Senior Member
Picaxe 08M2+ saves the day. Note that the simple preliminary code attached does not handle the encoder max/min transition.


 

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newplumber

Senior Member
Now that is cool thanks erco
turn a wheel one way the other follows ...wonder if I could turn this into a "fingers snap" and "kids clean room" application
 

erco

Senior Member
VERY rough, but this video shows what I've been up to, recording and playing back a path on a modified Boebot. It's far from perfect, I just went for my usual minimalist approach with an 08M2 and the shortest code possible. The servo has some quirks, there's a big deadband at 1.5ms (making the speed response nonlinear), and it's very particular about control pulse timing, so the servos kinda chug along here. There are some fudge factors to tweak, the playback path is longer than the recorded path. Plenty of room for improvement!

I'll have to clean up and comment my spaghetti code before sharing, but it does work as shown.

 

newplumber

Senior Member
I didn't say it but are you sure those are "vitamin bottles" :) jk but thats neat thanks
I thought i was the only one with spaghetti code. yes when you can ,post it so i can cheat and skip reading arithimthormam stuff
 
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