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Author Topic: xbee's for stepper motor control  (Read 1942 times)
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I couldn't reply to topics from the old forum, and while I know this is an Arduino forum I want to accomplish this without an Arduino so I'm starting a new topic with high hopes.

I don't know anything about the Xbee's and their capability so here's what I'd like to do and hopefully someone can tell me if it's possible or not.
I want to use a rotary encoder (US Digital S1) to send a signal to an Xbee, transmit that signal to a receiving Xbee that outputs to a motor controller (US Digital MD2S) that's driving a stepper (Maybe this one).

I'm sure it's not this easy, so if this set up doesn't work maybe there's an alternative on the top of your head?
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I'm not sure if the Xbee actually has the capability... but check out the ATtiny85 or 13 @ sparkfun. It's like the ATMega328 in your arduino, but a lot smaller.


If that looks good, I can tell you some more info on using it.
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Ah bummer. I'm trying to find a wireless solution that doesn't require soldering, or at least very minimal amounts of soldering. What's the missing link? Data interpretation for the Xbee's? Would I have to connect Arduino's or something to make it work?
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ATtiny's are 8 pin DIP Packages... No soldering required. Just put it into a mini breadboard w/ the Xbees.


Good Luck!
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What capability is the xbee lacking? Interpretation of the a/b quadrature data from the encoder? Would I need two attinys to do the reading and converting? I've never designed my own microcontroller but I'll give it a shot if it's within my brains grasp. I had thought about just transmitting PWM but I can find a prebuilt stepper controller that reads PWM, and it seems like servos aren't going to be able to track over 360 degrees of movement.
Thanks for your help this far.
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**My clipboard in broken. I can post some of the links. You'll have to find them. Sorry smiley-sad **

The stepper you pointed out has 4 pins. ATtiny's have 8 pins, including power. So 6 pins left. 2 for stepper motor data (other 2 are power.), 2 for rotary encoder (plus 2 for power). That should work.

If you decide to use the ATtiny:


You probably don't need that $150 controller. Check out this:

arduino.cc/en/Tutorial/MotorKnob  (tutorial)

and you'll need an H-bridge from sparkfun. (COM-0315)

-OR-

Get the EasyDriver from sparkfun (ROB-10267)

If you look under the "Documents" section for a Portuguese tutorial... you'll have to translate it.


IMPORTANT: Stepper is rated for 12V you will need a 12V power supply for it, NOT ARDUINO POWER PINS!


Good Luck!
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How would I transmit the data with only one attiny? I'm even more confused now. I have read from a couple sources that the easydriver generates audible noise. The expensive controller is silent and microsteps to a far more detailed range. I could try servos and insulate them in a project box to try and limit the noise, but even with servos I wouldn't be able to get more than 360 degree rotation right? I need to spin an incremental or absolute rotary encoder and have some type of near-silent motor accurately track the encoder movement in both directions. Wirelessly. Im flexible on the exact ratio, but it should be something like 1 spin of the encoder is 1 revolution of the motor.  There are expensive solutions, I was just hoping there was some way to do it without spending $2500
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Or without spending $150. Please tell me what you want to do, completely. Don't include parts, just what your input is and what your output is.
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This is the end goal follow focus

The priorities of this project over a rag tag system I already have built are that it be wireless and near silent.
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OK. So you want to spin rotary encoder, which sends signal over RF to change camera's focus.

1. Does it have to be rotary encoder? What about a potentiometer?
2. Does it have to be an Xbee? You can get General Radio transmitters/receivers from sparkfun for about $5 each.


But, sticking to your original idea, I don't the xbees have the power to control steppers. But I'm not 100% sure...
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Pots won't give me full 360 degrees of accuracy unfortunately. Unless everything I've read about continuous rotation pots has been incomplete or inaccurate. I can find analog encoders that do the same thing as a pot, but the issue is still the type of signal. I don't think I'd have a problem making a pot wireless, or even an encoder that does PWM since I could probably hack a futaba remote and receiver or send PWM through the xbees directly. The issue comes down to what type of signal works with which motors. I need quiet and full continuous and repeatable rotation and it seems like a stepper is the best I can find, but then it becomes a matter of finding a stepper controller that accepts PWM. Ive seen some microchips that say they do just that, unfortunately building a stepper motor controller from scratch is outside my realm of intelligence. I like a challenge but I know my limits.
I really appreciate your help though.
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What if you got a full rotation servo?


-AND-


Say your pot has 180 degrees rotation. Adding a 1:2 gear set onto the pot will give it 360 degrees:

Pot has a 50 tooth gear on it. You spin 25 tooth gear. Twice the range. Ta da. As long as your ADC has high enough resolution, you can add larger and larger gears!
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