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Topic: Just starting -feeling confident. a couple of questions (Read 1 time) previous topic - next topic

PeterH


On the subject of timeslicing this article explains it reasonably well


We're not asking you to explain the buzzwords you used in your post. The point is that they are irrelevant to the problem. We need to understand what your solution is trying to achieve, not the software mechanisms that you think will be needed to implement it.
I only provide help via the forum - please do not contact me for private consultancy.

Botolph


Personally, given the requirements, I would think that a reasonably gutsy stepper motor would be the easiest solution.  600 rpm isn't CRAZY fast, but it's not unreasonable either.  Sixty degrees is just 1/6 rotation... So that isn't a huge deal.  Reasonably high torque is easily done with a stepper, and they can be very fast....


Many thanks.
Can you suggest a manufacturer or model?

focalist

#12
Dec 27, 2012, 04:29 pm Last Edit: Dec 27, 2012, 04:55 pm by focalist Reason: 1
http://www.automationdirect.com/adc/Shopping/Catalog/Motion_Control/Stepper_Systems/Stepper_Motors_-z-_Cables/STP-MTR-17048?utm_source=google&utm_medium=product-search&gclid=CP-86szxurQCFQJx4AodYzMAoQ

Now, that's just the first Google hit- but if you pull up their spec pdfs from near the bottom of the page, 600 rpm isn't a problem, in fact the specs are given for the range of 100-2250 RPM as a standard it looks like.

Those are pretty much industry standard stepper motors, and any maker will have something similar.  Since most of the libs for arduino have been written for unipolar stepper motors, and the wiring for them is easier (no h-bridge needed), I would choose a unipolar motor.

I am not recommending any maker or seller, by any means-  so shop around.  The device you need however- very easily gotten, and isn't particularly expensive or hard to find.  I probably have half a dozen in a box that would fit the bill, I rip them out of printers (a very common use for small stepper motors) before they are sent to the great recycling bin in the sky.  For driver circuitry, you'll need a reasonably hefty couple of switching transistors as the windings are going to want a bit of current.  There's also dedicated chips for this purpose.  If you want to avoid the wiring bits as much as possible, look into a motor shield (http://arduino.cc/en/Main/ArduinoMotorShieldR3) or (http://www.ladyada.net/make/mshield/) or others.

Stepper motors work by taking "steps", in the case of most of the ones linked above, they have a step of 1.8 degrees.. 200 steps per revolution.  This is going to get you pretty darn close to exactly 60 degrees, but not exact.  I'm betting that will be within spec for your use, if not, then it's a matter of gear-reducing the output for accuracy and increasing the speed to compensate.  Note, that is using FULL stepping, if using half-stepping or microstepping you are more accurate but provides less torque.
When the testing is complete there will be... cake.

Botolph

Hi,
eventually, cold and flu intervened to distract me, I have purchased a hybrid stepper motor. As I need to move in approximately 60deg segments and at most a single 240deg turn Bipolar Parallel seems the best option.
I also have the Arduino Motor Shield.

Any advice on driving this greatfully received.

Motor Spec:
4.5V 
2.5V per phase
2 ohm/phase
3.6mHz per phase

Motor: http://www.arceurotrade.co.uk/projects/stepper/180Ncm%20Stepper%20Motor%20160-010-00200.pdf
Choices for driving a hybrid motor http://probotix.com/stepper_motors/unipolar_bipolar/

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