Stepper motors from dead printers

[avandonk]

Had a morning of extracting stepper motors from some dead printers
I have been collecting.Also some servo motors.Here's a couple of pics.

Bert

[asimov]

Yes, they do come in handy eventually dont they...I have a box full of them that came out of old electric typewriters (my EQ mount is driven by one) & various other motors from all sorts of equipment.

[davidpretorius]

some good stuff there, the 1.8 degree 5 or 6 wire bipolar are the best i reckon. I have one that is driving my focus with no gear reduction and i have more than enough step range to focus with.

[rmcpb]

How do you go about controlling one of those motors??

[davidpretorius]

a stepper motor controller from dse or rscomponents. i have bought a $85 usb version as that is friendly for my computer. I can control up to three motors off this board by sending signals to the board from my computer.

http://www.ar.com.au/~softmark/page44.html

[ving]

fair enough... you could drive a dob with those couldnt you?
if only I had the knowhow (and time) :)

[rmcpb]

Is there a simple way to control these motors without the need to have a laptop on hand?

[avandonk]

Dave how is the speed detemined with that USB controller is it set in software or is it as shown, slow med fast?
I have got a parallel port driven controller and was thinking of getting the USB version you refered to.

Bert

[davidpretorius]

yup,


you have to gear down the ratio as these things will step one whole step at 1.8 degrees and half step at .9 degree. this is too much as the earth is rotatinig slower than that. You basically need it to step at least 15 times a second so that you can do deep space photography.

roughly 24000:1

I am buying gary beals to have a play with and then working with mick pinner to get a locally made version up and running for next year.

You want to be able to make it real easy for people to fit to their dobs for tracking and goto etc

[avandonk]

There is use a crystal timer or LM555 timer chip plus stepper chip.Lots of stuff on internet.

Jaycar have a book for about $15 dollars on steppers and their control,getting it today.

Bert

[davidpretorius]

software, so you determine what slow medium and fast is.

there would be a limit in terms of recovery time from the preceeding pulse saying "step" to the motor, but you can get your software to pulse once a second, 1000 times a second. it is up to how you write the software.

with the usb one, you get that little program as shown. if you can program in visual basic , visual c# etc, then you can add a little active x component to your code to interface quite easily to it.

If you have no idea what i just said, i would be more than happy to write some code for you cos of all your kind and generous gestures!

what do you have in mind for the stepper motors?

[avandonk]

Here's the worm thats going to drive the worm on ballaratdragons mount.

150:1 and 240:1 ratio is 150x240= 36,000:1 should be smooth enough.

Bert

[avandonk]

Thanks Dave I will order a couple.The problem with the parallel port controller is that I have to switch between it and the parallel port relay box for autoguiding.

Bert

[davidpretorius]

these pictures are what i have bought from gary.


it is not laptop linked, i intend to make it that way, but this is wht mel bartels has been working on for a long time

http://www.bbastrodesigns.com/

[davidpretorius]

yes exactly!!! - parrallel ports and com ports are all full with other stuff, whereas you can expand your usb ports

do you need 2??

each card has three motor controllers

[avandonk]

Yes dave need two, one for me and one for kens mount so he can use the long exposure mod of the ToUcam on the parallel port.

Bert

[davidpretorius]

that looks like a 4 wire unipolar stepper, so you need to use 1 1/2 of the three controller ports. I was just talking to the manufacturer not two days ago re this. I will ask him exactly how you program the software to pulse it.

i am just digging up my notes and calcs on this................

[avandonk]

I have got more steppers see pic at start of thread.The biggest motor in the middle is six wire the others are five.I was thinking of using the six wire for Kens RA drive.I'll have to check the step size it looks like a double layer it is 7.5 deg. ie 48 steps per rev. just counted them.Shoud be able to half step it.
What I want it for is to build a stepper focusser for the new manual 300mm F2.8
Fluorite by just running a toothed belt around the focussing ring on the lens.

Bert

[davidpretorius]

.25 arcsec to 1 arcsec is the suggested step sizes for smooth transition during imaging.

therefore 3.75 degree half step needs a 54000:1 for .25 arcsec, and 13500:1 for 1 arcsec movement.



for focusser where i have directly coupled it, at .9 degrees in 1/2 step mode, i get about 7-10 odd steps where the focus hardly changes due to seeing etc.

so you would only need to gear down at 4:1 or 5:1 to get that .9 step and your focusser will be nice and fine, but not too fine!!!

[avandonk]

So 36,000:1 meets with your aproval Dave? ...Dave?

Bert

[davidpretorius]

i am very new to this as i am yet to build one myself, but 36000:1 should be very good. at the end of the day, a 1.8 / .9 stepper could always be swapped, if the extra resolution was required

[ving]

why wait till the end of the day davo? :confused:

;)

[avandonk]

Yes thats what I thought.Thanks, if the 48 step motor is to coarse and induces unwanted movement we can always get a 1.8 deg.


Bert

[avandonk]

davidpretorius have you seen these,the top one, runs off the serial port
http://www.oceancontrols.com.au/motor_controller/stepper_motor_controllers.htm

How difficult or otherwise would they be to program.Any advice please?
I saw these some time ago I got the parallel port relay box from them.
Bert

[davidpretorius]

i personally have not played with serial ports. it mentions ascii commands. I could contact them to see how well they can be programmed in Windows if you would like?

[avandonk]

That would be great Dave thanks.

Bert

[avandonk]

That would be great,thanks Dave


Bert

[Merlin66]

Yes is the answer. I don't remember the IC chip #, but with a very simiple R-C 555 timer circuit you can get the steppers to drive at different rates.
I use this set up to drive a 1/2" threaded rod and a moulded arc on my 6" f3.5 Poncet mounting.

[Merlin66]

For focussing, it depends on the thread pitch of the focusser. Usually within 0.001" is certainly "precise" focussing. The speed of the motor/ step size should be based on this calculation. The .25 to 1 sec arc limit is usually for fine tracking ( in RA) and achieved by mini stepping the motor ie 1/10 of a step as per Bartel's drivers. I'm putting together a 1.8 deg/step stepper with a 60:1 gearbox and a final 20:1 roller drive ie 1300:1 to give fast GOTO movement at 4 deg/ sec and tracking at 0.5 sec arc.

[davidpretorius]

my dob driver arrives next week from gary in NZ (thanks gary) and i will be very interested in the mechanical setup.

That is a great range of speed. Obviously using 1/10 microsteps?? Did you source your gear locally?

[Merlin66]

Can't honestly remember where the motors originated, collected over the years. The 60:1 gearboxes from CBC model NRV030, the 20:1 comes from a 35mm wheel driving on a 760mm diam disk. The driver software is the Mel Bartels three motor design ( includes third stepper for field rotation)

[shredder]

Hi guys,

Writing to the serial port isn't much of a problem. I have had to do it many times on different occasions, though I should also say I write software for a living so it depends on your programming background (I have code for Java or C++ for doing this).

I also have an electronics background and would agree with Merlin66 that a 555 timer chip is a cheap and simple solution to driving a stepper motor and there are lots of examples of how to do it. Even the spec sheet has a design for doing it (from memory) and the components needed cost bugger all (and is very low on power usage).

Anyway if anyone really is keen to program the serial port let me know and I will dig up some old code for it.

Cheers

Michael

[davidpretorius]

cool, windows xp sp2 has caused some hassles talking to the serial and parallel ports by the sounds of it, so i am using the usb port with visual studio 2003 .net.

visual c sounds a lot better to talk to the hardware ie cameras and ports etc!

[rmcpb]

Question for the whizkids --- I have been happily pulling apart a printer BUT the electronics in it are all 24V not 12 as I expected. Is there any way to use these motors in a 12V system?

Maybe a dumb question but I know diddly squat about electronics.

[RAJAH235]

No, Rob. :D L.

[rmcpb]

Not quite the answer I wanted :(

[Starkler]

Possibly, with an H-bridge type switching circuit.

[rmcpb]

Too hard, I'm flat out understanding serial and parallel circuits!!

[ballaratdragons]

What about those things that work the opposite to a normal transformer. They put the voltage up instead of down? 12v in and 24v out.

[avandonk]

Steppers do not really have a voltage rating just an upper voltage not to exceed.They can run from a wide range of voltages.The stepper controller generally controls or limits the current so the stepper motor does not overheat.Some steppers can actually draw more current when they are stopped as the coils are energized so there is a holding torque.

12V should be more than adequate for most steppers.Some controllers actually pulse the applied voltage at a higher frequency than the step pulses so a higher voltage can be used and so providing more torque.

Bert

[RAJAH235]

Do you mean a voltage doubler, Ken? T'is a simple circuit but, why not just use '12 volt' steppers? They're very cheap.
Rob,Stepper driver kits are also avail & cheap from u know who. Try Oatley Electronics/D.Smith etc etc. :D L.

[FNQ_View]

As avandonk said, steppers don't really have an operational voltage. It depends on how you control them. My big box of steppers are all 1.8 deg/step and the listed voltages range from 3.6 to 9.4. All motors came from copiers that have supply rails of 5 & 24VDC.

The one on my desk is listed at 4.2V & 1.5amps, weighs in at 600g. These are fairly typical motors to salvage from copiers.

Mick - Xerox Technician

[shredder]

For those still interested in controlling the Serial Port of the PC here is a link to a good Java Tutorial for it.

http://www.javaworld.com/javaworld/jw-05-1998/jw-05-javadev.html

Note there is a lot of assumed knowledge in these tutorials, but it does show the basics of how to do it.

Cheers

Michael

[RAJAH235]

Ta Mick/Michael. Wasn't too sure re; applied voltages. All the circuits I've come across have been run on 5/12 volts only for the 'ease of access/simplicity/cost' factors, ie; batteries/plug packs. Should have looked more closely @ the circuit I posted. It shows/states you can apply up to 35 volts to the steppers.......:shrug: :D L.

[Merlin66]

Just bought a kit from jarcar for $45 does both 555 manual and parallel port control.

[avandonk]

What kit was that? Thanks in advance

Bert

[Merlin66]

Comes with a small bi-polar stepper motor and a couple of versions of software ( two for windows and one for DOS)