Electronic Focuser.. almost there :)

[elusiver]

well.. been doing a little work on the focuser tonight. I've pretty much got the app done, well.. minus a fair bit of testing.. but i'm sure that will be done when it's out in the field.

The base of the project is this (http://www.jaycar.com.au/productView.asp?ID=KV3594&CATID=&keywords=stepping&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=) stepping motor kit from jaycar. The description on the Jaycar site says that this doesn't work with 2k & XP, and that's true with the software that is included with it. But my stepper app DOES work and has been tested with 2k and XP, but hasn't been tested with 98/Me :( Basically if you went out and got this kit.. did the assembly you'd see that this app drives the little motor just fine. The app has the ability to store presets, i'm not too sure how well this will work.. but I guess I won't know til it gets up and running. Say for vieweing jupiter in my 15mm the focus point is say 52 revolutions of the stepper. It allows me to store 52 and just hit a button to call that focus point up again.

I've also made a hand controller for when you want to use the motor independant of the PC.. but that's still in bits cause i got the wrong connectors last time I did a jaycar trip :(

I've begun work on the drive.. which I've pictured. Mine will be a gear driven system at first. But i'm sure as time progresses the drive itself will probably be changed and refined. Mounting the gear to the crayford was probably the bit that was worrying me the most.. as I didn't want to 'hard mod' it.. so that it could be restored back to original if need be. But it was as simple as unscrewing the nob.. boring out the gear and screwing it onto the base thing of the knob. No nasty glues or epoxies! :D

I'll post the first(and probably buggy as all hell ;)) version of the app.. and some pics on how i got the gear onto the crayford.

as always.. any input/critisicm is welcome and appreciated. :D :) :innocent:


el :)

[janoskiss]

Will it work with Linux? :P

[asimov]

Looking good EL :thumbsup:

[davidpretorius]

i am just about to buy this usb stepper motor controller http://www.ar.com.au/~softmark/page44.html

three motors can be driven.

what jaycar stepper did you buy, i am in our capital city (hobart) for next few days and would love to be able to buy a stepper motor.

also i see that 7.5 degree stepper motors with gearing seem to be the go for computerizing the dob for tracking

i have linked to the maths for converting ra / dec to alt/az, your set up for the focuser looks great and http://www.bbastrodesigns.com/ has been great for ideas for the two directions of movement for tracking.

i would love to be able to track and focus by end of october in time for snake valley!

[davidpretorius]

by the way, top work!!!

[elusiver]

:P :lol:

el :)

[davidpretorius]

linux!!! who cares????

[janoskiss]

OK. What 'bout Mac OS X then? :scared3:

[elusiver]

Dave.. from what it looks like that USB controller looks good.. but i think u'll need a 4-pole stepper for it to work.. whereas from memory the 12v stepper at jaycar(cat. YM2751) is a 6-pole. Also.. bear in mind that the phases and wire-outs can be different for steppers.. which means it may be some fiddling with either the wires or code to energise the poles in the right sequence to get the motor to turn. But.. definately doable as a project! :D As to the tracking project.. wildcard have usdigital encoders quite cheap :) was thinking about using their encoders in the DSC box project.. but have decided to push the DSC project back and take some steps into imaging.. by getting a webcam and modding the **** outta it. :D :D still deciding on the quickcam 3000 or a toucam.. as I'd like a toucam.. but since it's gonna be a 'project' cam.. maybe better to go with the cheaper 3000 so it doesn't hurt so bad when i break something :D

el :)

[davidpretorius]

no no no no no, programs only get written for buggy, virus ridden, crashing windows!!!!!!

when it is fool proof and running smoothly, then it goes to linux and the mac.

just ask bill gates about unix and who's company uses it!!!!

[elusiver]

for a 4 pole stepper.. prolly best to pick apart some old printers.. messy messy job.. but u get a fair bit of cool stuff outta printers.. but if you want a less messy, easier and more costly solution.. RS have them for $84(*cough*ripoff*cough*) :P but i'm sure if u had a search around there'd be a fair few electronics suppliers that'd have them.. probably alot cheaper than RS.

el :)

[elusiver]

since when did mac's have a parallel port :P :D ;)

el :)

[davidpretorius]

cool, why a 4 pole compared to a 6 pole? what is the difference. also as devils advocate, why do you need encoders with stepper motors? are they really needed?

i have toucam and a 3000, have given the 3000 to my old man. i am about to buy a t thread adapter and a eyepiece projection adapter http://www.telescopes-astronomy.com.au/toucam_philips.htm to use with my toucam. the 6mm fl of the toucam as prime focus is too much magnification with out tracking.

[janoskiss]

As a very part-time software developer, I have to disagree with that statement. UNIX is robust enough to handle buggy code/programs running on it. On the other hand, fatal bugs in a program-to-be often take Windows down with them. Hence for me (lazy programmer) Windows is a lousy development platform. Only once the major bugs are sorted out is a Windows port a viable proposition.

[davidpretorius]

true steve very true, Mike, how come my quote has been attributed to asimov???? i know i was using sarcasm, but not as much as asimov does!

[elusiver]

if your motorising the dob.. more than likely u'll be friction driving it.. and this even applies to gear/worm driving it to some extent, but there will always be a bit of play.. alot more if friction driving i would've though. You wouldn't run like the stepper to run 10 revolutions clockwise.. and expect it to be at the spot, because more than likely it wouldn't driving something that size. So you'd run turn motor clockwise unti encoder reaches the spot and you're there... spot on.. no play.. no leeway.. well as long as u'r encoder was fitted properly :P

el :)

[davidpretorius]

Hey El,


found some couplers

http://img-asia.electrocomponents.com/images/VC359723-09.jpg (http://www.rsaustralia.com/cgi-bin/bv/browse/Module.jsp?BV_SessionID=@@@@0402618 451.1124750658@@@@&BV_EngineID=ccciaddfhfddlmgcefeceef dffhdgmk.0&cacheID=auie&3302203572=3302203572&stockNo=3597361) Paradrive™ Oldham Coupling - Clamp Style (http://www.rsaustralia.com/cgi-bin/bv/browse/Module.jsp?BV_SessionID=@@@@0402618 451.1124750658@@@@&BV_EngineID=ccciaddfhfddlmgcefeceef dffhdgmk.0&cacheID=auie&3302203572=3302203572&stockNo=3597361)

at RS.

should be good for focuser attachment.

also geared steppers

http://www.electrosales.com/hurst/images/LSG42.jpg

http://www.electrosales.com/hurst/lsg35_geared.htm

this is all starting to look good mate.

[asimov]

I don't use sarcasm all that much. Sarcasm being the lowest form of WIT after-all? That's just your interpretation...I ain't responsible for the way you see it! :P

[elusiver]

i'm moving away from coupling now! :P things keep changing.. so i guess it's the way it flows.

using this
http://www.jaycar.com.au/products_uploaded/productLarge_8434.jpg


the motor will mount straight onto it and it will gear it down, but it works out to be a cheap ready made gearbox. then i can mesh it to the gear i've put on the focuser in the mounting. All looking good.. just gotto set aside the time to do it.

el :)

[mch62]

Elusiver did you look at the Jaycar AA-0352 stepper motor interface module.
Just wondering why you used the unit you have?
It may be the same thing just in case already to go?

http://www.jaycar.com.au/productView.asp?ID=AA0352&CATID=9&keywords=&SPECIAL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=306

Am interested in your results .
Mark

[davidpretorius]

i have this one arriving today or tomorrow. it is usb driven as the printer port is already taken up by imaging software for long exposures on the modified toucam

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

[elusiver]

yeah i looked at that... but from memory it couldn't be used indepently of a PC.. which is what I wanted so I could use it as a hand controller.


el :)

[mch62]

What's involved with using it as stand alone.

Thought about using small timing belts to the original focuser knob.
some of the robofocus mods use this method and as you say it's not a permanent change.

[elusiver]

the software i've written for it does work with XP.. it's based on some chinese source i found on the net for driving it under xp.. out of the packet the kit doesn't work with 2k/xp.

the circuit knows when its plugged into a computer. So you're hand controller is also your interface box.. so when you plug the interface box in to the computer it automatically switches to 'pc mode'.. then indepenant of PC you can use the interface box as the hand controller. To get it work to properly as a hand controller only took a couple of DPDT switches so it was sweet, and the manual speed control is in the kit.

el :)

[davidpretorius]

yes, xp has tightened up security so much the printer port is not as easy to get at.

that is why the usb port versions are starting to be more wide spread

[mch62]

just another link for steppers and controllers

http://www.oatleyelectronics.com/stepper.html

[davidpretorius]

great find, exactly what i have been looking for!!!

[elusiver]

hey guys... a couple of people have asked about this project.. it's progress.. and copies of the source.. well.. i'm selling the source for a bargain price of $100,000,000,000!!!! :D :D j/k

in all seriousness.. i think the last time i worked on it it was pretty much done.. had the mount made up and it worked quite well.. to a point.. and i'm sure it could be refined down to a very fine control.

At the moment though.. well.. i'm kinda homeless.. the mrs burnt down the kitchen.. noone was hurt.. but my pc is in storage.. and that's where the source is. Once we get back home i'll post the source up here.. so you can do whatever you want with it. :D

it's also why i haven't visited iis much.. i miss my dob.. real bad.. damn fire and burning....


el :)

[ballaratdragons]

Ellex!!!

Wondered where you went!!!

Gee, not good news mate, but nice to hear from you again. Welcome back! :thumbsup:

I hope you get everything sorted out soon.

[Aprid]

Have a look at www.interinar.com I picked up a stepper controller assembled and motor for approx $70AU delivered can operate in PC or standalone just req'd a couple of SPST switches and a potentiometer soldered to microstep, reverse and contol speed, works great in standalone I haven't tried running it with a PC yet.

[DavidH]

Hello Folks,

Thought I'd add my .02 worth to this thread by posting a snap or two of my homebrew stepper focuser. Stepper and gear are from a photocopier. The focuser is a JMI mini crayford. It has three holes in the focus knobs as standard. I simply drilled and threaded the nylon gear for the 3/32 bolts and use the bracket from the photocopier to support the motor. Took a little bit of playing with to get the gear centred on the focuser shaft, so that it would mesh properly with the motor gear.

Have also seen similar motor/gear combinations in the carriage movement of flatbed scanners.

The control of the stepper is via an Atmel microcontroller which has an infrared interface to a TV remote to use as a handpad. Sometime I intend to convert this to a radio handpad, and maybe write an Ascom driver for it. This will have to wait until I learn enough about writing drivers to actually :help: do it, however.:screwy: Does anyone here have any experience with this?

[Yogie-One]

Came acros this thread as I have also fitted a stepper motor to my scope, but, have a setup for my scope, which uses only a battery, a 12 position switch, 8 diodes, a 5 or 6 wire stepper motor, a mounting plate and a few gears.

The conection causes the stepper motor to follow the switch, forward or backwards, enabling it to be used as a driver for a focuser.

Total cost $3 (with stepper motor from old printer)

[iceman]

Great work Yogi! Perhaps you could write an article with bigger pictures and I can use it in the articles section!

[DavidH]

Well done Yogi, a simple but effective design that I am sure a lot of people could and will use.

[Karls48]

Here is a link to build simple and cheap unipolar stepper motor controller. I have build push button version and it work great.
http://www.beowulf.demon.co.uk/serial-stepper.html