Electronic Focuser.. Progress so far..

[elusiver]

well... made some progress so far with the electronic focuser project i'm working on at the moment. I've tried to keep it as simple as possible, and used components that are easily obtainable here in aus. It'll be driven by a stepper motor, with a hand controller and also can be computer controlled.

Hand Controller:
Houses all the components.. bascially only 3 controls on it.. 2 buttons to move the stepper clockwise and anti clockwise, and a speed control.

Software:
Has continous run clockwise and anti-clockwise, that can be speed controlled. Also single step in either direction. Also coming is a preset function.. so you can have presets of positions of the focuser.

Motor Mount:
Don't know yet.. I ordered a crayford :D :) .. so I'm just waiting for it to come before i start seriously considering it. I want to make it a geared drive.. cause i'd prefer it to just a friction drive or a pulley as i think a gear would be more accurate.. which is what u'd want if u'r using the presets.

Now.. just want you guys for any input. Anything, suggestions, critisisms.. I'm no engineer.. and I'm not really one of those skilled people who is good at making and designing stuff like mick, asimov, mhodson etc... The truth is i had very very limited knowledge when i embarked on the project but i'm learning heaps as i go. It's just something to do on those cloudy nights :)

el :)

[asimov]

Look's really good EL! Still haven't got around to building mine as yet.
I'm sure it'll work real nice. :thumbsup:

[davidpretorius]

looks good so far

where did you get the stepper motors and controllers from and how much. I have an old guy that can make and fix anything. I will be eager to get my hands on some stepper motors and link to the computer.

there is a crayford on my dob that should be here soon, so i will check it out

[asimov]

one small point if i may....If you use gear's...how are you going to manual focus if you need to?

[elusiver]

from what i figure it should.. although there would be a tiny bit of resistance. but the motor does spin freely when it's not turning. So you should need it disengage anything as with some designs... which is what i wanted.

el :)

[asimov]

Interesting....It's against my policy to rotate an electric motor by hand, but upon thinking about that....It probably won't harm it as long as you turn off the power to it 1st?

:confuse3:

[elusiver]

rajah's probably the person to ask about this.. but i was under the impressions that that was one of the differences between dc and steppers..

el :)

[asimov]

Yeah, Laurie would be the one to ask for sure.

[RAJAH235]

It all depends on the final gearing. But, you'll have to have the power off, as already noted. Why not build a clutch/gear drive. Simply use 2 drive gears the same size, but with the clutch disk,(under spring tension), inbetween them? That way you can move the focuser manually. Won't you get similar focus adjustments/pre-set settings with a belt drive system?? The electronics look good. :thumbsup: :D L.

[elusiver]

Well i thought about the belt.. but i thought there maybe abit of play it in.. with the belt maybe slipping a little more the gears would.. therefore making the preset thing useless.. . As to a clutch disk... it sounds hard.. but.. i think i kinda get what u mean.. i'm kinda thinking something along the lines of the clutch system thats in my nitro rc car.. but probably abit beyond me.. at this stage ;) And of course the electronics look good.. it was a kit! from jaycar.. i'm not clever enough to design my own circuit :( i wish i was though. But i've just made some mods to the kit to suit the purpose and re-written the software to suit. I did this so that someone just like me, with very limited knowledge should be able to replicate it. Alot of the homemade focusers on the net require special skills, tools or equipment.. thats why i thought i'd try to make something thats close to being a kit that anyone can do it.

el :)

[RAJAH235]

Lex, This is sort of what I had in mind. It's an easy thing to make up. Just get 2 FLAT SIDED spur gears the same size, or file/machine flat. Pref. plastic, (D.Smiths, JAYCAR), & a bit of thin felt? as the friction material. Thread your shaft at one end for the nut...........etc etc. HTH. :D L.
ps. Not sure but, do the gears have a 'metal boss' with a grub screw for fixing to the shaft, or are they a 'press fit'? If a press fit, you might have to 'supa glue' them.

[RAJAH235]

Hey Lex, How's your electric focuser going? Any more progress? :D L.
2.

[elusiver]

not the past couple of days.. for a couple of reason.. didn't want to start thinking about the motor mounting until my crayford arrives, cause i don't want to base it on the r & p to find the crayford will require a different approach. I've goto finish off the hand controller and the app.. but i've had something taking up alot of my spare time.. the xbox. I just haven't been able to get off it the past couple of days. it's terrible.. the mrs has had about enough of it too :P ;) so i'm gonna try and take a break from the xbox this week(think detox.. betty ford)... so i'll probably get some more done then.

Another question though Laurie.. running power(signal to the motor) through something like an RJ-11 cable.. what can go wrong? obviously the wires very thin so i had my doubts but was gonna give it a shot anyway... but thought i'd might as well ask. Reason being is cause I'd like to use the twirly cable.. u know like off a phone handset..cause i reckon it'd look better.. and it'd be easier to make plugs cause i can just use an RJ-11 socket :)

el :)

[davidpretorius]

lucky you don't have a 5yr daughter that beats you at halo on the xbox, she cries tears if you even shoot a bullet near her vicinity, and whilst you are apologising, she shoots a rockey up my nose.

how much was stepper motor and where did you get it from . My town (**** smith and tandy) haven't heard of them!!!!

[RAJAH235]

Lex, The twirly cable might be a tad light, just try it tho! If it is, then make your own simply by cutting your required, heavier, cables to length & twisting them with a cordless drill. Just put the cables in the chuck & twist away till you're happy. The plugs/sockets that I normally use for power, are *2.5 mm DC power socket/plug*. These are designed for the job. They're neat as well.
David, try *oatley electronics* in Sydney or (www.jaycar.com.au) for the steppers & circuit.
HTH. Regards, L :D :D :D

[davidpretorius]

thanks, i shall have a peek

[elusiver]

dave.. here's the link. (http://www.jaycar.com.au/productView.asp?ID=KV3594&CATID=&keywords=stepping&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=) this kit is what i'm basing it on.. so it all should be simple to DIY :)

Laurie.. it's 4 wires.. which is why i thought to go for the RJ-11.. so i'll give it a go.. can't go for the 2.5mm socket.. cause i need the 4 signal wires. so i'll give the RJ-11 a try..

el :)

[RAJAH235]

Lex, have a look at these for more substantial units. :D L.
Hope you can read them.

[davidpretorius]

Thanks Lex, unfortunately "NOT compatible with Win 2000/XP"
And here is why

"Unlike Windows 95 & 98, Windows NT/2000/XP will cause an exception (Privileged Instruction) if an attempt is made to access a port that you are not privileged to talk too. Actually it's not Windows NT that does this, but any 386 or higher processor running in protected mode."

"There are two solutions to solving the problem of I/O access under Windows NT. The first solution is to write a device driver which runs in ring 0 (I/O privilege level 0) to access your I/O ports on your behalf. Data can be passed to and from your usermode program to the device driver via IOCTL calls. The driver can then execute your I/O instructions. The problem with this, is that it assumes you have the source code to make such a change. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
Another possible alternative is to modify the I/O permission bitmap to allow a particular task, access to certain I/O ports. This grants your usermode program running in ring 3 to do unrestricted I/O operations on selected ports, per the I/O permission bitmap. This method is not really recommended, but provides a means of allowing existing applications to run under windows NT/2000. Writing a device driver to support your hardware is the preferred method. The device driver should check for any contentions before accessing the port. <o:p></o:p>

Well, there are lots of routines, source codes, device drivers, dlls available on the internet who will make your task easy. Like userport1, porttalk, give-io, remove-give-io, inpout32, etc etc."<o:p></o:p>
<o:p></o:p>
<o:p>I will do some more investigation</o:p>

[elusiver]

the one i'm re-writing DOES WORK WITH 2k XP! using inpout cause starry night pro won't work with 98 :) :D i've got the output working fine :) all the hard parts done.. just the little finishing touches.

el :)

[elusiver]

thanks for the pic asimov.. will have a look through my jaycar and rs catalogues as well.. we'll wait n see if the rj-11 cable works first.

el :)

[davidpretorius]

hi lex,

are you running windows 98?, keen to see how you go with this!

[elusiver]

nop.. both my home systems and my lappy run xp pro.. my work lappy runs 2k.. :D so yes.. the motor does work with 2k and XP :) but it uses the parallel port.. i'm not even gonna think of trying to make something thats usb..

el :)

[davidpretorius]

definately very interested in how you got around this, without giving any secrets you may want to keep to your chest of course.

thru printer port with xp pro way to go. the toucam will be in the usb

[elusiver]

with a fair bit of searching :) i'm not gonna take credit for something that i didn't code myself.. trick was to use a worldwide google search ;) :P .. ended up finding some code in chinese.. and even though i couldn't make head to tails of alot of it.. ended up working in the end :)

el :)

[davidpretorius]

Hi,

As my toucam is currently plugged into the parallel port for the long exposure stuff and 1 usb port for general avi capture, that leaves the three usb ports the only option for telescope control. Did a search and found

http://www.usbmicro.com/

There is a stepper motor set up

http://usbmicro.com/odn/documents/197.html

I will have a look at whats involved and get back to you all

[elusiver]

dave.. looks good..

bit of a pain getting the phase sequence for motors though.. but i'm sure u should be able to get it for the one u'r using. Actually.. i think i might have a couple spare steppers in my junk box at home that u could use.. but u'd have to find out all the details.

So you'd probably got from the USB controller out to a darlington(uln 2003) array then to the motor coils. Definately doable.

el :)

[davidpretorius]

haven't got any motors or controllers yet, may take you up and buying some of your old ones. I spose my first step is to investigate controller first etc

[elusiver]

Update! The software is just about finished :D Just some final testing then figuring out how to make an installation package :D But this is pretty much the final layout. All controls are working and it's now saving the presets when you exit the program(got the text file thing sorted :D ). I think next week will be a killer at work as we're re-launching our website so realisticly I'd say work beginning on the mount maybe the following week, but have a couple of ideas on the drive(thanks rajah!) buzzing round my head.


el :)

[acropolite]

BTW David, There are plenty of stepper motors out there, for free, in old printers. I have a circuit diagram for an interface for Epson stepper motors (which are quite common).

[xrekcor]

I was thinking of building something similar using the DEC motor on my EQ5 mount. However since I dont need it to be puter controlled, I was intending to incorporate the clutch and gears that comes with it.

regards

[[1ponders]]

El if you get the chance to have a look at a JMI NGF-CM focuser. To switch from motorized to manual is simplicity itself. The motor is mounted internally but you should be able to work out something similar. There is s screw on the bottom of the housing that when you unscrew it slightly the the bottom of the housing drops down (its under spring pressure) and disengages the motor gear from the fosuser gear. When you want to use the motor again you just tighten up the screw to re-engage the two gears. You would loose your counter but there would be no pressure on the stepper motor at all, it being disengaged

[Wombat_In_Space]

El here are the photos of how I mounted the stepper and driving the focuser via belt drive, I haven't yet tested the computer control side of it yet I am hoping to get to test it this weekend.:)

[RAJAH235]

Looks good. Has it's own 'inbuilt clutch assy.'. Simple too. :D L.

[davidpretorius]

Well done Wombat, better than my piece of wood!!!

I have found that when running my direct coupled 1.8 degree stepper on the crayford at 1/2 step, i have ample amounts of steps to focus.

It feels like there are 10ish positions where the focus is spot on. I would need to test on a really still night, Bird was happy with the range I got without gearing

[Wombat_In_Space]

Well till I test it fully i have chossen to run a small size diference in the pullies I may go to running the same size pulley on both ends so it would end up 1:1:confuse3:

[Wombat_In_Space]

Well I finished the manual control box for the electronic focuser now need to find out why the computer control side of the unit is not working. :confuse3:

[davidpretorius]

is the computer on????

[Wombat_In_Space]

Yes the computer is on as I am typing on it:P

[davidpretorius]

is your keyboard there or are your fingers joined to your hands???

[Wombat_In_Space]

Well the focuser got first light tonight and worked great in manual mode still have worked out the computer glitch though it would have made it even better.:)