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.
Houses all the components.. bascially only 3 controls on it.. 2 buttons to move the stepper clockwise and anti clockwise, and a speed control.
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.
Don't know yet.. I ordered a crayford .. 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
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
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.
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. L.
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.
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. 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.
Last edited by RAJAH235; 25-07-2005 at 03:52 AM.
Reason: extra info.
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 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
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
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-comfficeffice" /><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>I will do some more investigation</o:p>