Digital, Temperature Compensated Focusser.

Dave,

Are you getting PCBs printed or are you using a prototyping/breadboard for the circuitry?

Darragh

Just intereseted as ive noticed, if you hit a hurdle, rather than look to purchase a solution like most of us do, you invent something!!!

Fintan, No I don;t mind those questions at all. I'm an IT professional (working for CIÉ) for a living. Electrical engineering is just a hobbyhorse of mine. Since I was a kid I've always been into making stuff. (and breaking stuff too).

Making astronomy stuff is a great interface between two hobbies. There is great satisfaction when you get something to work. So far my DSLR controller and dew zapper have been total successes. (<note to self> Get the finger out and get that dew controller written up and published). The dew controller would have cost me several hundred. However the one I built does the same job and cost only about 40euro in parts.

Fintan you'd actually be amazed at how simple some of this stuff is. PIC microcontrollers are little tiny computers that do most of the work in these devices. The circuitry in using them is actually relatively simple to understand once you've studied it a bit.

Are you getting PCBs printed or are you using a

Initially I'll be printing and etching the PCB myself for prototyping. Once I'm sure it all works and if others are interested, i'll get a batch made professionally. If only one or two want them I'll just make em myself.

It's not going to be possible to use breadboard because of the non-standard pin configuration of one of the major IC's used.

Sounds interesting Dave. Some valid points made about the temperature notification being a little like overkill perhaps, but if you can add it during the construction, then why the heck not. Don't foret to take some pics along the way.

Seanie.

Dave,

Any news on this project?

Darragh

Update 18 Feb:

Well after a long period of head banging I decided to go back to the drawing board on this one.

As it turns out the SLA7062 turns out to be a real nightmare to use. I was never able to get the current loading right and as such vibrations and torque (or lack of it) were an issue. Also the design would be tied to pretty much a narrow range of stepper motors with this IC.

Never to admit defeat, I re-designed the circuit based on a simpler method of driving the stepper motor using an L297 motor driver coupled with a quad darlington transistor array. The result works an awful lot better than the first iteration.

I also decided I needed to produce better PCB's. The method I was using was less than ideal. PCB's require exposing using UV light. UV exposure units are expensive. So after a bit of research, I decided to build my own using UV leds. In case anyone else fancies doing this, I wrote up a quick article on how to build one of these exposure units here;

webtreatz.com/content/view/60/73/

The next step is to test it on the scope and then write the ASCOM driver. I'll update again when I have tested it a bit further.