DIY PC control for Skywatcher Autofocuser

[Glider]

Here is my DIY replacement for the standard manual hand controller that comes with the Skywatcher Auto Focuser.

This connects to a USB port on my computer and is controlled by a small Visual Basic program that I have writen. Connection to the motor is via the usual connector on the end.

The program lets me focus in/out in steps that are selectable from only noticable with a magnifying glass to continuous traverse.

[TopHouse]

Looks like you're powering from a PP3 then as the original handset? probably better than powering from the USB anyway as it will only flatten the battery quicker.

Have you had chance to give it a good tryout yet?

What's the serial connector for?

Edited August 16, 2010 by TopHouse

[Glider]

Yes, as a first pass I kept the battery for powering the motor. I use the USB just to control and power the switching circuits.

When I have a better idea of what current is being drawn by what parts I can make a small change and try powering the motor from the USB aswell, it looks like it will be OK.

Have tried it indoors but not in anger yet.

The VB program simply sets RTS high for motor in and RTS low for motor out and throws a DPDT relay.

The motor voltage is fixed at 6Vdc using a regulator off the 9V PP3 which is where I normally set the old handset potentiometer anyway.

Sending a variable length sequence of zero's on the USB TX turns the regulator on and off.

It's not a serial connection, it's for connecting to the motor, it's just a convenient socket I had lying around!

Edited August 16, 2010 by Glider

[tooth_dr]

Is this going to be available as a completed product or plans? This is similar to the FCUSB device?

[Glider]

I hadn't thought about it, would enough people be interested?

I'd lay out a proper PCB, then I guess I'd do it as a kit or ready assembled. I'd have to cost it up.

[Black Knight]

You guys are a seriously clever bunch I wouldn't have a clue where to start with something like this!

[Glider]

Funnily enough, I start with the case or box that I want to put it in and then work backwards!

That way I never end up with something that's always going to look untidy and only part finished.

[Black Knight]

Seems as good a place to start as any I guess

[tooth_dr]

I'd be interested for sure cost depending. One more thing to control without touching the scope.

[Parallax]

Just a quick suggestion.

For those that use USB to serial adaptors, 4 COM ports might not be enough to choose from. You can alter your code quite easily to use a drop down box as I have done in the attached pic. The code is somewhere in the VB help. It populates the combo box with all the installed com ports.

Nice and easy solution by the way.

Steve

[Glider]

That's good, I'll do something like that, have you got a pointer to where in the VB Help it appears, or even a txt copy of the relevant code. For my own prototype I knew I could force the box to always be on one of the first four comports so didn't bother.

Just so it is clear, this box connects directly to the USB on the PC using a standard USB lead. There is no need for a USB to serial converter, it is built into the box. The 'serial' type connector is just a convenient connector I had lying around and is only used to connect to the motor.

Edited August 17, 2010 by Glider

[Psychobilly]

Nice Project

Peter...

[George]

A parts list and schematic would be handy looks an interesting project, I doubt whether the USB would power the motor as the USB power is only 5v....worth a try tho if it would do away with the battery.

[TopHouse]

A parts list and schematic would be handy looks an interesting project, I doubt whether the USB would power the motor as the USB power is only 5v....worth a try tho if it would do away with the battery.

Someone who built a similar unit on here says it does, and I think the commercial FCUSB unit does as well.

[Parallax]

In the VB Help type "serial ports availabilty" into the 'Look for' box.

Here is the code. They have used a ListBox but you can use a ComboBox.

Sub GetSerialPortNames()

' Show all available COM ports.

For Each sp As String In My.Computer.Ports.SerialPortNames

ListBox1.Items.Add(sp)

Next

End Sub

As for using the USB supply for the motor - I have, and it does work BUT if you are pointing near the zenith with a lot of weight hanging off the focuser then it might struggle.

Steve

[Glider]

Cheers Steve, that's what I thought might happen so I kept the battery option but since other units don't struggle when run off the USB it should be possible.

The pot on the manual hand controller seems to be set up to supply between 2 and 7Vdc to the motor so 5Vdc is well in range, I'm thinking of current more than anything.

The LM317L regulator is rated at 100mA which is suspiciously close to the basic limit of a low power USB device!

Anyway, so far so good, it all works well.

I'm looking at how much a proper job with a proper PCB would cost.

[Parallax]

You will find that the SW motor draws very little current (IIRC <20mA with no load). This increases when you put a load onto it, but I can't remember what it increases to!

Steve

[zedock]

would you mind sharing VB source with us, please? i'm not interested in any derivative work, i'm just a programmer who likes to study other people's interesting code (and this seems interesting) :-)

[Glider]

I'll have to put a meter across it with and without a load to see what it actually is.

As it is it is happily traversing my 1000D in and out and my focuser is 'tight' as I've made the 'PTFE oven door tape mod' to it to reduce slop and sag.

The code to find available comports works great.

Edited August 17, 2010 by Glider

[Steve 1962]

Looks good - I'd be very interested in plans, part lists etc. or a kit or a finished product

[gary1968]

A nice little project that Glider, I would be interested in plans or finished product if you get rouind to it m8.

Gary

[Glider]

Out of interest I've had a crack at a PCB.

I've also costed everything up assuming I'm getting 10 off kits of parts at a time from Farnell.

A complete kit looks to be £56.

[yesyes]

Just for my own understanding, is auto focuser the same as motor focuser?

I always assumed that an auto focuser would focus automatically, as in analysing the image and adjust focus like a digital camera does. And a motor focuser has buttons or computer control but human eyes decide whether the image is in focus or not.

Or did I get this wrong then? ;-)

[Glider]

I think you are right literally, but people just seem to refer to the SW 'thing' as an 'Auto' rather than what it actually is which is a 'Motor' focuser.

However, link it to some hardware and software, as I'm trying to do and you could use it as part of an automatic focusing system.

[Starblazer]

Definately interested in something like this