Building a GOTO Mount

[Neil WyattModerator @neilwyatt]

Well, more or less of the final straight now. Tomorrow I will take a few pics of the control box and gear'boxes'.

Some little tweaks needed to make the 'user interface' friendlier.

Neil

[Cornish JackParticipant @cornishjack]

Neil – apologies in advance

Having just had ALL the (overloaded) shelves in my new workshop/garage collapse (DON'T use normal rawlplugs in Celcon blockwork!!!), I'm bored and grumpy so read this thread … understood very little but absolutely fascinated by one of your earlier contributions – "a nice small project box with five coloured push bottoms – I found out why they were cheap on eBay – the bodies have a tendency to melt during soldering!" … the mind truly boggles!!

and thank you for the broadcast scam warning.

rgds

Bill

[Douglas JohnstonParticipant @douglasjohnston98463]

Neil- just seen your picture of the pcb you made and I am truly impressed with the quality. Did you use a printed mask and UV exposure on coated board or some other technique?

I have been making printed masks for years but have found the quality of print very variable. Getting a good dense solid black image can be a real pain and I have had to resort to overlapping more than one layer to achieve this.

If you have a good technique please spill the beans.

Doug

[Neil WyattModerator @neilwyatt]

Posted by Cornish Jack on 24/06/2016 23:51:10:

absolutely fascinated by one of your earlier contributions – "a nice small project box with five coloured push bottoms – I found out why they were cheap on eBay – the bodies have a tendency to melt during soldering!" … the mind truly boggles!!

If you leave the soldering iron on the tabs too long, they melt. While I suspect the plastic was chosen because something with a bit of 'give' was needed for the waterproof design, I suspect that in practice it makes them a bit too fiddly for mass production, and that's why they have ended up being sold off cheap. Soldered with care they seem to work perfectly well and you can get five nice colours.

Neil

[Anonymous]

Posted by Neil Wyatt on 25/06/2016 09:24:12:

If you leave the soldering iron on the tabs too long, they melt. While I suspect the plastic was chosen because something with a bit of 'give' was needed for the waterproof design………..

I suspect you over-estimate the 'design' process. The plastic would have been used because it was cheap, and cheap to mold, with little or no consideration of fitness for use.

It is not a new problem. It must be 40+ years since I discovered that cheap toggle switches melted when you tried to solder to the tags. Quality switches, which use thermosetting plastics for the body, don't have the same problem. Cheap connectors can also have the same issues.

Andrew

[AjohnwParticipant @ajohnw51620]

They probably melt as they have been designed for use by people who solder all day using a very hot iron.

Very hot in my view that is. I spent some time working in a place that had no facilities to remove flux so they used a special solder and flux along with by normal standards a rather cool iron. Later when I was sold yet again I worked with the "hot iron" crowd and soon realised that the tip I normally used made life more difficult for me. They could solder way way more quickly than me as well.

Mount gearboxes ? More expensive mounts have always generally used rather large worm wheels. Way way bigger than Skywatcher for instance. There are many attempts to get round that including very very high resolution direct encoding but personally if making one myself I would stick to a big worm wheel – ideally no other gearing of any sort at all.

John

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Edited By Ajohnw on 25/06/2016 09:50:25

Edited By Ajohnw on 25/06/2016 09:51:01

Edited By Ajohnw on 25/06/2016 09:51:31

[Neil WyattModerator @neilwyatt]

Posted by Douglas Johnston on 25/06/2016 09:18:21:

Neil- just seen your picture of the pcb you made and I am truly impressed with the quality. Did you use a printed mask and UV exposure on coated board or some other technique?

I have been making printed masks for years but have found the quality of print very variable. Getting a good dense solid black image can be a real pain and I have had to resort to overlapping more than one layer to achieve this.

If you have a good technique please spill the beans.

Doug

I have a home-made light box (in an ancient wooden burglar alarm battery box) and use pre-coated boards (usually). I use a 1200 dpi laser to print the masters on laser film and design them in Eagle. I develop with dilute caustic soda (half the strength recommended by most online sources) and etch in ferric chloride because I like the smell*

Neil

*perhaps as a vegetarian this is the only time I get the smell of 'blood' (= smell of iron) in my nostrils and it appeals to my inner carnivore!

[Cornish JackParticipant @cornishjack]

Still waiting for the proper wall plugs, so will try again …

"a nice small project box with five coloured PUSH BOTTOMS – I found out why they were cheap on eBay – the bodies have a tendency to melt during soldering!"

OK, so a bit childish but at 80, I'm allowed to be!! … so there

rgds

Bill

[Neil WyattModerator @neilwyatt]

Posted by Ajohnw on 25/06/2016 09:50:06:

Very hot in my view that is..

Mount gearboxes ? More expensive mounts have always generally used rather large worm wheels. Way way bigger than Skywatcher for instance.

How hot is way hot? I use 350-360, I wnt up to 380 for a bit when I go a temperature controlled iron and its great for solder tags etc. but I found it too aggressive for PCB work. Best thing about the TCS Antex iron is that although nominally it's the same temperature and bits as my old CS 15W iron, it at 50W it can pump extra heat in quickly.

Gearbox – just to turn the worms, I'm having to live with my Skywatcher EQ3 for now, although I have been musing about ways of making a more robust mount next year. I want to see what difference guiding makes first, plus as I don't do narrowband I can't imagine myself wanting to do subs longer than about five minutes even in dark skies.

A mini-lathe headstock and spindle fitted with taper rollers would make an excellent starting point for a mount. Easy to fit a DEC ararngement to the flange and a nice solid casting for the body.

[AjohnwParticipant @ajohnw51620]

In Weller terms 8 or maybe even 9 Neil. I always used 6's. 6's are 310C, 8's 425C, 9's 480C. I'd say 8's were used most often but there is a need to be very quick. I had to check these temperatures on the web and notice that RS mention that 7 or 8 is most appropriate for lead free.

Going on a variable temperature iron I bought at work when my weller went phut these higher temperatures do need the attention to detail Weller put into their tips. 7's are 370C. I think the numbers need two zero's sticking on the end to find degrees F. They are one of the few things that have been around for donkeys years and never changed.

Me – well I always wished I had bought another Weller at work as the tip needed very frequent cleaning and just didn't wet as well.

John

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Edited By Ajohnw on 25/06/2016 13:29:42

[Douglas JohnstonParticipant @douglasjohnston98463]

Posted by Neil Wyatt on 25/06/2016 11:15:44:

I have a home-made light box (in an ancient wooden burglar alarm battery box) and use pre-coated boards (usually). I use a 1200 dpi laser to print the masters on laser film and design them in Eagle. I develop with dilute caustic soda (half the strength recommended by most online sources) and etch in ferric chloride because I like the smell*

Neil

Thanks for your description Neil, that is exactly how I make my pcb's but I have considerable trouble getting good contrast masks with my cheap Samsung black and white laser printer. What make of printer do you use? I have tried proper laser film but found good quality tracing paper just as good and a lot cheaper. It looks as if I may have to upgrade my laser printer ( I notice a replacement toner cartridge costs more than my whole printer cost )

Doug

[Neil WyattModerator @neilwyatt]

Posted by Douglas Johnston on 25/06/2016 13:29:24:

Thanks for your description Neil, that is exactly how I make my pcb's but I have considerable trouble getting good contrast masks with my cheap Samsung black and white laser printer. What make of printer do you use? I have tried proper laser film but found good quality tracing paper just as good and a lot cheaper. It looks as if I may have to upgrade my laser printer ( I notice a replacement toner cartridge costs more than my whole printer cost )

Doug

Snap… the Samsung here is 600DPI and when you have a very small tracks or SMT pads they don't come out anywhere near as even as with the 1200 dpi HP.

I used to use an inkjet with special film, which worked fine.

Neil

[Neil WyattModerator @neilwyatt]

Posted by Cornish Jack on 25/06/2016 11:19:30:

Still waiting for the proper wall plugs, so will try again …

"a nice small project box with five coloured PUSH BOTTOMS – I found out why they were cheap on eBay – the bodies have a tendency to melt during soldering!"

OK, so a bit childish but at 80, I'm allowed to be!! … so there

rgds

Bill

I think the correct reply is 'LOL!'

Neil

[Neil WyattModerator @neilwyatt]

Some pics of the controller box.

Now to focus on feature bloat seeing as a clear night to try it out is unlikely before 2017…

Neil

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