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Old 1st May 2017, 10:34 am   #1
MrBungle
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Default More homebrew computerless PCB progress

I got around to doing another PCB, this time for a new oscillator for my Heathkit IB-1100 which was heavily mutilated by the previous owner. Had a good think about the previous attempt this time and came up with some improvements. I have two DIP packages on this board so brushing the nail varnish on was a no go. Process is now as follows:

1. Draw it on squared paper at 5mm per 0.1 inch. Use black bic to draw holes, red bic for tracks and blue bic for part outlines.
2. Cut a piece of FR2. Stanley knife both sides until about 80% of the way through then snap.
3. Tape some veroboard to the bottom of the board as a marking template.
4. Mark all the holes from the design onto the bottom of the copper with a mechanical pencil.
5. Drill them all with a Dremel. If I'm honest I didn't bother using the stand.
6. Scrub the board with fairy and a kitchen sponge.
7. Draw the tracks on with fine single lines only with a lumocolor marker. Don't fill or do anything fancy.
8. Cover copper side with decent quality masking tape. I used Tamiya stuff from Hobbycraft.
9. Use a scalpel (x-acto) to cut the islands out of the tape. Do this under good lighting.
10. Paint the whole thing heavily with black Primark nail varnish and let dry.
11. Peel off the negative areas of the masking tape i.e. the bits that you want etched.
12. Float a tesco value Tupperware box in a sink of boiling water and put some ferric chloride in it.
13. Chuck the board in and whizz around with a cocktail stick until etched. Takes about 5 minutes.
14. Dispose of ferric chloride (back into bottle) and rinse board.
15. Scrub off all the nail varnish with IPA and a tissue.
16. Run all the holes through with a Dremel again to get the gunk out and scrub the board with a scourer and fairy again.

Result:

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Pretty good definition and good resolution. Total process after the design took about an hour which is fine for a one off board and better than any 3rd party supplier. Requires no computer or software or arguing with autorouter and keeps the brain in good working order.

Now I have to wait until Tuesday for parts from RS as I thought I had some 74HC00's in stock

Result so far.

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FR2 board is from Tayda is is glorious to work with.

Last edited by MrBungle; 1st May 2017 at 10:42 am.
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Old 1st May 2017, 11:36 am   #2
mhennessy
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Default Re: More homebrew computerless PCB progress

Looks really good

For simpler stuff - no DIL packages - I quite like the scalpel+heat method. Having drilled the holes, cut around the tracks and remove the excess using a soldering iron to soften the glue. For a prototype in a hurry, it works well. For example: http://www.markhennessy.co.uk/articl...xperiments.htm

Years ago, I used to etch the prototypes for the company I was working with at the time, and really quite enjoyed the process. Now the kids are growing up, I'm tempted to try it at home. Yes, I know that it's incredibly cheap to have a PCB made professionally these days, but there's still something really satisfying about doing it yourself. Apart from the drilling. I hate that. I use a Dremel with the drill stand that moves about 2mm from side to side as you lower it, snapping the expensive drill in the process - mine had a bit of card folded up to stop that, but still it was a long way off the pukka PCB drill that I used all those years ago.
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Old 1st May 2017, 12:20 pm   #3
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Default Re: More homebrew computerless PCB progress

Haven't tried the scalpel and heat method. Great for prototypes for certain. Will try that next time I do something suitable.

My Dremel stand is awful for drilling PCBs, or anything else if I'm honest. Wish I had never bought it! I found the quickest way to succeed with it is stick the bit quite far up the Dremel chuck, tape the board to a bit of 2 by 1 and drill dangerously towards your hand holding both the drill and the work piece. Slightly wonky holes but they're good enough.

I'll probably never get a PCB made commercially. It's a risk as you don't get control over the precise production parameters and you have to wait to test it. My last two designs have gone straight to PCB so I don't want to wait to turn around any mess ups
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Old 1st May 2017, 3:20 pm   #4
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Default Re: More homebrew computerless PCB progress

Quote:
Originally Posted by mhennessy View Post
Yes, I know that it's incredibly cheap to have a PCB made professionally these days,
Where? I've never found anywhere in the UK that charges less than tens of pounds. There is a place in America which looks reasonable: http://docs.oshpark.com/services/ but even their price is for three boards so not much good for literal one-offs.

It's not something I'm likely to personally use as producing the CAD files is beyond me and doing it yourself is quicker and easier to de-bug.

I absolutely agree about drilling being the worst part. I always seem to miss at least one which is then a pig to do with a load of components already fitted.
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Old 1st May 2017, 4:00 pm   #5
MrBungle
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Default Re: More homebrew computerless PCB progress

That's where I am as well. I spend the entire day stuck in front of the PC so I don't want to spend the evening arguing with KiCad and making sure I've done all the DRC stuff and all that.
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Old 1st May 2017, 4:15 pm   #6
David G4EBT
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Default Re: More homebrew computerless PCB progress

A decent drill stand is essential for anything but basic PCBs, as is a magnifying lamp. The more holes, the more DIL IC pads, the greater the risk of skidding off the pad. This is made worse if using PCB CAD software which has small pads and thin tracks, which just doesn't lend itself to home-brew PCBs.

The Minicraft drill stands are very good, but no longer made, though they often come up on eBay. Alternatively, the Expo one is very good too. Dremel stands are the work of Satan. Dire - just so much play - you can move the drill back and forth with your fingers.

Most Dremel drills and their clones only go down to 10,000 RPM which is very fast for PCB drilling, and with more than about 1cm of the bit protruding it will whip about, will e difficult to centre and will tend to skid. (The '4,000' goes down to 5,000 RPM). A small PCB drill is much better from my experience, which is what I use, with a home-brew speed controller.

The dilemma is that for only the occasional PCB, it's hardly worth gearing up with equipment, which can be quite costly. If you wreck a simple PCB, it's no hardship.

These are good little drill stands:

http://www.anticsonline.co.uk/925_1_2371821.html

I've mentioned before that I only use HSS drill bits at 10p each and discard them after one PCB or thy risks skidding and bring up a burr. Tungsten carbide bits last longer and have the merit of a larger diameter shank, so will fit in a normal bench pillar drill. The only downside is that they snap like carrots.

All good fun!
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Old 1st May 2017, 4:21 pm   #7
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Default Re: More homebrew computerless PCB progress

Sneakily this is why I drill the holes first. It's easier to make the pad for the hole than the hole fit the pad
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Old 1st May 2017, 4:33 pm   #8
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Default Re: More homebrew computerless PCB progress

If you need a large area of copper-far easier to place a copy of the PCB layout on board, over a sheet of carbon paper and highlight the non coper areas. Mask if needed the edges of the area and cover it with a couple of coats of clear/translucent Nail Polish. When dry, using a sharp implement- remove the varnish.
My one and only PCB drill was an old dictation tape motor ,with a push switch and used a 2/5 A connector as a chuck. I used a small panel pin as a centre marker.
Mr B- I've found that one of the manual tile cutters ( place tile under cutter and mark ) give a good straight line. on laminate. ( Haven't tied this on fibre glass ,(yet). Then it's easy to cut with tin snips . Must admit I've only done this on a 4 inch wide board ,but it was a good clean ,EASY cut. .

Last edited by Oldcodger; 1st May 2017 at 4:41 pm.
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Old 1st May 2017, 5:43 pm   #9
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Default Re: More homebrew computerless PCB progress

Quote:
Yes, I know that it's incredibly cheap to have a PCB made professionally these days,
Where?
Surprisingly (!) from China, they are of very good quality. Takes a couple of weeks.
 
Old 1st May 2017, 6:23 pm   #10
MrBungle
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Default Re: More homebrew computerless PCB progress

That's 13 days longer than my attention span
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Old 2nd May 2017, 9:58 am   #11
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Default Re: More homebrew computerless PCB progress

Nice work MrB. I don't bother with etching but just use a very fine cutting tip in a dremmel to cut around the traces. It's possible to do DIP packages this way. For HV, high current I go down the cut lines with a bigger tip and also put slot's in, around a bridge rectifier say.

Sand with 1000 grit W&D then do a good visual looking for burrs shorting traces. It's possible to knock up a PCB in an afternoon.

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Old 3rd May 2017, 4:59 pm   #12
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Default Re: More homebrew computerless PCB progress

Interesting idea with the cutting tip. May try that - good for SMD prototypes I assume as well not that I can be bothered with that.

I received my 74hc00's when I was out and finished the board off about 30 minutes ago when I got in. Finished product.

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Turns out I fudged the crystal loading calculation so had to up the load capacitor to 33pF instead of 22pF as I couldn't trim it. And now works pretty well

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Now to age the crystal a bit and my broken IB-1100 is no longer broken. Nixie tube glory
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Old 3rd Jun 2017, 7:54 pm   #13
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Mr B- I'm in the final stages of my lightbox, a long outstanding project,. I've got all the bits, and slowly, but surely I'm putting it together. When i get it together, I will offer it up as a project for others to construct.
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Old 3rd Jun 2017, 9:22 pm   #14
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Default Re: More homebrew computerless PCB progress

Quote:
Originally Posted by MrBungle View Post
I'll probably never get a PCB made commercially. It's a risk as you don't get control over the precise production parameters and you have to wait to test it.
I agree that the waiting is a pain. But the control over the production parameters? Anything from a commercial PCB house, even the very cheapest, will be at least ten times more precise than what can be etched or engraved at home. The holes will be in the right places and they'll be the right sizes, and the tracks and gaps will be the thicknesses given in the PCB file, as long as they're within the design rules for the PCB house. Oshpark specifies minimum 6 thou track and gap, which is good enough even for pretty demanding surface mount PCBs. That's typical of a run-of-the-mill modern PCB process.

In the day job I get quite a lot of PCBs made. It's incredibly rare to have a PCB manufacturing fault occur and get all the way back to me. Far more common, actually, is for the manufacturer to silently correct errors in my design: things like silk screen markings overlapping pads, the occasional bit of stray copper that the design rule checker didn't catch, that sort of thing. Several times I've been debugging a board and found that it didn't quite match up with the original CAD files: it got better between leaving my computer and arriving back as a manufactured board!

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Old 3rd Jun 2017, 10:48 pm   #15
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Default Re: More homebrew computerless PCB progress

when I say production parameters, to be clear I'm talking about getting non silk screened and non solder masked boards for one offs. Absolutely no one on the budget end will sell you those. The rationale being for those boards is it's considerably easier to "x-acto and kynar" a cock up when there's no solder mask then rather than wait another two to four weeks.

If I was doing anything even semi professional it'd go to a board house and go through design rules properly.
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Old 4th Jun 2017, 9:27 pm   #16
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Default Re: More homebrew computerless PCB progress

Hi peeps....I understand the need to make cheap / quick pcb's,, but if you are making a serious project.... "one off" prototypes in simple methods as described above are very counter productive, as changes are ... in my experience..always necessary.
Thus I always use a cad program... and the photo resist method.
My latest light box is attached and works very well, the UV tube box has been retired.
The leds are UV of course and the matrix is 18 leds X 14 rows... the timer was from Ebay.
The case was from Maplins...... about a tenner I think. 4mm glass.
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Old 5th Jun 2017, 8:52 am   #17
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Default Re: More homebrew computerless PCB progress

Wendy

That's very smart UV box indeed - do you have a link to the LEDs you used?

I converted an old flatbed scanner to UV using parts from a UV lamp (iirc it was one of those SAD lights) but the tubes have seen better days and an upgrade is on the cards.

Also, what CAD software do you use? I've been trying to get familiar with something (anything!) recently but always find that the software has far more functionality than is required for most projects and, as a result, makes for a complicated operating method.

'Back in the day' I used a PCB program that was as basic as 'select the pad size you want', 'place all the pads', 'select the track size you want', 'join the pads'!!! Print! EZPCB I think? Either way I'm almost down to using MS Paint with pre-designed pads but would like to use something that at least offered a 'snap' function so I can place things with more accuracy!

Any recommendations?
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Old 5th Jun 2017, 9:52 am   #18
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Default Re: More homebrew computerless PCB progress

That is rather nice actually. Good idea with the UV LEDs.

Last PCB design software I used was Protel Easytrax, followed by Eagle. I really liked the former.

Edit: Turns out you can still get Easytrax! http://www.lupinesystems.com/easytrax/
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Old 5th Jun 2017, 10:44 am   #19
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Default Re: More homebrew computerless PCB progress

Hi Kelly's eye.
I must admit...... I bought Diptrace...... I used to use Protel Pro, until it did not work on Win 7..... no printer drivers.
The UV leds were from Ebay...... just looked back and that item is no longer available... but just search UV Leds.....and buy a reel. VERY easy to install....just cut each length and uncover the terminals to re solder.
The timer was a module from ebay..... With the timer module.... who ever designed them.. had no conception of fitting to a panel... I removed the relay and terminals and re soldered on the other side of the pcb.
Re Diptrace........ The basic version is 500 points and two layer.... I bought an upgrade that allows 8 layers and 1000 points...
You can download a 30 day trial.
I really "loved" Protel...... I had an unlocked version from Romania.... but as I say it will not or would not drive a laser printer.
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Old 5th Jun 2017, 12:48 pm   #20
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Default Re: More homebrew computerless PCB progress

Makes my box look a bit Heath Robinson. Tubes -I got from THAT on line place , as most of the rest. Starters from Asda ( now realise they were a bit expensive), starter holders are bit expensive in RS ( pack is £5 for 10), and on line, but I managed ( in true Vintage style) to acquire some from old scrap lights. Case, I made myself, from MDF .Local place will cut to size, if you buy a half sheet.
PCB software - I've got a copy of Express PCB ,which I quite like, and a copy of PCB artist, which I admit I haven't given a chance.
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