Eric HertzIn the last log was a TODO:
TODO: Believe it or not I did all that layout without actually verifying the chips I have match those footprints. Usually that'd be the *first* thing I'd do... Usually I'd make my own, in fact, because I rarely trust those provided. This time, for some reason my brain's been on this tetris-style packing-kick. Could be risky. I guess we'll see. I can feel the datasheet-lookup energy building... may be a few days. Or maybe I'll just print the danged thing and set my chips on the printout.
Whelp, I printed it out... and it turns out it was risky.
Out of 7 footprints I chose and laid-out, only 3 were correct.
The 20-pin 7400-series SOICs in my collection are *wide*... Easy enough to fix since it's laid-out on breadboard.
The 56-pin SSOP is 0.5mm spacing, not 0.4mm... Whelp, that was a lot of work for nuthin.
The clock-generator chip is actually SSOP-10 (?!) not SSOP-8, and... I dunno what spacing, smaller than 0.4mm, it seems.
........
I suppose I should take a step back and re-evaluate this ordeal... Maybe I'll spend a few days cleaning the apartment, first.
Or maybe I'll just go play some Tetris... My gameboy's long-gone, and I'm tired of staring at the TV/monitors... I hate using my phone's touchscreen for things like this...
But I just happened to save one of those ridiculous cheapo hand-held games from the 90's with the custom LCDs, and it just happens to have Tetris on it... Time to dig out the file and scouring-pads and dig through the box of batteries.
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Yeah, that sucks. I have a small pile of almost-useless boards with footprints from downloaded Eagle libraries - someone used a bottom view to draw footprints for a few SMD parts, so they're reversed. The bad footprint was for a SMD crystal, so I can run these boards with an external oscillator piped in, but it's still lousy.
I'm a big believer in the print-and-fit method, too. I used to glue the prints to cardstock and punch holes with an awl to make sure through-hole parts fit back in the day. With the parts stuck in there, I was always tempted just to wire it up right on the cardboard :-)
In the crystal case, I was trying to save time by ordering parts at the same time as the PCBs.
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Haha! Soldering-up on cardboard! Maybe a few tiny pieces of breadboard material at each end of larger packages to clamp 'em in place... or just bend 'em over... Hmmmm.... The SMTs not so much, but then there's this (from the blog a while back):
No need for kapton-tape when using cardboard... (or does cardboard caramelize?)
Been debating whether unwinding a transformer/motor would leave the insulation intact. A couple different ones for color-coding...
Slightly easier and more-stable than cardboard, I do have a huge piece of perf-board (no copper)... I've found it pretty difficult to use with through-hole parts, since the only bond is between the wire and the pin, and the perfboard acts as a soldermask... and significantly more difficult when you've got to solder up multiple wires to the same pin. But maybe extra flux, and pre-tinning before inserting would help. Or, again, underlay it with breadboard only where the pins stick through. Hmmm...
Or turn those chips (in the photo) upside-down and "ugly" it on regular-ol' copper-clad... hmmmmmm...
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I made a wiring pen a few years ago for doing this sort of thing:
It was based on one of Alan Yates' blog posts:
http://www.vk2zay.net/article/208
he also looked at the solderability of various wire coatings:
http://www.vk2zay.net/article/209
Mine is tricked out with a grippy pen barrel felt washers regulating tension on the spool.
I have used wire from an old fan motor and various transformers for winding inductors; the insulation typically survives, but I have yet to find one that uses solder-though insulation (it may be forbidden in line-powered magnetics?). I've had better luck with ebay, although not 100% success. I bought 3 colors of 28 ga wire for winding HF transformers, and while two of them tin with the iron, the third has to be scraped :-(
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@Ted Yapo, nice pen, and great info... hadn't even occurred to me there might be enamel that won't burn off. I wonder if one of those butane torches would do it, though I'd imagine flux/solder is a big part of keeping the enamel from just turning to crisp right where it's at. Guess I've some experimenting to do!
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