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Showing posts from May, 2014

Register Construction: Completed B and C 8-bit Registers Full Test

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The B/C Register card is now complete and looks like this:
As usual I've put a video together which demonstrates this card in operation ... firstly on its own but then together with all the other cards constructed so far. Hopefully these videos are 'adding value' and are worthwhile (they really do take ages to put together ... this one took about 5 hours effort in total for 20 mins of video). Please do leave any comments, good or bad, either here on the blog or on YouTube against the video or feel free to ask any questions about the computer as although I know this is a pretty niche subject I can't help feeling I'm talking to myself ;)

There's just one more card to go now before the first card bay is full ... the A/D register card. This will effectively be a duplicate of this card but without the B/C ALU feed lines and so should be a little quicker to construct. Once complete it should be possible to do some running calculations with the ALU by hand and this wi…

Register Construction: B and C 8-bit Registers

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As mentioned in my last post I decided this time around not to post after each stage of card construction (being as the construction steps are now pretty similar to those for previous cards). In line with that decision this post covers all the steps taken to construct the B/C register card ... primarily in photos and then with extra text where anything odd or different came up compared with the other cards completed so far.

The first step was to solder down the LEDs, ribbon cable sockets, relay sockets and finally the wire wrapping posts. Here's some pictures, front and back, of the card following this round of soldering:
I made a few tweaks to the construction method on this card. Firstly I applied a line of super glue to the board when placing the LEDs to stop them moving about while soldering and this has kept them more or less pointing forward. Also with the LEDs I've removed the negative wrapping post behind each LED to make wiring up easier later on (and to avoid shorts…

Register Design: B and C 8-bit Registers

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In a recent post I put up the design for the A and D 8-bit register card ... the B and C register card is very similar in design but has the additional complexity that it has to directly feed the ALU. In another recent post I covered how to take multiple outputs from a relay without risking back-feed by utilising diodes in the output line. This post therefore brings together those two designs and although it's essentially a re-hashing of the AD card post but with extra bits I'll go through the design as I did with the AD card so that this post stands alone as it were.

So, as before, I'll start with a card schematic of what the main bit relays look like for the two 8-bit registers when placed on the usual 55 x 40 hole pad board (excluding wire links):
Each of the relays above stores a single 1-bit value so there's 16-bits worth in total (which could all be used together if we were making a 16-bit register) or two lots of 8-bits (for our two 8-bit registers). Each of th…

Enclosure Update: Magic Pen

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Just need to quickly share my experience with what I'm dubbing the 'magic pen' before I put up the B/C register schematics (yup, they're finally ready). If you've read my recent posts you'll know I ordered in some laser cut acrylic parts for my enclosure including one part which is engraved as well as cut for the switch panel. Close up it looks like this:
Generally I'm really pleased with this part but the engraved text looks scruffy and there's quite a lot of laser smudge marks around the text so I had a dig around the internet seeing if there's any 'post-processing' I can do to the part to clean it up a bit. I ended up settling on cleaning up the perspex with a special cleaning fluid (never clean acrylic with anything else) and then infilling the text.
The cleaning fluid I've gone for is the Meguiars PlastX sourced from Amazon and after trying on a piece of scrap acrylic to make sure it doesn't eat it I cleaned up the switch panel …

Enclosure Update: Fitting of Laser Cut Parts

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I was going to spread the fitting of the laser cut parts to the lower enclosure over a couple of evenings but in a fit of geeky excitement I ended up doing it all in one evening. Fortunately I didn't damage anything in my 'rush' (although I had to accept a few niggles) and it went something along this lines of this ...

First job was to fit the panels in to the front and rear door frames. As is often the case with these things I had this picture in my head of the panels popping straight in the frames with no fuss ... a picture which always seems to differ substantially with the real life experience. To say this thing was a tight fit is an understatement. I started off with a U shaped frame and the idea was to slide the panel in from the top but as the panel moves further down it builds up more and more friction resistance in the plastic panel holder strips. In the end I took the frame apart and built it back up again around the panel but even with this it certainly took so…

Enclosure Update: Laser Cut Parts Arrived

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I've been looking forward to this moment for nearly a month ... the laser cut parts I ordered to move my enclosure construction forward have finally arrived.

So, let's start with the unboxing: The parts came in the same sort of packaging that Amazon tend to use for delivering books, DVDs, etc and it looks to have kept everything in place securely and fortunately those plywood parts don't appear to have been scratching the hell out of the acrylic ones.

I'll run through all the parts in the package and first up is the plywood floor/ceilings:
The picture on the left is viewing the part from the top side and the one on the right from the underside. The part was cut with the top side facing up and so the bottom side has picked up plenty of burn marks which is reasonably inevitable when cutting plywood with a laser. The odd hexagon shaped burns on the underside come from, I think, the cutting bed which has a lattice structure with this shape. All of these burn marks can be c…