Wire-Wrapping Milestone!

A project log for Open Source DSKY

Modernization of the Apollo Guidance Computer

viva-penguinosViva Penguinos 07/12/2014 at 07:270 Comments

Many things have been accomplished since the last project log. Because of this, I'm going to split this into two project logs. A week after I posted my last project log, I finally received my shipment of 30 gauge wire from china. The order was divided into two packages; the first package just had just a spool of red wire (Not the color I wanted at the time). Unfortunately, the spool was damaged during transit, but I'm not going to complain about it. The 2nd package contained the other 3 wire-wrapping spools I needed. Here’s a picture of the entire spool together (Yes. That is a CD/DVD spool.)

Hello World!

When I received my wire-wrapping wire, I was anxious for the other package to arrive (I didn’t know when it was going to even arrive, it actually took 2 weeks to arrive). Until then, I used red wire-wrapping wires to just see if I wired my IC and resistors correctly. Here’s how the wire-wrap looks for the first 7 segments. The cable is a mess but I did not intend on making it look clean.

The more wire I added, the larger mess it became.

Until the last 7 segment display for R3 was finally wire-wrapped.

It looks like a small spaghetti monster; I connected my cathode and double checked all my pin-outs from the resistors. Additionally, I verified that all of the IC could handle the same voltage supplied (5V).I plugged in my microcontroller and looked at the 2nd perfboard. This was the sight I was greeted to.

Hello World!

The process of having an idea from a concept to an actual prototype is one of those feeling that is hard to explain. Seeing that 7-segment LED light up saying “Hello there!” just kept me going to completion. As much as it pains me to remove all wire-wrap, the 2nd package arrived which contained the orange wire-wrapping spool. But before I took it apart, I made sure I wrote all the pin outs for the 7 segment and verified it with continuity so I could just wire-wrap without going back and forth.

More Wire-wrapping!

Since the first row of 7-segment worked, I decided to just wire-wrap the project in one go. Knowing that Murphy’s Law may strike again, I went and wrote all the pin-outs where the shift-registers connect to including the pins on the 7 segment drivers. I Doubled/Tripled checked the pin outs with continuity before I continued. This would be the last time I have a known working configuration. If I screwed up here, it would be a major hassle to fix the problem should it not work. I call this, Murphy’s sticky note.

I continued with wiring R2’s shift-registers tying with R1 shift registers. The white wire-wrap indicates shift-registers to BCD decoders. The blue indicates BCD decoders to resistors. I used a spare wire-wrap IC to make sure all the wires are routed in the proper way.

Here’s the front side of the perfboard. Remember that each shift-register can accept 2 BCD decoders. So I have 5 shift-registers driving 10 BCD decoders each powering one row of 5 7-segment displays. The amount of repetition I have to make is astounding. But headphones and having music makes this relaxing.

Wire-wrapped R3’s 7 segment displays, this was one of the trickier one to place since it overlapped both R1 and R3 wire bundle. I quickly learned that the toothpicks from wallyworld fit nicely between the pins. After spending some time wrestling the wires, I managed to complete it.

Here’s the top side of board. Note the placement of one set of resistors. It's placed differently because R2's wire bundle is in the way. Refusing to re-wrap R2 again (Yay Murphy’s Law!), I decided to just suck it up and place it in a way where I could make the other resistors look somewhat consistent.

Here’s a close-up of some of the wire-wrapping job, more “artistic” images below!

Unfortunately (For my readers, a relief.), the images I have for the Verb, Noun, and Program numbers were blurry, or I had forgot to take them (Didn’t take images for Noun, and Program, Verb was Blurry).

Mounting time!

After finishing wiring shift registers, BCD decoders, and resistors it’s time to mount it on a somewhat solid frame so I can move it from different places. I passed by the local craft store and brought 12inx12in birch plywood board (304mmx304mm for metric people). Drilled some mounting holes and doubled up on computer standoff for the proper height. Here’s how it looks like.

I mounted the perfboard backwards so I can work on it effectively without worrying about it moving. Here’s how it looks like during the wire wrapping process.

I still can’t get over how well it looks when you properly route the cable and making sure there is little or no slack. Here’s a close up of it.

I continued wire wrapping the 2nd row and things started becoming more difficult organize. After some trial and error, I found that the tweezers I’ve been using provided good amount of pressure to hold itself in place without bending the pins.

The two images below are close up of R1 and R2 wire route.

I removed the wire wrap IC I used for routing R1 and R2 wires so I can move it in preparation for R3, Verb, Noun, and Program Number. To prevent them from shifting too much, I tied it at certain intervals to make sure the wires are bundled together. Then I proceeded to wire wrap R3’s. I shifted the wire wrap pins by one row so I can have space when I route things, a move that proves to be very useful soon.

Again, I forgot to take pictures of me wire wrapping Verb, Noun, and Program but no drastic changes. Nearing the end when I was wire wrapping the Noun and program, the cable kept popping out of the IC pins because it kept going above the pins. One change I made was moving the connector from a 5 pin to a 20 pin connector so I can make it look like a clean prototype. This again proves very useful when I went to add additional components. Even though it was a pain in the butt to move the connector, I managed to get it assembled.

This concludes the end of my wire wrapping adventure and this project log. You’ll see more in the next project log. It’ll be written up once I release this to the public. I’ll leave you with some additional pictures; A few comments must be made. First is that the keypad and RTC was added a few days later when I was programming and working on it. The next build log will contain mostly code and what features I’ve manage to get working (maybe a video? :D).