Modular Input
I have been busy hacking and designing, organizing Making Lab and SFPC, I haven not been able to post as much as I should have. So here is one tail end of a project I’m working on. it’s a input device for modular computer.
It has two sets of 4 stay put switches, 2 individual switches and a set of 4 tiny DIP switches. This is ideal for ALU input. and also for 4 Bit Adder/Subtractor. Earlier prototype used 8 switches which is easy to connect but confusing, because it does not show numbers on hierarchical manner. It’s 1,2,3,4 and 5,6,7,8. where as I wanted
1/2/3/4
5/6/7/8
Above image is the breadboard of ALU. ALU does math and logic for most common and uncommon computation in primitive computer. More on ALU on the next post. You can see the DIP Switch is placed upside down, to make it easier to connect to ground. And thus the printed numbers count backward, making it very confusing at first.
So it was time to make my own input module!
I’m using hair thin AWG 34 Teflon wrapping wire. It’s very thin.
Routing input keys into the bus. I used tiny U shape wires to make wire traffic less of pain.
Halfway through the work. I see I have all the inputs and no grounds connected. Due to character of TTL chips I’m using, usual state is HIGH and I only need to ground to LOW. 
The hardest part of debugging was one of this switch. It wasn’t soldered well in the beginning.
It took about two hours. I thought if there are any smarter way of routing the input, so it will be easier to map in the counterpart module, say ALU unit. but decided to stay true to the spirit of modular computer and went from fart left pin toward the right in the order of left bottom switch to right most switch. It may be less confusing to be a bit dumb in the end. 
Nice sunshine at 7th floor of MEX. Vibe is very nice here. All hackers and makers. Thanks for being welcoming.
I’m not proud of the goo on top right corner. I might need to rework it. 
Everything works so far. Debuggning was relatively painless because the wires are so thin, and easy to reroute. I was skeptical of this wire because its too thin and flimsy and easy to break. but if you solder an end, wrap it around and solder again, it can be pretty sturdy. Also if you don’t mix it with thicker wire in the same circuit, it’s less likely to get beat up and fall apart.
I will probably add a LED to signal it’s working. I left some space in the edges to put a potentiometer and also put more output, because the main switches are all DPST (Double pole single throw)each two independent switches (all ground, voltage and signal are unconnected from another set in the same switch) .
More coming very soon. Next post will have more computational elements. Maybe Adders or Memory units.
So I’ve been hacking in and out of my apartment. some days in YESYESNO studio and recently in Math Practice Office in DAMM33, MEX, thanks friends!
7.17.2013
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