Barry's Coilguns

Breadboard for Timing Electronics

How do you build the electronics for timing, counting and comparing? How can you make it easy to modify? What did I build, and how did I arrange things?

Breadboarding Electronics

The easiest breadboard to use for IC's is the push-down pin array. You just press the hookup wire into the holes, and each group of five holes in a row are connected underneath. It's sold (at a rather high price) by Radio Shack and (at better prices) other places.

My breadboard is mounted on an aluminum box that also carries a 5v supply for TTL. It has sixteen LEDs with Darlington drivers along the right-hand side for debugging logic circuits.

Breadboard Photo

Photo of breadboard, with parts labelled

Breadboard Wiring

There are three sections of breadboard side-by-side, with longer thin strips for power distribution along the bottom.

The long gray cable for "timing control output" goes to the business end of the coilgun. It is an eight-wire cat-3 cable leftover from some telephone re-wiring at home. It has color-coded wire assignments of:

green/white coil #1
blue/white coil #2
orange/white coil #3
brown/white (spare)
white/orange trigger
white/blue trigger
white/brown ground
white/green ground

Comparator Wiring

There are three 8-bit comparators, each wired to a pull-up resistor block and an 8-bit DIP switch. The wiring gets a little messy in this area, with all the 8-bit buses running around. So here's a diagram showing the pin connections between the chips, and notes about which switch does what. All four comparators are wired like this. Diagram of wiring switches to comparators

Note the switch is labeled SW8 = LSB, because the engraving on my switch block says '8' but the wiring is connected to D0 which is the least significant bit of the counter.

Note the switch says On = "0", because again the engraving on my switch block says "On" but the wiring corresponds to a logic 0. Sorry if it's confusing, but it seemed easier at the time to orient the switch this way. I trust you will find a more sensible way than I did for this portion!

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