My Relay Computer - First Experiment

I’m working on constructing a computer using relays. This video shows the first three cards in operation. The top card is the adder/incrementer, the second is logical and ALU control, and the bottom one holds 4 x 8-bit registers. Red lights are data bits, blue are control lines. The control lines are driven by a PC through the smaller relays on the small card at the very top. This first experimental cicuit iteratively increments the value in the “A“ register (the row of LEDs at the top-left of lower card). The operation is as follows: 1) Select increment operation of ALU (shown by blue LED on the top card) and select A register as input. A 1 appears on data bus. 2). Store data bus in B register (bottom row of LEDs on bottom card). 3). Load B register onto data bus. 4). Store data bus in A register. 5). Repeat from 1. Watch the binary value of the bottom LED rows increase by one and enjoy the beautiful sound of the relays clicking! My intention is to extend this into a complete, micro-programmable CPU. Read more at !