binary adder

I designed and built a binary adder which doesn't use any transistors or semi-conductor. I only used solid state relays, leds, switches and resistors. The idea was to built something similar to the early computers.

When I designed this calculator, I didn't know the theory behind circuit design. I also didn't know that boolean algebra was linked to computing. I therefore designed this calculator by using intuition and a lot of trial and error (on paper). One of my main challenges was to reduce the number of relays needed, as these components consume a lot of energy and are expensive.

front side

The basics of any calculator lies in the ability to do binary calculations. Binary is a different way to represent numbers. Since we have ten fingers, we count in a decimal system. We count from 0 to 9 and then start again from 10 to 19. We count by groups of tens. 25 is two groups of ten and 5 groups of one. Unfortunately computers can't calculate like this. They can only count by groups of twos, so 101 is one group of 4, zero group of 2 and one group of 1, which makes a sum of 5.

keyboard

To do the basic binary calculations, I used relays. These are little switches that aren't controlled mechanically like a keyboard, but by electric current. When the current flows through them, they will close (due to electromagnetic interaction). When the current stops to flow, they will open. You can see the three relay on the picture above (up on the right).

back side

The first part of the project was to draw the circuits on a sheet of paper. This was interesting because I didn't know how many relays I would need; my first design required eight of them. I then reduced the number to three.

Then I ordered the components and soldered them together. The major difficulty I encountered was working with all the wires.

sample calculation: 15 + 5 = 20

• inside the binary adder (ppt, includes circuit diagram)
• Binary numeral system (wikipedia article)
• Relay (wikipedia article)