8 bit Computer
July 24, 2014
front view
This is my 2nd try of a full adder. It is made out of 600 SMD components, parts got silver plated and consumes about 2 A.
It handles negative / positive numbers and can add or subtract them.
274 SMD NPN transistors, SMD resistors (10kΩ and 1kΩ) and 0 Ohm bridges are only a small insight into this huge project.
side view
For this and following Projects, I used the NOR gate standard and called the FA: 4.3
NOR gates are very cheap to build, because they only need one transistor. However, they are still very tricky. Some diodes would help to control the current flow. But this is an other lesson.
The first necessary part (for hardware-subtraction and choosing) is the XOR gate:
xor schematic
xor brd
The second part is the adder itself:
FA schematic
FA brd
The third part is the half adder. (Which are used for the "Add 1" command):
Half adder schematic
Half adder brd
This is the board which splits the binary number to the sign and a positive number.
splitter brd
The interesting looking main board, which connects all components:
main board brd
Complete circuit:
top view
input output board
output board
Back view of the hole thing:
back view