This is the first prototype of simple calculator that can add 4-bits.
Green and blue leds are input registers I can switch with a buttons in the middle. Output register are red leds and the most left one red is carry out.
The chip I use is 74HCT283
Pull down resistors are 4.7K (VCC is 5V)
At the moment I can only add.
In future I’ll implement subtract multiply and divide functions