What is it?

A half-adder is a digital circuit capable of summing two binary digits to form the sum, and a carry. For example, using binary notation a half-adder will compute the following binary relations:

0 + 0 = 0

1 + 0 = 1

0 + 1 = 1

While:

1 + 1 = 0 and a carry

That is a sum of zero and a carry of one. The half-adder forms the basic unit for building much larger and complex adding circuits and can be built from five NAND gates. The kits comes complete with all parts to build a fully functional half-adder. The only thing missing are four 1.5 v batteries. Parts include five NAND gates, jumper cables, breadboard, battery pack and two input switches to represent the binary inputs. Each NAND gate displays its state via a LED, it is therefore possible to easily get an idea of the state of all the gates simply by inspection.

The kit also comes with a detailed manual on how the individual gates operate, how the half-adder operates and full assembly instructions making it suitable for beginners. With two kits it is possible to make a full-adder (see manual).

Why did you make it?

I am interested in retro computing and having built a half-adder from elementary transistor gates. I thought it would be worth making it available as an educational kit.

What makes it special?

This kit will help users understand transistors, logic and simple binary addition in a single kit.

Specification:

• NAND Gate Board Dimensions: 1 inch by 1.1 inches
• Input voltage 4.5 to 9 Vdc
• 3mm (M3) screw holes at the corners
• Pin connectors are spaced such that the boards can be optionally plugged into a breadboard

What's in the box?

• PCB Board x 5
• Four 2N3904 transistors x 5
• Four resistors x 5
• One capacitor x 5
• 1 x three pin connector x 5
• 1 x four pin connector x 5
• 3 mm LED x 5
• One breadboard
• Two tactile switch kits
• Two resistors for pull-down (yes pull-down) logic input
• Jumper cables to make half-adder
• Battery pack
• Twelve page assembly and how it works manual

NOTE: This is a kit that requires basic soldering skills.