Reconstruction of the Z3 adder

The addition circuit of the Z3 as an interactive demonstration object:

The addition circuit of the Z3 as a poster with additional information on the Z3:

The mantissa addition circuit of the Z3 was built on a DIN A3 sized board for exhibitions and lectures about Konrad Zuse.

According to the original documents a 10-bit electro-mechanical circuit was developed. It consists of two manually settable registers to enter the summands - this was realized just as in the original using bistable relays - and of two XOR gates and a AND gate per bit for the calculation of the carry-over. The entered summands, all intermediate data of partial operations and the end result are displayed with LEDs.

In the same manner as in the original machine each calculation was divided into three steps that can sequentially be triggered with a turning knob. A switch allows to choose between addition and subtraction.

Acknowledgment: We like to thank the electronic laboratory of the Fritz-Haber-Institute (MPG) especially Georg Heyne, Wolfram Däumel and Viktor Platschkowski for their advices, the use of their layout software and the digital milling machine.