Mar 16

Mar 16 Building Lego Logic Gates

Before starting to build a universal Lego logic gate, be sure your understanding of logic gates is solid. Click here to read about the design process and the breakthrough that led to a single logic gate that can mechanically represent all two-input logic gates.

Ready to build? Here's how we'll proceed:

Use a knob wheel to position axle and cams at four unique positions.
- For Lego, four positions is easiest but for 3D printing, six would be better.
- Six positions is possible with Lego, but it's bulky and would involve gears.
Use a rubber band "click" to force exactly 1/4 of a rotation.
Attach two cams (1x2 lift arms) on knob wheel axle to lift logic output arm.
Use tow ball in a 90 degree angle connector to engage knob wheel.
Use axle lever handle to simplify input and weigh the input so it doesn't change.
Design output lift arm so most of the weight is pushing it down. This will reset the output to down using gravity.
Use stops to keep inputs and output from traveling too far: base, 2x8 block, and axle 1/2 bushing are used.
Use the movable 1x2 lift arm to create two different sequences to cover all gates (0011) and after switch (0101).
Build the model in a skeleton style to show all components.
Include a pointer to indicate which gate is being modeled.
Include an optional guard to prevent two inputs being moved at one time.

Download the parts list, and let's get started.