Reciprocating Rack and Pinion

Learn how to create an automated geared mechanism with hypnotic motion. Use the Adafruit CRICKIT and Circuit Playground Express to make it dance! This is a mechanism for converting rotary motion to linear oscillating motion. The gear appears to bounce back and forth as it continuously rotates. As the wheel spins, the gear turns and oscillates between two tracks. It emits clacks and sloshes sound while in motion creating the sense of white noise. The teeth engage the lower track as it rotates. When it has travels the length of the slot, the teeth clears the end of the track and catches the teeth in the upper part of the track.

Make Robot Friend

Use Microsoft MakeCode to program the motor and use the on-board sensors from the Circuit Playground Express to make an interactive robot. This project was inspired by Ron Walters Reciprocating Rack and Pinion mechanism build.

A Black woman's manicured hand holds a round microcontroller with lit up LEDs.
Circuit Playground Express is the next step towards a perfect introduction to electronics and programming. We've taken the original Circuit Playground Classic and...
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Top down view of a Adafruit CRICKIT for Circuit Playground Express with a circular board connected.
Sometimes we wonder if robotics engineers ever watch movies. If they did, they'd know that making robots into servants always ends up in a robot rebellion. Why even go down that...
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DC Gearbox Motor - TT Motor with two long wires and yellow body
Perhaps you've been assembling a new robot friend, adding a computer for a brain and other fun personality touches. Now the time has come to let it leave the nest and fly on...
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Angled shot of 3 x AA battery holder with 2.1mm plug. There are three AA batteries in the holder.
Here's another addition to our growing family of AA battery holders. A holder for three (3) AA batteries!...
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We'll need just a 3xAA battery pack to power our CRICKIT robot. 

1 x 3 x AA Battery Holder
Battery Pack with 2.1mm Plug


You'll need some extra hardware like machine screws, nuts and threaded inserts to assemble this project. They're linked below, but feel free to source them from your favorite supplier.

2 x M3 x 20mm Metric Machine Screws
For mounting the motor to the housing.
6 x M3x 16mm Metric Machine Screws
For bolting the tracks, base and feet together.
3 x M3 x 6mm Metric Machine Screws
For the wheel, pin and drive hub parts.
10 x M3 Metric Hex Jam Nuts
For securing parts together.
1 x M3 Threaded Insert – Brass Knurled
Heat press insert to center pin for drive hub assembly.
1 x M3 Metric Screw Tap
Coarse Thread Taper Taps
2 x Goggly Eyes
25mm (1in) diameter – Assortment Pack

Prerequisite Guides

There's resources in these guides that go beyond what's covered in this tutorial. MakeCode guide is all about setting up your Circuit Playground Express board. TheCircuit Playground Express introduction guide walks you through all of the pinouts, sensors and everything you need to know.

This guide was first published on Aug 08, 2018. It was last updated on Mar 08, 2024.

This page (Overview) was last updated on Mar 08, 2024.

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