Bug Robot from an Old Toothbrush

A classic kids' craft workshop staple, but here we go...
Stick a vibration motor on an old toothbrush and make a bug robot.

It comes together in no time, yet somehow never fails to impress.
Perfect for reclaiming your dignity as a dad.

Here's what the finished product looks like:

Parts

Just a toothbrush, a vibration motor, a coin battery, and some cellophane tape.
The key is to build it the moment the toothbrush is done — so keep a stock of motors and batteries on hand.

Vibration Motor

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A micro motor with an offset weight for vibration.
The lead wires are extremely fragile and often snap during handling.
They can break during shipping, or during installation — they'll die at every possible moment.
Budget for a few failures. If you're lucky, you can find 10-packs at quite a low price per unit.

Coin Battery: CR2016

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A coin battery for electronics tinkering.

It's exactly half the thickness of the commonly used CR2032.
Each cell is 3V, so two stacked together make 6V — enough to drop them into a CR2032 battery holder and power a 5V microcontroller like an Arduino. Handy trick.

For this project I'm just taping it directly to the toothbrush — no holder.
Thinner means less capacity; with a micro motor attached, it drains in about 5 minutes.

A single cell costs ¥100 at a ¥100 store, but buying in bulk on Amazon brings it down to about ¥40 each.

CR2032 works fine for this project too.
If you want the batteries to double as stock for calculators and other normal devices, CR2032 is more versatile.

How to Build

(1) Cut off the toothbrush head with pliers.

(2) Trim the bristles at an angle with scissors. The angle determines how it moves.

(3) Tape the vibration motor directly onto a coin battery with cellophane tape, then secure the whole assembly to the back of the toothbrush handle. Done.