Meet the Dimebots: Self-Contained Micro-bots the Size of a Dime
Chris Stemple built these tiny bots with a repurposed pager motor, an ATtiny1614, a LiPo battery, and o-rings.
When you think of a robot, you might envision a large, complex contraption. However, Dr. Chris Stemple's ingenious Dimebots are a different construction. These micro-bots, about the size of a dime, are surprisingly simple and easy to build with readily available parts.
Stemple crafted the clever little micro-robots with a tiny motor, LiPo battery, proximity sensor, and a microcontroller. They weigh only five grams and are about the same size as a US dime (about 18 millimeters), hence the name Dimebots.
A Microchip ATtiny1614 microcontroller runs the robot. Stemple initially considered the Microchip ATmega328P, the same eight-bit microcontroller used in the Arduino Uno and Nano boards. However, the ATtiny1614's SOIC package offers easier soldering and a single-pin Unified Program and Debug Interface (UPDI), which saves space on the custom printed circuit board and reduces the build cost by not requiring a specialized programmer. For example, you can create a UPDI programmer with a USB-to-serial cable and a single (10 kilohm) resistor.
An optical sensor positioned on Dimebot's front provides "vision." It is a Vishay VCNL4040 proximity and light sensor. These infrared-based sensors, with their built-in signal conditioning and I2C communication, seamlessly integrate into projects like Dimebot. They can detect ambient light and, more crucially for a robot, determine its proximity to a wall or object, enabling the bot to navigate around obstacles.
A 30 milliamp-hour battery provides energy for Dimebot's electronics and a 4 x 8-millimeter motor. Stemple repurposed this mini motor from a pager's vibration module. According to the motor's datasheet and the battery's capacity, Dimebot's runtime could reach up to an hour. The motor's 70-millimeter shaft attaches to the drive wheels.
The drive wheels have two major components: a hub and a tire. Stemple 3D-printed a hub that attaches to the motor's shaft and a "tire" made from 005-sized o-rings. The freewheels, made from an off-the-shelf ball bearing, also use the o-rings as tires. Stemple lightly sanded the o-rings to increase their traction.
You can download the MIT-licensed Eagle design files, 3D-printable parts, and sample Arduino code from the Dimebots GitHub repository. This project description provides additional detail on why Stemple chose specific parts.