Two sensor assemblies to measure two different motors
5V operation
The HC-020K motor speed sensor module has three main uses.
The first is to determine the speed of rotation of an unknown motor or a motor being driven at different voltages or PWM settings in a bench-top setting.
The second is to mount it permanently on a robotic vehicle to provide a means to measure the speed of the vehicle and to detect if the vehicle has stalled or is straining to rotate the wheels and therefore adjust the drive to the motors. These sensors are usually mounted on the two drive wheels or 4 can be mounted for a 4-wheel drive vehicle.
Use it to measure something that rotates around a shaft which is not a motor. With this sensor and knowing the circumference of your hamsters wheel, you can finally figure out just how fast that little guy really is.
The sensor works by mounting the spoked sensor wheel on the motor shaft. The spoked sensor wheel is designed to fit motors with a rectangular shaft of approximately 5.5 x 4mm as is found on the commonly used yellow motors sold with lower cost robotic vehicle kits such as our own.
The U-shaped sensor assembly is then mounted so that it cradles the spoked sensor wheel. As the spoked sensor wheel rotates with the motor shaft, the spokes in the wheel make / break the IR sensor beam and causes the sensor to output a series of pulses with one pulse for each of the 20 spokes in the wheel. An LED on the module flashes for each pulse.
This pulse train is typically fed into an interrupt input on a uC that counts the pulses as we show in the program below. From these pulses, the rotational speed can be calculated and if the circumference of an attached wheel is known, the speed of travel can be calculated.
Module Connections:
The module has just 3 pins for connection, power, ground and sensor output. The right angle header is mounted reversed to minimize the installed footprint.
1 x 3 Header
5V – Connects to 5V on uC
GND – Connects to ground on uC
OUT – Connects to a digital interrupt input on uC