This page describes two Optical Flow Sensors produced by Pimoroni.


Normally the PMW3901 Optical Flow Sensor is used by flying drones to measure the distance moved over the ground. In the case of a Mecanum-wheeled robot, the PMW3901's camera would be mounted just over its 80mm minimum focal distance and its x,y output used for the robot's odometry, i.e., to measure how far the robot has traveled.

While the sensor itself provides numeric values, this video shows a test rig using a 5x5 RGB LED matrix that indicates which direction the sensor has moved by color: red for port movement, green for starboard, cyan for forward and yellow for aft.

There's a blog entry and YouTube video about the Pimoroni PMW3901 Optical Flow Sensor:


Prototype fabrication of the PAA5100JE (click to enlarge)

The PAA5100JE-Q is PixArt Imaging's latest optical navigation chip designed to enable navigation with working range of 15 mm to 35 mm over various surfaces. It is housed in a 28-pin land-grid-array (LGA) package that provides X-Y motion information. Aided by external illumination [two built-in LEDs on the Pimoroni board --ma], it is most suitable for motion and surface detection in robot application.

Key Features #

  • Working range of 15 to 35 mm
  • No lens focusing required during lens mounting process
  • Power consumption of 6 mA typical @ run mode (chip only)
  • 16-bits motion data registers
  • Motion detect pin output Internal oscillator – no clock input needed


  • Devices that require near field motion detection, e.g Robot Cleaners