Grower is a small ‘rover’ vehicle which navigates around the periphery of a room. It hugs the room’s walls and responds to the carbon dioxide levels in the air by actually drawing varying heights of ‘grass’ on the walls in green ink. The Grower robot senses the carbon dioxide (CO2) level in the air via a small digital CO2 sensor. This sensor is mounted high on a wall of the exhibition space and sends data wirelessly to the robot. The number of people in an exhibit space breathing in oxygen and exhaling CO2 has an immediate effect on the sensor. My robot takes a reading of the CO2 level every few seconds and in response it draws a vertical line in green ink on the wall. Thanks Doug! Link.