Infrared encoder emitter seen through LEGO wheel Humans cannot see infrared light however, the digital camera detects and displays it as faint purple. The photograph below has the detector removed so that you can see the infrared light from the detector’s perspective.

The greater the amount of light, the higher the voltage present between the two components (where the purple sensor wire attaches). The detector is in series with a 22 kilohm resistor to divide the battery’s voltage between the resistor and the detector. The 180 ohm resistor prevents too much current from passing through the emitter, which would damage it.Īt a maximum of 5 volts (when plugged into the STK500 programming board), the emitter will receive about 18 mA.Ī lower resistance would produce a brighter light, which might be so bright as to pass through the plastic Lego wheel or bleed around the corners to provide an undesirable constant detection.Ī higher resistance might not produce a bright enough light, particularly when the battery voltage is just above 3 V. Underneath the board is an infrared emitter (LED) and an infrared detector (photosensor) arranged as an interrupter pair.īreadboard with pushbutton on the front and infrared emitter-detector on the back

In the rear, towards the bottom of the robot, is a breadboard with a large pushbutton. Instead, that wheel rolls freely to detect the distance traveled. The third wheel is not connected to a motor. As we’ve seen, Afterthought Cake is a tripod robot.

Encoder wheel robot 20 slot