This is an Infra-Red Sensors that we have improved through multiple designs. The circuit modulates the light at two frequencies, at 40 kHz pulsed at 20Hz. This double modulation makes the sensor even more immune to interference, and also has the effect of reducing the current consumption as the LED is only illuminated for a small part of the time. Two sensors can be incorporated on a small PCB using just one integrated circuit. Due to the length issue of the circuit board, we have added an additional board to make the circuit appear less crowded. In addition, we have also redesigned the circuit so that the LEDs are all on the same board for easy observation.