Here is a very simple infrared detector circuit which can be used to detect infrared light. The circuit is consist of only three components a RS-276-145 photo transistor, 330 Ohms resistor and a general purpose LED (Light Emitting Diode). When the photo transistor will receive any IR on its surface it will
make the LED glow. The circuit can be powered with a 9 volt battery, and can be fitted upper side of the battery.