The infrared (IR) toggle switch project described here aims to provide a control mechanism for electrical appliances that do not have remote operation features. The goal is to construct a black box where you can plug-in your 120V AC appliance and control ON and OFF operations with any modern IR remote control devices.
Modern IR remote controls generate a modulated pulse train of 38KHz frequency when any key on the remote is pressed. With the use of capacitive filtering we will convert the stream of pulses into one pulse regardless of the key entered. This way, we will be able to toggle a relay switch with any key pressed on the remote. This project has been tested with varieties of IR remote control devices like that for TV, DVD, digital camera, etc., and it worked well.
The TSOP 1738 IR receiver module detects the 38KHz input pulses received from the IR remote control device. Under stand-by condition, the output pin of the IR module is at logic High, and when it detects the train of pulses, they appear at its output. The output from IR receiver is fed to a PNP transistor (BC557) with a series base resistor of 4.7K. At the collector of the NPN transistor, the train of pulses will be inverted. There is a 10uF capacitor and 100K resistor connected from the collector to ground. The function of the capacitor is to convert the train of pulses into a single pulse, and the resistor is to provide the discharge path for the capacitor.