Any "button" of any remote control may be used to work this universal switch. The button must be pressed for about one and a half seconds (determined by R3 and C2) before the relay will operate. The circuit will remain in this state (latched) until reset. To reset, any button is pressed on the remote handset and held for a short duration.
For example, if you were watching TV, you could press and hold any button on the TV remote to trigger the circuit. In order not to change channel, you could press the button of the channel you are watching. You can connect anything to the relay, for example a lamp, but make sure that the relay contacts can handle the rated voltage and current.
Circuit Operation:
IC1 is an Infra Red module. IR modulated pulses are received and buffered by this IC. It has a standard TTL output, the output with no signal is held high by R1. One gate of a CMOS inverter drives LED1 as a visible switching aid. Another gate buffers the signal and applies it to the time constant circuit, comprising R3,C2,R4 and D1. C2 charges via R3, and discharges via R4, D1 prevents quick discharge via the low output impedance of the CMOS buffer. The time taken to charge a capacitor is the product of resistance and capacitance, more commonly known as the RC time constant. At one RC a capacitor will only charge to 63% of the supply voltage. It takes 5 RC's for a capacitor to reach 99% charge. In this circuit the capacitor charge has to reach the logic threshold of the CMOS invertor. As the power supply is 5 Volts, the input threshold is around 3.6V, which takes about 3RC's or about 1.5 seconds. Once reached the inventor triggers the 555 timer and operates the flip flop
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