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This circuit is designed to turn on/off any household or industrial appliance using a TV/DVD remote control. The circuit can be operated at a distance of 5 to 10 meters depending on the remote control used. The circuit includes a step-down transformer 'NE555 timer IC (IC2), IR. receiver module (IRX1 TSOP1738) and several separate components. The circuit operates on a regulated 5V power supply, originating from X1 and regulated by IC1. The home appliance is controlled by pressing any button on the remote control or by manually pressing switch S1 to put the appliance in the “on” state. The TV/DVD remote produces a frequency of 38 kHz.
The IR receiver module operates at this frequency. It is used to control relay RL2. Trigger relay IC2, wired in stable mode to control the household appliance connected to the contacts of relay RL1. Timer IC2 turns relay RL1 on and off when switch S1 is pressed momentarily. The threshold and trigger input pins 6 and 2 of IC2 are held at half the supply voltage (5 V) by resistors R2 and R3. When output pin 3 of IC2 is high, capacitor C4 charges through resistor R4 and discharges when output pin 3 is low. When switch S1 is turned off, the voltage from capacitor C4 is applied to pins 2 and 6 of IC2, causing the output of IC2 to change from low to high or high to low.
When switch S1 is released, capacitor C4 charges or discharges to its original level at output pin 3 of IC2. Under normal conditions, when the infrared rays do not reach the TSOP1738, its output on pin 3 remains high. When you press any button on the TV remote control, infrared rays hit the TSOP1738 and its output becomes weak. At the same time, relay RL2 is energized for a few seconds through pnp transistor T2 (BC558). The operation of the circuit is very simple. Initially, when no infrared rays fall on the infrared receiver module, its output remains high. Transistor T2 is in cut-off state. Relay RL2 is not powered and therefore IC2 does not switch.
Therefore, the household appliance connected to the contacts of relay RL1 remains off. When you press any button on the remote for the first time, the output of the IR receiver module will be low and the collector of transistor T2 will be high. Relay RL2 powers and activates IC2. The output of IC2 goes high and relay RL1 supplies power to turn on the device. When relay RL1 is energized, it remains in this state. Therefore, the device connected to the contacts of relay RL1 remains on. Now, when you press any button on the remote for the second time, relay RL2 will energize and reactivate IC2.
The output of IC2 becomes low and relay RL1 de-energizes to turn off the device. When relay RL1 is de-energized, it remains in this state. Therefore, household appliances remain turned off. This cycle repeats when a button on the TV remote control is pressed to turn the device on/off. Assemble the circuit on the general-purpose PCB and place it in the appropriate cabinet. Attach TSOP1738 and move S1 to the front of the cabinet. Place the transformer inside the cabinet and the AC power cord at the back of the cabinet.