Set up your washbasin tap so that it turns on when your hands are just below the water outlet. This automatic washbasin tap controller is based on infrared technology. When your hands or a tool block the IR rays, water starts coming out of the tap automatically. Automatic washbasin tap controller circuit The circuit is made up of 555 timers and has sections that send and receive signals. Both the sender and the receiver are powered by 5V DC. The transmitter always sends out IR rays, which fall on the receiver. When something gets in the way of the IR rays between the receiver and the transmitter, the output of the IR sensor briefly drops. This sets off a timer circuit in the receiver, which let’s water out of the tap for eleven seconds. The transmitter is built around the timer IC 555, which is used as an astable multivibrator to make a 38 kHz frequency (see Fig. 1).

Fig. 1: Automatic Washbasin Tap Controller: Transmitter circuit The output of the timer is sent to the transistor T1, which turns on the IR LED (LED1). Keep in mind that IR LED1 must be aimed at the IR sensor module of the receiver circuit. Its transmission wavelength is between 900 and 1100 nm, which is in the range where the TSOP1738 receiver module works best. The sensor module, monostable timer, and relay driver circuit are all parts of the receiver circuit (see Fig. 2). The TSOP1738 sensor module can pick up IR radiation that is changed at 38 kHz. When any IR radiation is detected or stopped, its normally high output drops for a short time. Circuit operation When IR rays don't reach the receiver, the sensor output goes low for a short time, which turns on timer IC2. For eleven seconds, the timer's output is high, and the relay turns the solenoid. During this time, when the

solenoid is turned on, it lifts the valve in the pipe, which lets water out of the tap. Solenoid valves are used for this specific job. The relay driver circuit is made up of diode D1, resistor R8, and transistor BC548 (T2). When the relay is turned off, the back emf creates high voltages that could damage the relay. This is where diode D1 comes in. Here's how you can figure out how long the timer will be on high: Ton=1.1 R6C5=1.1×100×103×100×10–6=11 seconds Fig. 2: Automatic Washbasin Tap Controller: Receiver circuit

When you put the IR LED and the IR sensor on opposite sides of the sink, use shielded wires or leads to connect them. Set up the IR LED and IR sensor about half a meter apart so that the IR LED's IR rays hit the IR sensor directly. Now, turn on the circuit's power source. When you put your hand between the IR LED and IR sensor, the relay turns on, which makes the solenoid open the valve so water can flow out of the tap.