IR Based Automatic Hand Sanitiser Dispenser

The IR Based Automatic Hand Sanitiser Dispenser operates as a touchless, automated fluid delivery system utilizing a discrete analog control circuit. At the heart of the detection stage is an IR sensor module built around an LM358 operational amplifier. This sensor continuously emits and monitors infrared light; when a user places their hand within the detection range, the reflected IR radiation alters the sensor's output state, generating a control signal. This low-power signal is routed to the base of a BC547 NPN bipolar junction transistor, which acts as an electronic switch. When the transistor's base receives sufficient voltage, it enters saturation, allowing current to flow from the 5V DC adapter through the coil of the 5V single-changeover relay. As the relay coil energizes, its mechanical switch changes state, completing the circuit for the mini submersible DC motor pump. The pump then activates, drawing liquid sanitizer from the attached plastic bottle and pushing it through the small plastic pipe to dispense a dose to the user's hands. To protect the discrete semiconductor components from voltage spikes generated by the inductive load of the relay coil, a 1N4007 flyback diode is placed in reverse bias across the relay terminals. Additionally, an LED indicator visually signals when the circuit is triggered. The entire system is assembled on a general-purpose PCB and powered reliably via the 5V DC adapter, providing a responsive and hygienic touch-free user experience without the need for microcontrollers or programmed software.