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  • Electronic Soap Dispenser

  • Created: May 17, 2016

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A soap dispenser is a device that is often found in a restroom. It is a device that if pressed or triggered, releases soap for handwashing. There are different designs of soap dispensers. The design of a manual soap dispenser depends on what form of soap it contains. In this reference design, the soap dispenser is designed as electronic or automatic type.

The electronic soap dispenser in this design utilizes an infrared proximity sensor (LED1 & PD1) to detect a hand. The 10kΩ potentiometer (POT1) is used to adjust the proximity detection sensitivity of the whole circuit so that if a hand is detected by the sensor, the voltage at the non-inverting terminal of the MCP6001UT-I/OT is greater than the voltage across the inverting terminal. When a hand is placed under the IR sensor, the MCP6001UT-I/OT op amp that acts as a comparator outputs a signal that drives the NPN transistor (Q1). This transistor drives the solenoid that is used to release the soap from the dispenser.

In creating the electronic soap dispenser hardware, the mechanical layout should be carefully observed in order for everything to fit perfectly. It is also recommended to build the circuit in a modular design. The infrared emitter (LED1) and the receiver (PD1) should be placed at the front side. The IR emitter and receiver should be at least 10mm apart, and face downward. All interconnecting wires should be secured with cable-ties.