Just move hand in front of this Liquid soap dispenser. You get few drops of liquid soap for hand wash. Made it Non contact to prevent hand contamination from the press handle of the dispenser if it is used in common places.

 

 

 

The circuit has a Proximity sensor using Infrared LED as emitter and Photodiode as receiver. The Photodiode is connected to the Inverting input of the Op Amp LM358 which is designed as a Voltage comparator. So normally, the output of the comparator will be low as adjusted by the preset. When the hand is moved in front of the Proximity sensor, reflected Infrared rays from the IR LED falls on the Photodiode. This change the output of IC LM358  high and triggers the Medium power NPN transistor BD139 to drive the Solenoid DC pump. It then pumps few drops of liquid soap through its outlet. When the hand is withdrawn from the front of Proximity sensor, soap dispensing stops.

Make a leak proof container to fill the liquid soap. Connect the inlet and outlet of the pump to plastic tubes. Tube in the inlet should be immersed in the liquid soap and fix the tube from the outlet to the outside. Enclose the circuit in a case and fix it on the top of the container filled with liquid soap.

Components

This can be used as Automatic Sanitiser dispenser also. But the container to fill the sanitiser must be air tight to prevent the evaporation of sanitiser since it is alcohol based.