Proximity Sensor using HO 4R Sensor. Sensor Circuit 8

You can make a Proximity Sensor using the Infrared Dual Reflective Sensor Module HO 4R. It is a package containing an Infrared LED and a Phototransistor arranged side by side with an opaque partition in between them. In front of the module, there are two small openings, one for emitting IR rays and another for receiving the reflected IR rays. When there is an object in front of the module, IR rays reflects from the object and triggers the Phototransistor and the connected circuit will be activated. Range of the circuit is few centimeters.

When the circuit is switched on, IR LED in the module starts emitting IR Rays. If there is an object in front of the module, IR rays hit on it and reflects. These reflected rays enter into the module through the opening in front of the Phototransistor and triggers. When the Phototransistor conducts, its collector voltage drops and triggers the monostable using the IC555. LED will light for 1 minute.