Switch Sensor - Operating Conception

Switch Sensor - Operating Conception . A switch sensor is a semiconductor device that controls an external electric circuit using an integrated switch depending on the position of a remote observed object. In most cases household switch sensors observe human hands. The peculiar feature offered by a switch sensor is that you don't have to apply any mechanical efforts. They only thing you have to do is to slightly touch a special contact plate i.e. a sensor. The switch sensor has three main components: a sensor, an analysis and control semiconductor circuit and a power switch. When an object approaches the sensor's control area, it generates a specific signal which is converted into an electric signal powerful enough to actuate the switch. The switch bridges or breaks the AC or DC circuit. Let's have a look how the sensor switch works on the example of a simple circuit. The basic component is an emitter follower based on two transistors. An electromagnetic relay is connected to the emitter of the second transmitter. When you touch a sensor, AC voltage induced in a human body by a room electric wiring goes through the capacitor to the tandem transistor's base. It opens and actuates the relay which in its turn switches the required load. You see the diode is used to protect from voltage surges and the capacitor smoothes pulses. Any low-power relay with the supply voltage corresponding to the circuit power supply will work. The sensor switch operates at 9 Volts; the absorbed current at the load operating time is 20 milli amperes.

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