In everyday life, the proximity sensor is used almost everywhere. On cars, it helps with parking, on conveyors it tracks the movement of products, in modern phones it blocks the keyboard after applying the device to your ear. In everyday life, this miracle of technology also found its place. Such devices are installed instead of a switch, for example, on the street. As soon as you approach the house, the light automatically turns on, and after a while it turns off. In security systems, it is generally impossible to do without sensors.
Distinguish proximity sensors by type: capacitive, inductive, optical, ultrasonic, microwave, magnetically sensitive, pyrometric, etc. Which type a particular device belongs to depends on how it works.
The capacitive proximity sensor is mainly used in security systems, because it detects the approach of an object and cannot miss it in any way. This distinguishes it from ultrasonic or infrared counterparts, the sensing distancewhich strongly depends on the surface of the object. For example, an infrared proximity sensor responds to thermal - infrared - rays. Ultrasonic devices first emit and then receive beams reflected from the surface. According to the principle of operation, this proximity sensor is very similar to the locator. And everything seems to be not bad, the signal is reflected well from hard surfaces, but not very well from soft ones. And the intruder can bypass it, just by putting on something soft. It is for these reasons that it is best to use capacitive sensors, especially in alarm devices, to protect important and large objects. In this case, the antennas in the form of wires are horizontally attached to the fence and connected to the main device through a small capacitor.
Capacitive sensors also come in several types:
1. capacitor sensors. It is the circuits of the latter that are the sensitive part of this device. This type is used where noise immunity and high sensitivity are not needed, for example, in signaling devices that touch metal objects.
2. Capacitive sensors using a frequency setting circuit. This type of device is less susceptible to radio interference and interference than devices with capacitors. This type can be used in everyday life to turn on the lights, etc.
3. Differential-capacitive sensors. They differ from the above in that they have two antennas, not one, which provides suppression of the effects of the weather (rain, snow, thunderstorms, frost, etc.). Their scope is notdifferent from the sensors on the LC circuit. The only difference is that another antenna needs to be installed.
4. Resonance-capacitive sensors. The trip signal occurs in the input circuit, which is in a partially unbalanced state with respect to the signal of the high-frequency generator. The circuit is connected to it using a small capacitor (an element necessary for resistance in the circuit). Such sensors can be used both in field, rural and urban environments, but not very close to powerful sources of radio signals.
