Handheld RFID proximity alarm

Proximity or range sensors are used in many installations requiring an action according to the distance (D) of an object.
They are also used in robotics to control the movement according to the environment, in motorized or domotic installations, the applications can be many and very different.
There are a variety of proximity sensors, including the most common are position switches, Capacitive sensors, inductive sensors, photoelectric sensors where an emitter (E) and a receiver (R), ultrasonic sensors and magnetic sensors are required.
Each of these sensors have the same function, but each of them uses different systems for the detection, either by contact, sound, etc.
Its detection capacity varies according to the type of sensor, and can vary from millimeters to meters. We can vEr these sensors in automatic floor cleaning systems, safety barriers, rear parking sensors for cars, mobile phones, etc.

Within the detection systems we can find different types according to their operation, among them the most common:

1. Infrared sensors
2. Vibration sensors.
3. Photoelectric sensors.
4. Ultrasound sensors.
5. Acoustic sensors

Each type of sensor uses different detection methods and each one is recommended according to the situation.

1. Sensors by infraRrojos, are one of the most used types, thanks to its reliable operation and installation, since we can find this type of wired and wireless sensors.
   The infrared sensor has a phototransistor capable of detecting the infrared electromagnetic radiation emitted by a body, this type of radiation is not visible by the human eye. A change of radiation in its perimeter will activate the relay and proceed to send ato alarm signal.
   Within these, there are two models, passive infrared sensor, which only has a phototransistor and assets, which have an emitter and a receiver.
2. Vibration sensors are used mostly in security systems, such as window sensors. car alarms etc.
   Its operation is based on an accelerometer, through a piezoelectric sensor. This type of sensorDue to its construction material it allows to detect changes and pressure when emitting an electric charge.
3. Photoelectric sensors, these are the sensors that use photoelectric rays, normally a transmitter and a receiver are used, they are commonly used in automatic door systems, elevator doors, production chains, etc.
4. The ultrasonic sensors are those that emit an acoustic signalabout 30 kHz, a signal that is not appreciated by humans. This signal or wave propagates through space, walls, objects, doors, etc. once the signal has spread the sensor is activated and any change will trigger the sensor.
   These types of sensors are also used in devices that require measuring distances and detecting objects.
5. Acoustic sensors, are those that can detect the signal emitted by anyobject and are able to detect the pressures that the acoustic waves emit, such as the noise of the crystals when breaking a window.