Today, electronic power sensors are present in a multitude of devices that surround us. There are several types of electronic presence detectors. Surely you think of those that activate an automatic door when you approach, those used in alarms to prevent intrusions or those that turn on a light automatically. But… How do I know which one I need? Today we want to talk about it.
They have become something very necessary and so normal in everyday life that they usually go unnoticed but are missed when they fail. However, we know little about how they work and what the different types are.
In general terms, the most popular presence detectors are usually PIR-type sensors, also known as Infrared sensors. PIR sensors work through heat detection. These sensors measure the ambient temperature of a room using sensing beams.
Its main advantage is that when one of the beams detects a difference in temperature, the sensor is activated and the lights in the room come on. When the beams detect that the room has returned to its original temperature, the lights turn off.
What are the disadvantages?
Most PIR sensors are sensitive to high or low temperatures, this means that their performance may be affected. Also, since PIR sensors are not sensitive to motion, they do not offer the same coverage as other types of sensors. A PIR sensor might take a little longer to detect and activate a floodlight when your dog goes out into the garden or a car pulls up in front of your house. This is due to the way the PIR sensors are activated.
These sensors may not have the aesthetics that some consumers seek. They cannot be hidden inside the luminaires and must be installed outside of the luminaires or on an external surface. This means that the sensor is usually placed in front of the luminaire, which can affect the aesthetics of the room.
Another type of sensor that is having great acceptance are microwave sensors, let’s see how they work.
A microwave motion detector is a device that uses Doppler radar to detect and measure the movement of an object. For most people, the two most familiar forms of this mechanism are used in a home security system and in traffic law enforcement.
The microwave motion detector is typically a single unit device that emits a pulse of microwave energy and then detects its reflection. Thanks to the Doppler effect, it calculates the time required for the reflection and the change in frequency, so is able to determine the distance, direction and speed of the object being observed.
Furthermore, these types of sensors are capable of detecting movement behind non-metallic objects. However, they also have some drawbacks.
What are the disadvantages?
Microwave sensors have a high level of sensitivity and if they are installed or configured incorrectly they could be activated by mistake as in cases of heavy rain or in which the wind causes movement in nearby trees, although this happens in very rare occasions. While this can occur when using cheap microwave sensors, most of those manufactured today have adjustable settings that allow the end user/installer to modify the detection zone and its sensitivity, helping to reduce the frequency from mistaken light activations.
So, what type of sensor should you choose?
The answer to this question depends on the application and the level of sensitivity required. If you want to install lighting sensors in residential applications, the PIR sensor is the most suitable for your needs. On the other hand, if you want lighting with a higher sensitivity, the microwave sensor is the ideal solution.
At Ingeniería Electrónica a Tu Medida we have experience in carrying out electronic designs based on one or another sensor and if the application requires high reliability, we combine both, achieving very high detection levels.
We have used them in UV-C and Ozone light generators that make sure that no one is present before acting.
Also in security systems that detect human presence even if it remains immobile for a long period.
Now that you know all this, which one would you choose?