萝莉影视

Infrared SensorsDesign Tools

Key points during design, prototyping, and evaluation

Relationship between the sensor type, install location, and electrode configuration

The types of pyroelectric infrared sensors offered by 萝莉影视 largely fall into the following two types, and the sensor electrodes have polarity.
Because the suitable sensor differs depending on the install location of the set, it is necessary to select the sensor according to the install location.

Types of sensors Suitable set installation location Electrode configuration
Dual type For human body detection in a wall-mounted set Two electrodes with the positive side and negative side in a side-by-side configuration
Quad type For human body detection in a ceiling-mounted set Four electrodes with the positive side and negative side in a crisscross configuration
Electrode configuration illustration

Electrode configuration

The sensor electrodes must be configured according to the install location.

Dual type

Dual type sensors have two electrodes. The electrodes with their own polarity on the positive side and negative side form one pair and produce one output.
Because it is sensitive to input which sequentially crosses (horizontal) the two electrodes, this type is suited to use in wall-mounted sets (human body detection from movement in the horizontal direction).

○ Configure the electrodes in the horizontal direction

Illustration of the signal output with respect to the dual type detection area

Dual type sensors are good at detecting motion in the horizontal direction with respect to the detection area.

× Configure the electrodes in the vertical direction

Illustration of the signal output with respect to the dual type detection area

Quad type

Quad type sensors have four electrodes. Using a structure that places two dual type pairs into one package, it combines and extracts the outputs into a single output.
Because the polarities are configured in a crisscross form, the quad type sensors are also sensitive in the vertical direction in contrast to the dual type sensors. Therefore, they are suitable for use in ceiling-mounted sets that place the detection area below the sensor.

Illustration of the signal output with respect to the quad type detection area

Quad type sensors are good at detecting movement from various directions with respect to the detection area.
Compared to the dual type, more detection areas can be set, allowing for slight movements to be detected more easily.
*Achieved by combining sensors with optical design.
However, caution is required when configuring the sensors if the direction of movement is fixed.

Output signal with respect to the detection area size

The output signal changes according to the distance.

Optical systems including Fresnel lenses must be set according to the detection distance and area where you wish to detect a human body.

Dual type

Image 1 of Dual type
Image 2 of Dual type. Need to adjust the amplification circuit  (Frequency response and gain).

Choosing a lens

Choose a Fresnel lens according to the number of detection areas that you wish to set. You can create a detection area based on the number of electrodes and the number of lens segments.

When a lens is not used

The image below shows the detection area when a Fresnel lens or other optical system is not used in front of the sensor, and the output signal is canceled out in the region where the red and blue circles overlap. In addition, the lens plays the roles of (1) focusing the infrared rays and (2) forming the detection area. Please evaluate infrared sensors together with a lens to achieve stable detection as well.

  • *Please refrain from using or evaluating sensors on their own.
Figure of When a lens is not used