PIR sensors suitable for 24VDC
Quite often I have been asked for any recommendations for motion sensors that could be used in SmartHome installations. Obviously, there is a wide range of products on the market these days, however there are two important attributes people mostly care about.
Motion sensor must be totally silent
I am sure no one would love to hear the annoying clicking sound of the relay inside the device every time sensor registers movement. Several users did DYI hacking to bypass the relay so make sure you don’t go down that avenue. Most of the cheap PIR sensors sold in Hobby Markets do have noisy relay inside as these are originally used for 230 Volt direct light/load control and thus are not suitable to act as digital sensors for SmartHomes. Look for sensors that are designed for Alarm systems instead.
The design of the unit being acceptable for home use
This is highly preferential thing, but you’ll probably agree that these sensors should not cause interior look degradation when mounted in your house or apartment.
I do have very good experience with Satel PIR sensors, namely Aqua S (wall mount), and Aqua Ring S (ceiling mount). Both are capable of working on 24V DC and are reliable products as far I can tell. These are pretty nice looking, with the expected features (like sensitivity setting in three levels, LED on/off). The manufacturer declares its consumption around 9,5mA at 24V and highlights its digital temperature compensation, high sensitivity, low noise level and high resistance to electromagnetic interference.
I also have installed the original Loxone PIR sensor from Esylux. The advantage of this one is the analogue output giving you the intensity of illumination in the given space, but is a bit bulky device and significantly more expensive. Moreover, the Easylux PIR (sold as presence sensor by Loxone) has a lot of internal features that are useful when used as a standalone PIR for light control. Using it just for motion detection is kind of hardcore I think.