PIR Motion Detector

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This page explains how different types of motion sensors can be connected. The same principles applies when connecting other type of equipment (like alarm systems and others) to an Openmotics Input Module.

Type of Motion Detectors

Different type of motion detectors can be connected on the input module. You can define 4 types of motion detectors:

  • DC powered Motion detector with relay contact
  • DC powered Motion detector with digital output (can be open-collector)
  • AC powered Motion detector with AC output
  • AC powered Motion detector with relay contact

We strongly advise to use only DC powered Motion detectors. AC powered motion detectors could be used but a relay is necessary to create a galvanic separation between the Motion sensor and the Openmotics Input module.

Voltage of Motion Detector

Depending on the motion detector, a DC voltage (since we concentrate on DC powered motion detectors) must be applied.

  • If you use a 12VDC motion detector, you can use the 12VDC power supply of your Openmotics system or you can use a separate DC power supply (don't forget to interconnect the GND output of this power supply to the GND output of the Openmotics Power supply)
  • If you use a 24VDC motion detector, the simplest thing you can do is to buy a separate 24VDC Power supply for the sensors. The GND (or "-") of the DC output of this 24VDC power supply must be connected to the GND (or "-") of the 12VDC Openmotics Power Supply.
  • If you use a 5VDC motion detector, you've 2 possibilities:
    • Buy a separate 5VDC Power supply for the sensors. The GND (or "-") of the DC output of this 5VDC power supply must be connected to the GND (or "-") of the 12VDC Openmotics Power Supply output.
    • Use a voltage regulator. Example is the 7805 (or TPS62175) which is very simple to use.

7805.jpg

Note: The 7805 is ideal for low power applications. If you apply many 5VDC sensors, the 7805 may heat up (thus a heat sink must be added) due to it's low efficiency. You have 7805 alternatives which have a switched design (with the same footprint like the TPS62175) but with an efficiency of 90%+. When many sensors are used, best solution is to use a separate 5VDC Power supply.

Output of the Motion detector

You can have different types of output a motion sensor can have:

  • Relay output
  • Digital output
  • Open collector output

Relay Output

When applying a sensor with a relay contact, it’s fairly simple to connect. In the below example, we use a 12VDC motion sensor with a relay contact.


PIR sensor with relay.jpg

Note: In the above example, we've connected 4 motions sensors. Of course, you can use all 8 inputs for motion detectors if needed.

Open Collector output

An Open Collector output does something very simple: It will bring the sensor output to the GND when the sensor triggers. Since Openmotics uses inputs that are pulled-up, sensors with open collector output can be directly connected like illustrated in the below example. In this example, we've used 5VDC powered motion sensors.


PIR sensor without ULN.jpg

Note: In the above example, we've connected 4 motions sensors. Of course, you can use all 8 inputs for motion detectors if needed.

Digital Output

The inputs of the Openmotics input module are pulled-up to 5VDC. If the sensor has a different output voltage, an ULN2803 has to be applied. An ULN2803 will convert the sensor output to an Open Collector Output. In the below example, we’ve applied 5VDC sensors with 3.3VDC output.

Note: Some sensors support the fact that 5VDC is applied as pull-up on the output of the sensor. In this case, the Open Collector schematic can be used.


PIR sensor.jpg

Note: In the above example, we've connected 4 motions sensors. Of course, you can use all 8 inputs for motion detectors if needed.

NO/NC

Some sensors will trigger the output when they see motion (NO – Normally Open), some will just stop when they see motion (NC – Normally Close). You have sensors that can be configured for NO/NC. Just note that both types (NO/NC) can be connected to the Openmotics system and are supported.

For more information, please see http://wiki.openmotics.com/index.php/CLI_Reference_Guide#input_invert_read_.5Binput.5D