I couldn't find a single example about how to connect a regular PIR sensor of a security alarm system to my Arduino. The datasheet indicates:
Terminals:
| -12V+ | TAMP | C | NC | 3K9 |
| Power input: |
8.2-24vdc |
| Alarm output: |
N.C 50mA at 24vdc 10ohm in line resistor |
| Tamper Switch: |
N.C 50mA at 24vdc 10ohm in line resistor |
My guess is that I can connect an external power source to the PIR sensor, probably a 12VDC power supply, then I can run a wire from a digital PIN in my Arduino to the NC terminal in the PIR sensor.
Am I correct on this? Do I need a resistor on the Arduino digital pin?
Regards
When the outputs are NPN (open collector), you also need pullup resistors to the Arduino Vcc. 1k should work.
I'm not sure about the 10ohm in line resistors, they may be intended to detect attacks by shorting the lines to Gnd?
Thanks DrDiettrich,
Not sure if I understand what you just said.
Here is an image of what I have in mind. I added a 1k resistor.
The Arduino is going to be powered by the USB cable for now I guess.
I couldn't find a better PIR sensor so I am using the one that is designed for Arduino, but in this case, the PINS in the sensor are - / NC / +
I would get a multimeter and check the resistance between the C and NC. I expect that it will be 0 ohms when normal and open when active. If so, use it as a simple switch with a pull-up resistor.
Weedpharma
JonathanCR:
Here is an image of what I have in mind. I added a 1k resistor.
I couldn't find a better PIR sensor so I am using the one that is designed for Arduino, but in this case, the PINS in the sensor are - / NC / +
When NC means an Normally Closed contact (to Gnd), it can only pull the signal line low, not high. That's why you have to add an resistor from the line to Vcc, that keeps the line high when the contact is open.
