Making PIR sensors wireless?

Hello. I was wondering if there is a way to send data wirelesly from sensors (like PIR motion sensors) to an arduino board without using two arduino boards.

I assumed that it would work to connect a PIR sensor to a "RF Link Transmitter" but someone said it needs code on the transmitter end too. So is is some kind of component/controller that can make the PIR sensor send data to the RF transmitter?

The idea would be to have one ardiuino board in the house and 2-3 wireless pir sensors around the house for an alarm :)

Or maybe there are some cheaper smaller Arduinos so I use them on each sensor?

The XBees can collect digital sensor data and transmit it, without the need for a microcontroller.

Create several XBee + PIR sensor + battery setups, and have each of them broadcast to one XBee connected to an Arduino.

Not terribly cheap, though. And, don't forget that the PIR sensors generally need 12V to function, and the XBee needs 3.3V.

I did find a 3.6V PIR sensor:

  • That mentions some processing capabilities, can't it be linked to RF transmitter directly?
  • I will look into xBee and above sensor but I think xbee modules are expensive in general, I mean more expensive than simple RF transmitters.

That sensor is interesting. It includes a microcontroller that outputs serial data. Exactly what these need as input. Only problem is this note: Only one 315MHz transmitter will work within the same location.

Do you think it would work to have two different transmitters (434MHz and 315MHz) and again two receivers on the Arduino? So that I can receive signal from both PIR sensors.
I am a beginner with Arduino (UNO), I assume this would work and it has enough pins to put two receivers on it?
Thanks for the tips.
If not then I will probably use one pir sensor with wires (closer to Arduino) and just one wireless.

Edit: if that works right then it would be around 20-25$ / for one sensor with transmitter/receiver included which is nice I think.

Having two different frequencies should work. One will need to be connected to pins 0 and 1. The other will need to be connected to two other digital pins, and NewSortSerial used to read that one. Two is the limit though, as only one instance of NewSoftSerial can be active at a time.

You can get these for $8 or less on ebay . . . They will transmit to a single 315kHz receiver (detuned to 310kHz) that is interfaced to an Arduino. Each transmitter can be set to have it's own address so you can tell them apart. See this post on my blog that shows how to do this. Caveats: - The PIR sensors only transmit. - The range is good inside the house - outside is iffy unless you use a good antenna on the receiver. - 315kHz might be an issue in some countries. BTW, You don't need to control the transmitters and receivers through the UART (Rx/Tx) no matter which way you go. You can use any pin. Check out the VirtualWire lib.

An alternative, low-tech approach: get some cheap car-alarm type remote control transmitter / receiver pairs, and pull the case off the transmitters. Mount it inside the PIR case with the "normally open" outputs wired across the transmit button.

Then the Arduino can be connected to the receiver to detect when a signal has been sent.

Jon Freetronics:

Thanks for the replies. At this point I have ordered 2 PIR sensors from SparkFun and two RF transmitter/receivers (different frequencies), they are not expensive and I can still use them for other things in case this would not work right.

I also looked that the above sensor (in image), they are cheap, around 6.5$ on ebay with free shipping (sensor with transmitter in it). And there is also a kit with with wireless sensor and main alarm in the house, similar to what I am trying to do and the complete kit is ~24$ on eBay :-?

About the car tx/rx, on first look I only found some around 30$, I might look more into that if the radio thing would not work.

Next I need to find an IR keyfob with 2-3 buttons to stop/start the alarm from distance. Anyone knows something like that? I know about a keyfob with some radio in it but IR would be enough for this.