Wireless RF motion Sensor using 434Mhz Tx Rx module

Hi everyone,
I'm a beginner in RF and would like to know about the use of 434Mhz Tx Rx ASK module without any encoder/decoder for sending a square wave tone signal
from a 555 timer circuit.
Let me explain in brief, I have a PIR motion sensor (HC SR501) and I want to develop a wireless alarm circuit that can send a Beep signal (from 555 multivibrator circuit) whenever motion is detected. When there is a motion the PIR output will be high, and it will turn on the beeper and transmitter by a NPN transistor. The Rx module is a superheterodyne reciever with 8 pins. I want the receiver circuit to be very small, so i dont want to use HT12E/D IC's. Can I connect a piezo buzzer directly to the Linear O/p pin of receiver to produce sound? Here I am enclosing some schematics, Please help me to get it work.

I tested the same circuit type and it worked. Make sure the 555 can trigger well (I used a comparator before it, to get a good trigger pulse), and the receiver outputs are two, one direct from detector, another TTL. Do not overload the outputs, use an amplifier if possible. I used a piezo buzzer which does not load the output.

I wired this circuit on a breadboard with Tx and Rx and with suitable wire antenna. But it is not giving any sound from receiver. I checked the transmitter circuit by replacing the Tx module with piezo buzzer, and it is working fine whenever there is a motion. How can i check whether the transmitter is sending data or not. I am using small buzzer found in the small quarts clocks. And I doubt about the receiver output to the buzzer, whether it can really run the peizo. Plz correct me if I am wrong

Aseef said:

I wired this circuit on a breadboard with Tx and Rx and with suitable wire antenna. But it is not giving any sound from receiver. I checked the transmitter circuit by replacing the Tx module with piezo buzzer, and it is working fine whenever there is a motion. How can i check whether the transmitter is sending data or not. I am using small buzzer found in the small quarts clocks. And I doubt about the receiver output to the buzzer, whether it can really run the pieizo. Plz correct me if I am wrong

Click to expand...

I used the schematic similar to yours, and it worked.I used the piezo element on receiver output.
The receiver is a super-regenerative type, and it needs to be tuned for the best response for the transmitter modulated by ~by 3 kHz.
I would recommend to test the setup with the transmitter modulated by the 555 running at 3 kHz, located several meters from the receiver. Tune the receiver coil for the best response, then increase the distance, and retune again.
I had no problem with the system, it operated well. I used a 555 as a free running audio oscillator at !~3 kHz which corresponds to the piezo element resonance.
To reliably trigger the 555 from the PIR sensor I used a LM310 comparator.

As antennas I used quarter-wave wires,and my system worked over ~ 30 meters. For a longer distance use better antennas, like yagis or corner-reflector dipoles.

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If in doubts with the receiver, try to insert an audio amplifier to "data output", with a speaker or headphones. Without the transmitter signal you should hear a loud noise. With the transmiter signal, the noise goes away and the modulation frequency appears in a full strength at receiver output.
The system is designed to function over a short distance with short antennas but it must be tuned for best results.
Be patient and increase the distance in steps. Good luck!