[SOLVED] [Help] RF Module 433MHz !!

[kunaltg]

I brought 433 Mhz RF transmitter + Receiver Module from Ebay :- **broken link removed**

These are intended to use with Encoder or uC or Arduino !!

But I want to use this module for simple implementation of single RF switch (Some what like Remote Controlled LED). But I dont want to use controller or any Encoder decoder for this as i want to keep it as small as possible !!

I tried this module for my purpose (connected LED in between Data & GND of reciver ,& started making DATA pin of Transmitter High) But it works in weird manner ,,Sometimes it works like charm but some times LED glows on and off on its own without any input !!

Is there any way with which i can implement a single switch action using this module without any additional IC !!

Here are some details of the module i got from google ! :-

http://www.romanblack.com/RF/cheapRFmodules.htm

**broken link removed**

 

[FvM]

This can't work due to operation principle of receivers. With no or unmodulated carrier present, the data output state is undefined and may also change. You need at least a simple modulation to get a defined receiver signal. To sort out all kinds of interferences that might mimic a modulated carrier, it's highly suggested to use an unique modulation patter, as all standard RC encoders do.

 

[kunaltg]

Ohhk Thnk you for your valuable reply !! ,,Do you know any other rf module smaller than this ?? Or any smaller circuit which i can implement for my purpose ?

And can i use HT12E & HT12D with this module ??

 

[kurapika312]

I have the same modules. Intrinsically the module outputs random pulse when there is no transmission.
If you want it to work as you plan, you should modify the circuit.
I don't remember the value well, but place your receiver horizontally on the table. Right over the Opamp (LM358) , there is a resistor and a capacitor in series. Short the capacitor and remove the resistor.
Also between the 2 inputs of the comparator(that is the 2nd opamp of the pair) there is a 200k resistor, maybe. Remove that resistor too.
The range is reduced (probably half as far as the original one) but there is no random pulse. Good luck !

By the way I did the same thing. It works at 15 meters (with antenna = 17 cm straight wire) and several glass pane door in between. In open space i tested it and found it ok at 50 meters. It's enough if your house is small.

 

[kunaltg]

thank you kurapika312
,,But can you tell how much range i can get with the modification ( I mean in meters like 20 or 25 meters ?) , it seems that we are tweaking with the gain of the receiver right ??

- - - Updated - - -

I have the same modules. Intrinsically the module outputs random pulse when there is no transmission.
If you want it to work as you plan, you should modify the circuit.
I don't remember the value well, but place your receiver horizontally on the table. Right over the Opamp (LM358) , there is a resistor and a capacitor in series. Short the capacitor and remove the resistor.
Also between the 2 inputs of the comparator(that is the 2nd opamp of the pair) there is a 200k resistor, maybe. Remove that resistor too.
The range is reduced (probably half as far as the original one) but there is no random pulse. Good luck !

By the way I did the same thing. It works at 15 meters (with antenna = 17 cm straight wire) and several glass pane door in between. In open space i tested it and found it ok at 50 meters. It's enough if your house is small.

Thanx A LOT !!!

 

[kurapika312]

Ah I forgot one thing. The receiver cannot output "1" for a long time, its output cannot hold. So if you might want to think twice about your project if you use it for remote switch

 

[kunaltg]

^ Yeah I know that ,,, it gives output in Pulses form ,,, but i don't worry about it as i want to connect a buzzer over there !! ,,But Thank you for your help !!