433 MHz RF Receiver Signal Bounce

Hi All,

I have build a rf tx/rx circuit with cheap 433Mhz rf tx/rx modules available in the market and I get a strange issue with the receiver when it receives a rf signal. When I pressed a button on the transmitter I can see the LED on the VT (Valid Transmission) goes high and after about second later it goes high again even without pressing any buttons on the transmitter.

In order to prevent this I have introduced a delay in my uC about few seconds and I still want to find out what is going on.

Receiver has PT2272 M4 Decoder IC and the output from that IC is fed in to a PIC16F84A uC. Any thoughts on this.

Thanks.

I do not know the TX/RX you use, but the problem may be caused by a common DC power line shared with your uP. Try to insert a 10-Ohm resistor from battery to RX DC line, and add a 100 uF capacitor. Pulsed DC current of the uP may affect the sensitive RX. Take care also to use a metal box for the RX as the uP may also radiate some RF interference.
RX antenna should be located as far away from the uP and possible peripheral devices.

Thanks jiripolivka, I'll try that and let you know if that solves my problem.

Hi Jiripolvka, I have tried what you have suggested but I had no success. I also tried shielding the rx module with bit of Aluminium foil but that also seems unsuccessful. any other suggestions?

As I wrote, I do not know the TX/RX you use. The TX may transmit a pulse twice, or the RX may "bounce" if the TX is too close. If it is not too expensive, try another TX/RX pair.

I used such small 432 TX/RX pair for an indoor data link starting to ring a bell from a remote home entrance. I had no problem except poor propagation conditions, but I never had twice response.

If you disconnect the uP and use only LED indicator at RX output, is the response the same?

Review your PT2262 side, it may transmit although you do not press the buttons? Modify your transmitter side(PT2262) so that it is powered(VCC) only when a button is pressed. You can realize it using a few diodes... there should be a suggestion in the datasheet.