I've just bought a 433Mhz digital transmitter/receiver set and tried to wire them up using the pi. Unfortunately my electronic skills are very basic and now my receiver gives me a "pulsing" signal (like every 500ms a LED is shortly switched on). Here you can see my current setting:

my current setting

At the top you can see the three pins of the receiver module. GROUND, DATA and, VDC. I connected VDC and GROUND directly to the corresponding pins on the pi. For the DATA pin it is written in the manual, that you can get the transmitted signal from GROUND and DATA. So, I am not sure if my setting is correct. The pulldown is for the GPIO pin so that it's state can be clearly identified (I hope that I understood that right). Is that a wrong resistor? On my recv module there is a ic with the printing "2904D JRC D142A". Maybe that helps identifying the problem?

As far as I know, there is no timer, I have to transmit the signal myself e.g. by using the Manchester Code.

Aside from that, when moving the recv module the LED is blinking weirdly, too. Do you know why?

EDIT: And when sending a 1, the LED goes on for like 500ms and then slowly turns off. Why is that? :)

1 Answer 1


On the transmitter side power from 5V and ground. Connect a gpio to the OUT pin.

On the receiver side power from 3V3 and ground. Connect a gpio directly to the IN pin.

Your module may have different names for the TX OUT pin and the RX IN pin.

Don't use a pull-up or pull-down on the IN or OUT gpios.

If you want to power the receiver from 5V then you will need to use a voltage divider on the IN pin to drop the voltage to a Pi safe 3V3.

As to the LED the RX side will be receiving static when the transmitter isn't on and its AGC will be all over the place. Once the transmitter starts the AGC will cut out most of the noise.

  • Sorry, for does AGC stand for? Feb 21, 2015 at 15:49
  • "> when the transmitter isn't on " but it is on... Feb 21, 2015 at 15:50
  • When it isn't transmitting.
    – joan
    Feb 21, 2015 at 15:56
  • Okay, awesome. It seems like it's working. Could you please explain, 1) why I need 5V? 2) why I don't need a pull-down resistor (does the LED count as one here?)? 3) What AGC does stand for? :) Anyway, thank you very much! Feb 21, 2015 at 16:00
  • Generally the higher the voltage the better the transmit range. Not sure if it matters on the receive side. However the 3V3 supply on the Pi is limited. Check the module specs for the permitted voltages. You don't need pull-ups/downs if the line is permanently driven high or low (as it is by the OUT pin of the receiver when powered). AGC, Google? Automatic Gain Control.
    – joan
    Feb 21, 2015 at 16:15

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