Correct wiring for 433MHz transmitter/receivers?

Question

I have ordered some of these commonly used 433MHz transmitter/receiver units with the intention of using my Pi GPIO pins to send and receive radio signals. I have my approach mostly figured out, but the one thing I can't get a clear answer on is how I should wire the units to the Pi's GPIO pins.

A lot of tutorials I come across (just do a google image search for 'Raspberry Pi 433MHz receiver' to see what I mean) tell me to wire the VCC, Data and GND pins on the transmitter and receiver directly to the 5V, GPIO and GND pins on the Pi respectively. This would be all right PROVIDED the receiver and transmitter Data pins don't send out voltages greater than 3v3 to the GPIO pins. However, I'm very sceptical about this direct wiring, especially as the units are being powered by 5V.

My question is this - has anyone got experience with these units and can tell me what sort of voltages the Data pins produce when the units are powered with 5V? Should I be wary of the tutorials which tell me to wire like this (which seems to be pretty much all of them)?

I know that this is a bigger deal with the receiver as the GPIO pin will be taking input from the Data pin to get the readings. It will be configured as as an output pin for the transmitter, but someone on another forum warned me that until the pin is actually configured as an output, it is still possible for excessive voltage to damage it. So before I actually continue with this project I'd like to get some insight as to how to wire and power both the transmitter and receiver.

Thanks a lot for your help!

Answer 1

You will to need to measure the voltage yourself.

No one can guarantee the modules you receive will be as illustrated or the same as theirs.

If you power the receiver from 5V or more it is safest to use a voltage divider between data out and the receive GPIO.

The transmitter side is irrelevant. The data in pin on the module is an input from the Pi, not an output. You can connect the transmitter data in pin to a GPIO regardless of whether you use 3V3 or 5V power.

Answer 2

I've used those modules. They work with 3.3 volts, but the transmit power would be better when using 5 volts.

Simply connect VCC to 3.3 volts then wire everything else exactly the same and you should be good to go.

For the transmitter, you can safely connect VCC to 5 volts since the data pin only receives data from the Pi.

Answer 3

Thanks for the answers, that's very helpful :) I only need to use the receiver to sniff the codes sent out by another device once, so hooking it directly to 3v3 for this should be fine provided it works. If it turns out that it only works with 5v then I'll make a potential divider like this:

Good to know about the transmitter too, as this is the important bit :)