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I am doing a simple project where I place sensors at different parts of the house and send data to my rpi. I am using the rf433 for the wireless transmission but I discovered I cannot do multiple transmitters to 1 receiver nor can have multiple sets of RF near each other or else it cannot send signal.

I don't want to use XBEE because it's too expensive. Any suggestions on how to solve this problem?

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You didn't provide any links to the modules or specifications.

The normal, no collision, method would be to poll each outstation: the controller sends out a request for data to each substation in turn and waits for a response. Some form of addressing is required. Assuming your radios can't do that you have a few choices.

  • Transmit continuously on different channels and have the receiver cycle through all the channels to capture the data. Since the channel switching will be out of synch with the data transmission you will have to wait for an identifiable "start of message" before reading and processing the message. Then switch to the next channel.
  • Transmit at random time intervals on the same channel. in this scheme each transmitter is woken up from sleep to transmit on the same channel. After transmission it goes back to sleep. if transmission times are short relative to the interval between transmissions and if the number of transmitters is not to great this could work without too many missed transmissions due to collisions.

In either case some form of error checking (by message checksum) should be used.

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The RF433 is a very simple module, and doesn't have any onboard support for handling protocols. You can have multiple transmitters and receivers - but you need to write software to handle the contention.

Fortunately this problem has already been solved multiple times - and this question has also been asked before.

Have a look at this answer : How to connect 20 wireless sensors in one receiver with arduino?

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