500 metre radio data link

Posted on Feb 4, 2014

Have a water tank you want to measure or a dam or a gate Want to detect a car coming down the drive but don`t want to string wires through the garden This instructable shows how to send data 500 metres with 100% reliability using picaxe microcontroller chips and 315Mhz or 433Mhz radio modules. The transmitter and receiver circuits are quite simple and use picaxe chips. These single chip

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microcontrollers can sense analog voltages, turn things on and off and can transmit data. See instructables and for a description of how to program picaxe chips. With a radio link as well as an interface to a PC it is possible to sense data remotely and transmit it anywhere in the world. The transmitter prototype was built on a piece of prototype board. There are a myriad of low power 10mW RF modules available which work well up to a range of about 30 metres. However, once the power goes up above half a watt the RF tends to get back into the picaxe chip and cause resets and other strange behaviour. The answer is to remove the module`s antenna and take the RF away with 3 metres or more of 50ohm coax and build a proper dipole antenna. This also boosts the range considerably. I`m trying to use a number of xtmr`s with PICAXE chips providing unique IDs to a single RCVR PICAXE combination. All I need is one XTMR on at a time. Once the ID has been received, the receiver needs to listen for another XTMR`s unique ID Good question! I think the newer picaxes get around a serial hang, but the older ones are already hanging when a serin instruction is run. So it is stuck and won`t go any further until it gets the header. There will be noise but it doesn`t matter so much as the pic doesn`t have any other tasks to do until a packet is received. I did find this a bit of a limitation though, and have moved a lot of my projects over to the...

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