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

500 metre radio data link
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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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