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My home automation network has grown to 44 devices comprising both manual and timed transmissions which may be single-character or multi-byte messages. All contain micro-controllers. They form a mesh with various interoperability regimes. Transmissions are asynchronous at 2400 baud and last less than 100 milliseconds. The protocol used totally prevents false activation, but there are missed messges, They all use the same $5 Radiotronics transmit and receive modules.The RF components use AMK (ON-OFF) keying in the 433.92 MHZ ISM band, which may have a range up to 1 Km.. The main problem to be solved is the frequent bursts from other sources, and the continual noise pulses from the receiver. The transmitters provide short bursts with a format which may be used for any of the receivers. The action taken by a receiver then depends on the command in the message. This may be easily changed in the microcontroller program. Here is a discussion of the problems which were solved to get reliable control. This section is confined to a subset of transmitters which are manually operated and receivers which activate relays controlling line receptacles in NEMA enclosures. |
Transmitters |
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