![]() ![]() A small/cheap microcontroller with some non-volatile, reprogrammable memory plus a few analog components. Analog electronics to demodulate the signal from the AC carrier on the 2-wire cable that runs to all valve drivers plus digital electronics to interpret valve commands. Maybe this could simply be a serial-to-2-wire converter that could be added to the OD hardware as an option.Ģ. Use whatever serial protocol makes sense – async serial as used in the RS-232 standard would work fine. Add a serial-to-modulated power interface to the OS controller hardware. Seems to me that if OS used an existing 2-wire protocol that would work BUT adapting an exiting serial protocol to OS plus a simple/cheap design for the valve solenoid driver would be straightforward – and avoid potential patent infringement For example:ġ. The controllers themselves are over $1000. Looking online, I see 4 valve solenoid driver for $240. It is ridiculous that a 2-wire valve adapter is more than $60 per valve (and often much more). I think the main problem with commercially available 2-wire systems is the high cost of components. Commercial systems cost many thousands of dollars. Typical systems can address hundreds of valves. Commercial systems uses a dedicated (expensive) programmer for this purpose. Some method must be provided to program the station address into the solenoid controller. Each solenoid driver has to have a unique “station address” to enable each solenoid driver to be uniquely addressed. So the solenoid driver extracts a stream of command data and 24 VAC power. The electronics in the solenoid driver demodulate the data riding on the 24 VAC power and provide switched power to the valve when that particular solenoid driver is addressed by the system. For example, clip one positive cycle of the 24 VAC waveform at half amplitude for a ‘1’, clip the negative half of the 24 VAC waveform for a ‘0’. Some implementations clip a portion of the AC waveform to indicate a digital ‘1’ or ‘0’. Modulated onto the 24 VAC power is signal that implements a communications protocol designed to talk to a solenoid driver located at each valve station. The number of valves add up quickly.įirst, a small amount of background on 2-wire:Ģ-wire is a generic term for systems that employ a single pair of wires to drive all valves in the irrigation system. I have lots of trees that need irrigation, and in practical terms this means one valve per tree. I too am very interested in 2-wire system since I have a lot of valves spread over a lot of area and don’t want to run lots of wires or multiple controllers.
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