Independent control of two solenoid operated valves over two wires in an irrigation system

摘要

Apparatus 11 and 13 for interfacing two AC sources with two AC loads 17a 17b in the form of solenoid operated valves over a single conductor 25, with a return conductor 19 in an irrigation system is disclosed. The apparatus has an encoder circuit 11 with two inputs 21a 21b for connection to the two AC sources, and an output 23 for connection to the single conductor 25, and a decoder circuit 13 having an input 27 for connection to the conductor 25, and two outputs 29a 29b for connection to loads 17a 17b respectively. When the first input 21a is powered, the first load 17a will be switched on, and when the second input 21b is powered, the second load 17b will be switched on. The decoder portion 13 incorporates switching circuits 43a 43b, interfaced with turn on delay timers 45a 45b respectively, to delay operating the loads at switch on, and turn-off delay timers 47a 47b to hold the loads on after switch off.

主权项

1. A duplex encoder/decoder pair for interfacing a first current source and a second current source with a first load and a second load over a single conductor, comprising an encoder portion having a first input for connection to said first current source, and a second input for connection to said second current source, and an output for connection to the single conductor, and comprising a decoder portion having an input for connection to the conductor, a first output for connection to a first load and a second output for connection to a second load, where the encoder portion is adapted for selectively conducting current from the first encoder input to the encoder output and alternatively the encoder output to the second encoder input, and the decoder portion is adapted for selectively conducting current only from the decoder input to the first decoder output and alternatively from the second decoder output to the decoder input, the decoder portion also incorporates a first switching circuit between said input and said first output, interfaced with a first turn on delay timer to time out a predetermined period before operating said first switching circuit, and a second switching circuit between said input and said second output, interfaced with a second turn on delay timer to time out a predetermined period before operating said second switching circuit, the first decoder output and the second decoder output each including a turn-off delay circuit, each turn-off delay circuit comprising a diode and capacitor connected in parallel, connected in series with an inductor, which when in circuit is connected across the load which is connected to the relevant output.