Inexpensive Remote Watering System

Posted on Feb 6, 2014

This remotely controlled watering system is both inexpensive and easy to expand. It is designed to operate in conjunction with a conventional watering timer and allows remote switching between nine zones. The prototype is used in a bore system, where a deep-well pump must be started and kept running while zones are being changed. This is necessary

Inexpensive Remote Watering System
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to minimise cycling and results in maximum pump life. A standard portable telephone is used as the transmitter and receiver. The system`s range is therefore limited only by the telephone specifications. The prototype uses an Audioline model CDL1A, set to pulse-dial mode via a switch in the side. Selecting zones from the telephone keypad couldn`t be simpler. For the first nine zones, each key number (1-9) corresponds directly to a zone number. If additional zones were added to the basic circuit, "0" would represents zone 10, while further zones are "dialed-in" by simple addition. For example, to select station 15, you`d press "0" and then "5". Looking now at the circuit, the telephone base station is wired to one input of a hex Schmitt-trigger inverter (IC5a), which functions as a low-pass filter and pulse shaper in conjunction with two 1kO resistors, a 10 µF capacitor and a second inverter (IC5c). Glitch-free pulses are fed to the clock inputs of two 74HC164 8-stage shift registers (IC3 & IC4). The A & B inputs of IC4 are permanently pulled high, so the first pulse results in a logic high at output O0 (pin 3). Each additional pulse causes the next successive output to go high. After eight pulses, output O7 (pin 13) goes high and this is propagated to the second shift register (IC4) via its A & B inputs. The shift register outputs are wired to a collection of 74HC86 exclusive-OR gates (IC6-IC8) in such a way that only one...

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