Three batch fill/settle/draw electronic controller for use with a reverse osmosis unit

Abstract

An electronic controller for controlling the fill, settle and draw operations of three settling tanks which are used with a reverse osmosis unit. The three settling tanks provide a pair of liquid level input signals which indicate the water level within each of the three settling tanks. A bounce eliminator circuit eliminates oscillations from the input signals, providing at its outputs steady state liquid level signals which are active low. The liquid level signals are supplied to a programmable logic device which has a state machine. The state machine sequentially controls the fill, draw and settle operations of the three settling tanks. The programmable logic device provides logic signals which are active low and which activate fill and draw valves associated with each of the three tanks.