This\r\n circuit indicates which of three voltages in the vary from about about\r\n -4V to about +4V - at A, B and C - is the very best by way of lights one in all \r\nthree indicator LEDs. Alternatively, it may be wired to point the \r\nlowest of three voltages or to indicate both the easiest and lowest \r\nvoltages. Op amps IC1a, IC1b & IC1c are wired as comparators, while \r\nthe three indicator LEDs and their series 1kO present limiting resistors\r\n are strung across the op amp outputs to put in force the proper logic\r\n operates.
Circuit diagram:
For\r\n instance, LED A will gentle only when pin eight of IC1c is low (ie, A larger\r\n B) and pin 7 of IC1b is excessive (ie, A higher C). Similarly, LED B will \r\nlight only when pin 8 of IC1c is high (ie, B larger A) and pin 1 of \r\nIC1a is low (ie, B better C). LED C works in identical fashion if the \r\nvoltage at C is the very best. Note that if the entire LEDs and their \r\nparallel 1N4148 diodes are reversed, the circuit will indicate the \r\nlowest of the three enter voltages. And if each and each 1N4148 diode is replaced\r\n through a LED, the circuit will indicate each the perfect and lowest enters.
Author: Andrew Partridge - Copyright: Silicon Chip
