Sections of RS339 quad comparator each drive LED to give indications of four different input voltage levels, While LED 1 is connected to ground for use as zero indicator Resistors shown are for Radio Shack 276-041 red LEDs ›change R6-R9 to 270 ohms and R1 to 470 ohms for green LEDs Pot R1 is used to calibrate voltage divider R2-R5 With R1 set all
ow resistance, comparators turn on at intervals of 1 V or more With high resistance for R1, comparators turn on at fractional-volt intervals. F. M. Mims, Integrated Circuit Projects, vol. 4, Radio Shack, Fort Worth, TX, 1977, 2 nd Ed. , 76-85.