BAR GRAPH READOUT VOLTMETER

Description: Sections of the RS339 quad comparator each drive an LED to indicate four different input voltage levels. LED 1 is connected to ground to serve as a zero indicator. The resistors depicted are intended for Radio Shack 276-041 red LEDs; it is recommended to change R6-R9 to 270 ohms and R1 to 470 ohms when using green LEDs. The potentiometer R1 is utilized to calibrate the voltage divider formed by resistors R2-R5. With R1 set to low resistance, the comparators activate at intervals of 1 volt or more. Conversely, with high resistance for R1, the comparators activate at fractional-volt intervals.

The described circuit employs the RS339 quad comparator, which is a versatile device used for comparing input voltage levels. The circuit is designed to provide visual feedback through LEDs corresponding to the voltage levels detected by the comparators. Each comparator output drives an LED, illuminating them based on the input voltage conditions.

LED 1 serves a critical function as a zero voltage indicator, providing a visual cue when the input voltage is at ground potential. The choice of resistors is important for ensuring the correct operation of the LEDs; for red LEDs, the specified values are appropriate, while adjustments to 270 ohms for R6-R9 and 470 ohms for R1 are necessary when green LEDs are implemented to maintain the desired brightness and response characteristics.

The potentiometer R1 allows for fine-tuning of the voltage reference levels. By adjusting R1, the user can set the threshold at which the comparators activate, either at regular 1-volt intervals or at more granular fractional-volt intervals, depending on the resistance setting. The resistors R2 to R5 form a voltage divider that works in conjunction with R1 to set the reference voltages for the comparators.

In summary, this circuit is a practical application of the RS339 quad comparator, providing a straightforward method for monitoring and indicating various input voltage levels through visual means. The calibration feature via the potentiometer enhances the circuit's flexibility, making it suitable for various applications where voltage level indication is required.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.