Motivation

Voltmeter faceplate

The circuitry of this module was developed by Ray Wilson of MFOS. It was part of his Multi-Function Module. I have changed some resistor values to use with low current LED.

The LED voltage level meter gives you a graphical idea of where the voltage level you like to use to modulate your filter or VCA is. This circuit lights the LED in real time giving you a rough idea of the voltage level you are looking for. This is very useful when you want to move a CV from bipolar to only positive values.


Specs and features


Implementation

Schematic

Voltmeter schematic

Voltmeter schematic


Description:

IC4A is used for input buffering. IC4B and IC4C and associated components build the range selection circuitry. The heart of the circuit is the group of comparators build with IC1x, IC2x, IC3A and IC3B. The left side is used to measure the positive voltage, the right side for the negative voltage. LED 11 is the "near ground" indicator. IC3C and IC3D build a window comparator. For a more detailed description please refer to the original source at Ray Wilson's Site MFOS (Multi-Function Module).


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Calibration

With the range switch in mid position (1V range) adjust TR1 for 1V at pin10 of IC4B.

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Special parts

None

Download

Voltmeter documentation download


Voltmeter populated PCB

Voltmeter: populated PCB


Voltmeter side view

Voltmeter: side view


Voltmeter front view

Voltmeter: front view


Voltmeter back view

Voltmeter: back view


2018 October V. 0.9.0

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