4

LED ‘graph’ circuits

The previous two chapters took detailed looks at LED principles and at various practical LED visual display circuits. The present chapter continues the LED display theme by looking at a variety of practical LED dot-graph and bar-graph analogue-value display circuits.

LED ‘graph’ displays

One of the most popular types of multi-LED indicator circuit is the so called analogue-value indicator or ‘graph’ display, which is designed to drive a chain of linearly spaced LEDs in such a way that the length of chain that is illuminated is proportional to the analogue value of a voltage applied to the input of the LED-driver circuit, e.g. so that the circuit acts like an analogue voltmeter.

Practical graph circuits may be designed ...

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