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Moving-Dot Display Driver [140111]

Status: Finished
April 24, 2014

A simple circuit to create a moving dot display from a voltage similar to an LM3914 but with a programmable voltage divider so it is not limited to linear or logarithmic scales.

Four comparators cut the input signal range into five sub-ranges. An LED is lighted when the input falls into the corresponding sub-range, but the LEDs in the sub-ranges below and above will remain off, i.e. only one LED will light at any time.

When two consecutive comparator outputs are both low or both high, the PNP transistor between them will block because its base and emitter see the same voltage level and the LED connected to the transistor will be off.

Only when the upper comparator output is low and the lower comparator output is high will the transistor conduct and will the LED be on.

P1 allows to scale the sub-ranges. Recalculate the voltage divider R5 to R8 to fit it to what you need. Idem for the input filter.


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