LM3915 LED display driver
At least a couple of years ago I took delivery of LM3914, LM3915 and LM3916 LED display driver ICs.
The most common application for these devices is to drive an array of LEDs in response to an input (e.g. sound), to make a digital version of the analog VU-meter shown below.
The LM3914 can process an analog signal in a linear fashion, the LM3915 operates the same but in a logarithmic manner, and finally the LM3916 is logarithmic and has been specifically optimised for audio applications.
I found quite a few different circuits online which described the usage of this chip, and had couple of false starts as a result.
In particular, the microphone works w-a-y better with a simple amplifier between the microphone and the chip, and for that I used an LM358 OpAmp circuit as shown below.
The final result works so well it has rather unusually sat on my bench for a few days for fun, normally I dismantle such circuits pretty quickly. In fact is part of an intro for a future mailbag. Nice one!
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