Hi, I am building a project where a single LED(or several LED in parallel) is expected to behave like a VU meter. I would like the brightness of the LED to represent the loudness. Accuracy is not important but at least I need logarithmic indication. I would like to know what is the most elegant way to achieve this.
First, the famous LED bar driver LM3915 came to my mind. I think maybe I can combine all the output pins and connect them to the cathode of the LED, then limit the current of each pin to around 1mA. Maybe this would allow the LED to have 10 steps of brightness from 1mA to 10mA. But here's the problem:
I observed the Vmax of my audio signal is around 300mV. According to the datasheet's example configuration, the IC's high reference voltage(when all LEDs light up) can be adjusted down to 1.25V. Must I feed the IC with the amplified signal? It requires extra components and space. Or maybe I can set Vref down to 0.3V, but would it cause unbearable bad accuracy?
I don't know if using an IC is overkill, but I haven't found a discrete solution with logarithmic support. I would be grateful if you can give me some direction.