Good Day,
I was trying to build a VU meter for my audio circuit. Basically, when I have a louder sound, more leds turn on. My design looks something like this: And yes it works, but I just want to verify my theory.
- Well, basically the signal comes into the op-amp which amplifies it about 10 times, before going to the LED array.
- But for the second part, does it work such that when there is more voltage (louder-greater amplitude) coming out, it causes the diode to go into reverse voltage, and hence lights up the LED via the BJT? So with an even louder signal, the next diode is bypassed as well, causing the last LED to light up?
Best Answer
You need to have followed the original instructions given to you: -
Here
It clearly states in that answer that you need to use a rectifier circuit. This is to convert the AC signal from the amp (or signal inputted) into a positive dc value whose peak level is roughly proportional to the peak of the AC signal.
As a matter of curiosity, if you took out the BJTs and replaced each of them with a short from base to collector does it still work? If so then you've either used PNP transistors or incorrectly wired them to the circuit.