So I need to make an LED grid.
The input will be an constantly changing analog signal (whose voltage ranges I don't know yet). I need to rectify the signal (convert all the negative voltages to positive), then I'd like to light up a different number of LEDs based on the value of the rectified signal. If it's low voltage (but higher than zero), then I'll want 4 (or maybe 6 or
of some color LED to light up (say blue). At a slightly higher voltage, I'll want the 4 blue LED's to light up, but also 4 more LEDs (say green) to light as well. At a slightly higher voltage, I'll have the 4 blues, 4 greens, and 4 yellows (or whatever color) light up. I'd like to have at least 4 different stages (each stage being 4 more LEDs light up), and this needs to be voltage regulated (I don't want to blow the blues, when I have a high enough voltage to turn on the yellows).
The input voltages will be changing pretty fast, so ideally this needs to be pretty responsive.
Because this is a school project, I need to be able to build as much of this as possible with just basic components (R's, L's, C's, transistors, op-amps, diodes, etc) as opposed to just buying ICs which do everything for me.
I figure I can rectify it with something like this
at the front, I should be able to use switches with varying resistors to turn on each new set of LEDs, but how do I regulate the voltage so that I don't blow the first stage (blue) LED's when I turn on later stage (yellow) LED's?