How it's possible to turn on/off a single LED with the left (or right) sound channel of an audio jack and a pnp transistor.
Everywhere npn transistors are used. Like here:
I'm very new to this topic and need the led control for a simple project of my computer science master thesis. My uncle gave me some old pnp transistors and I built something like this: and this: .
When I use my fingers the LED glow. But when I connect my audo jack and play a song, nothings happens or the LED glows very very (not visible) low. I thought, that the 5V will give the power although the audio jack has not enough power.
Are npn transitor needed or is there a very simple way to use pnp transistor to let the LED glow, when a smarthone plays a sound throuh the audio jack? A simple circuit diagram would be helpful.