glowing and dimming LEDs with a transistor

Thread Starter

michael page

Joined Oct 29, 2013
Hello folks, Im making a project that requires a pair of LEDs to glow and another pair to dim upon receiving an envelope signal from a synth. I have breadboarded a circuit that works where a npn transistor receives the signal allows a pair of LEDs to glow, then an LDR's resistance drops shorting a second pair of LEDs making them fade out.
It works pretty well but seems like it might screw up the LDR quite quickly. Is there a better way of doing this?

my current diagram...


Joined Sep 9, 2010
If it works, I don't see a problem. The LDR is connected to the battery thru 12kΩ of resistance. As long as this is within the specs of the LDR, it'll be fine.