How can I add an LED to my Neovibe that blinks w/ the pulse?

[Chris Goodson]

I tried hooking one up in the circuit(can't remember where right now) and it seemed to rob too much power from the lamp.  Could someone please help me figure out how to do it without any problems?

[Jason D]

http://www.lynx.bc.ca/~jc/pedalsUnivibe.html


This might help, might not. Scroll down the page were it has the speed indicator led mod.

[brett]

Try using a transistor as a switch/amplifier.  Connect the base of an NPN tranny to your LFO (or other) signal via a high value resistor (e.g. 10k).  The emitter goes to ground.  Put your LED and a current limiting resistor (e.g. 1k) between the collector and the +9V supply.  When the LFO output is above 0.6V, the LED will light, below 0.6V it will be "off".  You can set the LED to turn "on" at higher voltages by using a voltage divider to reduce the source voltage. e.g. tapping the middle of two similar resistors (e.g. 1k) between the source and ground will double the voltage at which the LED turns on (ie 1.2 V).

I hope that helps.  Ask again if this needs clarification.