Help with Transistors and lights in time with sound

[PDoyle]

Hi all. 

For my project, I need to have the mouth of one of my characters illuminate in time with his voice.  Although it's feasible to program each flash manually, doing so would require an immense amount of patience and would likely eat up what's left of my Prop 2's memory.

My initial plan was to use a transistor hooked up to the audio signal to turn on and off the LED.  However, I have no confidence working with transistors and thought I'd consult the forum first.  I bought a few bipolar transistors from Radio Shack but I don't have the guts to put them in series with my speaker.  Am I going to blow out my amplifier?  Would I be better off with field-effect transistors and if so, where could I find them?

Thanks for your help.

-An expert of lesser experience

[JonnyMac]

You might to a web search for similar circuits; if memory (which can be shaky) serves me, I've seen them with little audio transformers to provide proper load to the amplifier.  On the other side you may want a bit of a buffer an a comparator circuit so you can set a minimum threshold.

[JackMan]

PDoyle,

      You may want to check this out, for 40 Bucks it will do a nice job for ya.


http://cowlacious.com/productPages/scaryTerry/scaryTerry.html

[menehune]

If you want to tinker with building a kit, you could get the VS1 voice activated switch kit from ramsey electronics.

http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=VS1

They provide a pretty good explanation of the circuit-like the old Heathkit projects.