Speaker output voltage test

[Guido]

Hi folks,

 

This is a bit of a weird one, I'm trting to use a speaker signal to switch a transistor, more precisely, using the speaker signal from a set of cans to switch a transistor.

 

Is it possible and how would I go about finding the output voltage? I've already got a base reading from the headset speaker pins on theobelt pack of 5mv, but this doesn't seem to fluctuate at all when a sound is applied to the com's. Is it jjust that my meter isn't sensitive enough?

 

Any help is appreciated

 

Ta

[stu00c]

If you are measuring voltage on speaker lines carrying normal audio signals, you will need a true RMS meter.

 

Stu

[Oldradiohand]

...and some meters won't measure small AC signals anyway. Do you want a voice operated switch? 'cos it's a little more complex than driving a transistor with audio. There's a load of simplish circuits out there for amplifying, rectifying and driving switching transistors, just google "voice operated switch".

[sleah]

...and some meters won't measure small AC signals anyway. Do you want a voice operated switch? 'cos it's a little more complex than driving a transistor with audio. There's a load of simplish circuits out there for amplifying, rectifying and driving switching transistors, just google "voice operated switch".

That sounds very much like the little "sound-to-motor" circuits you often found in halogen disco effects, such as the infamous Martin Ministar.

Or dare I suggest, a single channel sound-to-light unit!

[sclg]

The headphone output is a low level audio signal.

Conventionally, you'd stick that through a simple op amp circuit to amplify, rectify and smooth it then stuff the output of that into a transistor to switch whatever you are trying to switch.

[Guido]

Thanks guys, I appreciate all the help!

I'm sure I'll be back with more questions as the project progresses, but you have put my thoughts on the right path for now!