Hi! First off, thank you so much for any help. I am slowly learning electronics and arduinos etc... maybe one day I will be smart enough to help people on here.
I arranged it all on a breadboard and I thought I did everything perfect...
I am powering the circuit by the 5v from the arduino.
The output (0-3v) is connected to an led. presumably the led should turn on when the circuit detects sound.
It does not turn on at all no matter what sound is made. I have tried changing the sensitivity of the two potentiometers. I have also hooked up the output to a multimeter.
it reads 0.52v no matter what sound is made or setting of the potentiometers.
Here is a high quality picture of the set up. Since some of the pins under the transistors and capacitors cannot be seen, I drew them in orange: http://i50.tinypic.com/r877r6.jpg
power it up for the first time through a 100ohm resistor, and measure the voltage over that resistor: this assures you if there is short.
you need to make sure that the dc working points are correct. Measure voltage on Q1's b / c, Q2's b/e/c, Q3's b/e. and compare them to what you expect. For example, Q1's b should be about 0.7v, Q2's b should float with RV2, etc.
if you have a scope, it would be helpful but get the dc working points and report back.
power it up for the first time through a 100ohm resistor, and measure the voltage over that resistor: this assures you if there is short.
you need to make sure that the dc working points are correct. Measure voltage on Q1's b / c, Q2's b/e/c, Q3's b/e. and compare them to what you expect. For example, Q1's b should be about 0.7v, Q2's b should float with RV2, etc.
if you have a scope, it would be helpful but get the dc working points and report back.
ok,
I measured the voltage over a 100r resistor in place of the led. It was 0v. I asume this is what you mean telling me there is a short.
-i measured the voltage across q1. it reads 0.230mv from c-b, 0.6v from b-e and 0.85v from c-e.
-q2: 4.5v from c-b, 5v c-e, 0.5v b-e
-q3: 4.8v c-b, 5v c-e, 0v b-e
So Q1 is conducting, at about 0.8ma Ic. That's good.
Q2 is not conducting: RV2 is too small so you will need to raise the wiper towards the top (the rail).
As Q2 is not conducting, Q3 is not conducting.
the voltage I was talking about was the respective points vs. ground.
i meant from the output (0-3v) to the ground.
oh ok, sorry.
q1: b = 0.63v c = 0.86v
q2: b = 4.5-6.5v (depending on sound) e = 5v c = 0 - 3.5v (depending on sound) (the led lights up to sound from this pin to ground, but it doesnt have the slow decay which i am assuming is what the next transistor is for)
q3: e = 0v (no matter what sound), b = 0v (no matter what sound) c = 0v (no matter what sound)
so I am assuming the problem is somewhere around the last transistor...
OP, after you learn how transistors work, the next step is discovering that opAmp circuits
are a much better way to go, in general requiring far fewer components, and producing much
better results with a lot less effort,