LEDs and the Really Cheap Compressor

[Lee]

Hi, I just tried building this compressor this morning, but I'm sure there's something not gonna work out.

First, when I connected it to a battery, the two LEDs just quickly blinked and never lighted up. Then I reconnected the battery, same thing happened again.

But the circuit did produce sound as I covered the LDR, the volume increased and uncovered the LDR the volume dropped.

The battery and the LEDs were fine.

Could someone figure it out?

Many thanks.

[induction]

The leds don't visibly light up in this circuit.  They're part of a negative feedback loop: the louder the signal, the more they light up, which decreases resistance in the ldr, which reduces the signal gain, which reduces voltage to the leds, which makes them light up less.  In practice, you'll never see much light coming out.

Sounds like your build is working just fine.

[GoranP]

Well Henry  , you are definitely a welcomed addition to the bunch here!

Nice to have people who know their stuff...

[Lee]

Finally I can go to bed with relief tonight.

Gratitude to induction!

[induction]

Thanks.  I'm glad I could help.

Let us know how it comes out, Lee.  I like mine a lot, but found that it cuts a lot of treble.  I made a version that adds a bright mod on a toggle switch.  You can read about it here, if you're interested.

[Lee]

I built the bass version so there's not too much cut on the treble. It was not that obvious unless I am being picky about that.

I made a video to show how the LEDs worked, just in case there's someone who might be confused like me. Sorry for my crappy English, I'm Chinese and English is my second language.

http://www.youtube.com/watch?v=wXSBB6JxMNY&feature=youtu.be


Actually I don't think compressor is the kind of effect that you can tell as soon as you hear the notes. So I reckon the best way to see how a compressor works is by showing its wave.

Here's a picture that I recorded:



And this is my build:



Thank you again for helping me make sure I built the correct one.

[Madferret]

Hey, you might want to put some heat shrink tubing around the LED, LDR pair as that will make sure it works to it's full potential in all conditions.  I just cut a short length and push the LED/LDR in from each side until they meet and then use a hairdryer on it until it shrinks into place and form a nice seal around the pair.

[Lee]

Great！

I was planning to wrap the whole circuit with electrical insulating tapes. But thanks for your advice!

[GoranP]

That works just as good. Been doing the electrical tape for a while now and I have no reason to change.

No need to wrap the entire circuit, just the led/ldr combo.

[Lee]

Thank you guys who have helped me with my questions.

Here are some pictures of this compressor, which I named it "Night's Whisper Compressor".

The reason why I drew an abstract painting on it is because compressor is that kind of effect that you can hardly tell "is it on or not". But just like an abstract painting,  the effect is abstract too. It has its own beauty and once you get the essence of it, you'll love it and never wanna switch it off.


The blue light indicates on or off, and the red one reflects the amount of compression, just like those ones in the circuit.

Here is a demo: http://www.youtube.com/watch?v=btHsUE7F9Ig

I love this compressor. It limits those excessively loud sounds, so you don't have to worry about slapping after finger playing. The volume will always stay under your limitation.

Thanks again.