Help with a sound-actived LED

[Mikebits]

That makes sense.

 

[PerfectNeglect]

I would really appreciate that-- I just need to know what I need and where to put it, and I should be able to assemble everything. That said, the light would (ideally) be off unless she was speaking. Since this is a recreation of a costume, I'm aiming for keeping it as accurate as possible. This is an example of what I need it to do.

Thank you again, everyone, for helping me with this.

 

[Mikebits]

Okay, this is what I came up with. I only simulated it, have not built this before so no guarantee. Attached is a simulation I ran using a voice file as the input.
You can see the PWM varies with the voice which should brighten or dim the LED. You can substitute the JFET if you have trouble finding the one I used, just make sure it has a VGS of 5v or less. I also used a 5v regulator because the circuit would not function properly as the 9v battery dropped.
I included the netlist which should tell you what to connect. May be easier than following the schematic. It has been a long time since I have done electronics, so best if someone from here has a look at my circuit before you build it. Anyways, I hope this helps.

 

[audioguru]

Very nice (but fairly complicated), Mike.
Doesn't your SIM program know that the minimum supply for a TL071, TL072 and TL074 is 7V?

 

[Mikebits]

Ah crap, thanks for spotting that. I will have to pay more attention, I started out with 9v and later changed that, maybe I ran the sim with 9v, but I can't remember. I will have to make a update and upload a corrected schematic. Glad you caught that, I'm such a dope.

-----------------------------------Edit---------------------------------------------------------------
Okay I made a change to the original schematic file. The revised schematic is in the original post I made. I will post the corrected version here as well. The netlist remains the same as the pin out of the new opamp is same as previous. I tried to pick a common easy to get part. The opa is a LM358 8 pin dip. Data sheet is here:
https://www.mouser.com/ds/2/405/lm358a-557593.pdf
Thanks AG

 

[audioguru]

The LM358 is not an audio opamp, instead it has low power. Therefore it has a lot of noise, produces crossover distortion and has trouble with high audio frequencies.
If the actor says, "She sells seashells on the seashore" then the LED will show, "Rumble hissss, Ee ell ee ell on uh ee or, rumble hissss" (vowels only, no consonants). Maybe a little exaggerated, but I am an audio guy and I hate the LM324 and LM358.

 

[ericgibbs]

hi guys,
Have you carefully watched the video the OP posted earlier, post #22, its a VERY basic voice On/Off LED.

Mike's circuit is interesting but overly complex for this App, IMHO.

E

 

[Mikebits]

This is the ultra simple version, but should still work for what you need. I also found another error in the original circuit and went ahead and corrected it.

 

[audioguru]

The input resistance of the extremely old comparator is not listed in the datasheets but it is probably higher than requiring a huge polarized input capacitor of 33uF for audio. Maybe a 0.33uF unpolarized film capacitor is fine.
I notice that your input capacitor in both schematics has its polarity backwards.
The (+) input of the comparator is floating with no reference voltage (half the supply?) and since it is a PNP transistor then it will float high.

 

[Mikebits]

Well, I will get to it later.

 

[large_ghostman]

actually when you watch the vid it dosnt really sinc at all, I hope this isnt being turned into a stage play! awful acting

 

[PerfectNeglect]

Thank you, everyone. Sorry if this is a headache-- I really appreciate the help.

 

[ericgibbs]

Well, I will get to it later.

Morning Mike,
I would suggest that you add the 'bits' at the front end of your circuit for the OP's electret microphone [ he posted a link earlier]

Eric

 

[Mikebits]

Okay here is latest. I'm done making changes.

 

[audioguru]

Without a preamp the latest sound-activated-LED circuit should work fine when the speech is at a steady level. The two voltage dividers will track as the battery voltage runs down so a regulator is not needed.
It might be difficult to set the trimpot so that the LED flickers with speech because the mic output will be about 20mV RMS with a peak at about 28mV.

 

[Mikebits]

Thanks AG. My Karma account was getting low, so I just wanted to help the guy out. Hopefully it will give him a reasonable visual effect for his costume. I have other things on my plate so I was not able to put a lot of time into it.

 

[Mikebits]

Now that I did this I bet the guy won't even bother with it, or he may have already moved on.

 

[audioguru]

He will come back to say that RadioCrap does not have any of the parts on your schematic so the actress will use a hand operated flashlight.

 

[PerfectNeglect]

Er, neither of those things...? Thank you for all of your help, though. I apologize for being somewhat late in replying, work has been a bit demanding. Again-- thank you for the help.

 

[Mikebits]

Having heard that there were purple LED's, I just had to see one for myself, so I went and bought a few. They looked more blue than purple to me. One interesting thing is the lens flare from my camera is purple. Here is a couple pics. My iphone is not good for shooting light but one can see the LED reflection on the pwb is blue. I wonder if that guy ever got his project done?
The lens flare looks pretty cool.