Circuit that allows snap of fingers creates equal flash from LED?

Hello all!
I am just getting back into electronics, after taking a basic class 20 years ago. So it's like starting all over again.

I have a request for schematic advice:
The project I'm trying to design and build is a circuit that will flash an LED IN TIME with a snap of my finger, with a minimum of parts...and as miniturized as possible.

Can I take a electret mini-microphone and have it feed into the base of a single transister, and amplify that tiny signal enough to result in a coresponding flash of an led (based on a 4.5v circuit)? The trick is that I'm trying to build this whole unit (including the 3 button batteries) that will fit inside a micro-mag (single AA) flashlight housing. In other words, the entire assembly needs to be no larger than a AA battery type penlight housing...so I can't build a huge amplification circuit with many components.

So, (to sum it up) I'm trying to amplify a tiny microphone signal enough to light an LED, and use only a small number of components (that will fit inside a single AA cell flashlight).

Am I dreaming that this can be done with only one transister and a minimum of other components?

I want to have my (modified) "flashlight" sitting on my desk and "flash" at me when I snap my fingers (as if it was flashing at me to the snap of my fingers).

Thanks for any help or advice, folks!

Try this circuit:
**broken link removed**

The LED illuminates when the circuit detects a high amplitude waveform. It can be connected to a "Walkman" or mini radio with earphones. A second channel can be connected to produce a stereo effect. Circuit A consumes less current as the LED is off when no audio is detected. Circuit B pulses the LED brighter when audio is detected.

Add an electet mic (insert) via a 10k resistor for 3v to the input of circuit B.
Circuit A requires at least 600mV for activation.

Thanks, Colin. It looks like it would work, but I need it to be an even smaller design with less parts that will fit inside the space of a normal AA battery.

I don't know enough about transister electrical theory to fully understand how to use a single transister (or at most a darlinton pair) to amplify a weak electet signal into a full 4.5volt signal that will light the LED.

My "space limitations" are what really makes this difficult, and the fact that it has to be "sound activated" to the snap of my fingers.

I am curious if it can somehow be as simple as the drawing below (somehow) or perhaps at most a similarly arranged Darlington pair? Can the signal from an electet (or any tiny microphone) actually activate the base of a transister, or is the signal just too weak?

I have found the same basic simple schematic that worked for a "touch light" activation that used a darlington pair. You would think that if the voltage on my skin would be enough to activate it, then somehow the signal from a small microphone could also be used.

This is kinda what I'm trying to make work:
**broken link removed**

Is there a transister (as shown) that will activate on something as small as the input from a small microphone (shown in RED)?

Please also note, the LED that I'm using seems to like a full 4.5V, and is somewhat weak when using just 3V.



Can you guys see the picture when I'm NOT logged on? Here is a direct link to the album:
**broken link removed**

MOST important, I just want to say thanks for any advice, as I am just in the infancy stages of my learning...and what a GREAT site this is!!!

Colin, in circuit A above, can I safely change the voltage to 4.5V instead of 3V?
The LED I want to user is made for a 3 button battery setup (so 4.5V).

You mentioned that it requires 600mv for activation...is this possible directly from a small microphone? I don't have the room to have a walkman or mini-fm radio amplify the signal. So, I'm trying to find an application that can be activated by a small microphone itself.

Here are two circuits:

Colin, thank you! That should do it if I can get the parts arranged properly in the space available. Thank you for your time in answering my quandry. I had a hunch it could be done, but not enough experience to know for sure, or to size the parts.

Much appreciated!

You need to build the circuit and see if the microphone is sensitive enough to work with the sound (audio) you provide.

Will do! I can try to find a larger microphone (that will still fit) if that would help.
It doesn't necessarily HAVE to be a electet microphone, I was just trying to keep the whole package as small as possible. I will probably try the Darlington setup first.

Will the folks at Radio Shack know which Darlington transister I'll need if I show them the schematic? I have to learn a LOT more to understand how you sized the parts and determined the location of the capacitor (etc.) I guess it's time to get back into a college class or something.

Electet microphones give the highest output and they can be over-driven by decreasing the load resistor - as you don't need clear, clean, audio.

Sweet! So it's just a matter of playing around with the values.
You are also right in that I don't need clear clean audio...just something that will amplify the snap of my fingers to flash the LED.

Again, Colin, I thank you for your time.
What a great site!

I have had such good advice on this project, I've come up with another.

My next project is going to be a Television Audio volume regulator to keep my TV output at a constant volume. I cannot BELIEVE the way that the networks are allowed to CRANK to volume levels on the "commercials" to double and triple the volume that you have set the "show". But, I'll start a new thread for that one.

Thanks again, Colin!

The TV stations already use a volume limiter. It limits the peak volume so that the average volume is much higher. It is called an audio compressor.

Thanks Audioguru. I went ahead and started a new thread for the TV Volume limiter. But, you have brought up another question...I'll ask it in the other thread >>

(thanks!)

I turn off the sound as soon as I hear a commercial. I have not heard a commercial for 40 years. I also shut my eyes.
Commercials are indoctrination, and indoctrination is very bad. It’s a form of brainwashing and that’s why I will never listen to anything that is repeated.
I suggest you devise a circuit that turns the sound OFF when it is louder than the rest of the program.
In fact, the way they get around the legislation is to output the movie at a lower level and have the commercials at the max level allowed. This way you turn up your volume control and get the result of loud commercials.
I defeat this by never listening and obviously never buying.
In 40 years I haven’t missed anything.
I have thought about this for many years. Now that TV’s have remote controls, the best way is to create a circuit that monitors the audio and turns the sound down to a very low level and then turns it up again when the commercial has finished.
If you place a coil over the front of one of the speakers, you will be able to monitor the sound without touching the set, if it doesn’t have an “audio out.”

I turn off the sound as soon as I hear a commercial. I have not heard a commercial for 40 years. I also shut my eyes.

Click to expand...

WORD on that Bro! I'm just getting tired of the loud BLAST before I can reach the "mute" button!

Thanks for the help on this LED flasher circuit! I'm anxious to get the parts now, and see if I can get it worked out.

The commercials have their average sound level boosted with an audio compressor.
The movies and talks shows also.
What is not compressed? Sports games?

There have been many muting circuits. They mute when the TV fades to black before a commercial. Or a night scene. Or between scenes in a movie. Usless.

Sorry to get slightly off topic but have you considered hacking a Clapper for your project?

Circuit that snap of fingers flashes an LED

Yes, but I believe the clapper circuit probably has too many parts, and I'm trying to fit the entire circuit (including the 3 button batteries) into the normal AA battery compartrment of the LED flashlight. So, I've probably got enough space for a simple transister (or darlington) amplifier circuit...
I just didn't know if the small microphone would provide enough to the transister's base to activate the transister.
**broken link removed**

But the circuit shown (below) by Colin seems to be pretty close to small enough. I am anxious to get the parts and get it built!

The circuit does not have enough sensitivity. You must scream at the mic or hit it with a hammer for the circuit to do anything.

Actually, the LED is turned on all the time which will kill the tiny battery in a few minutes.

The first transistor is biased so poorly that it is a thermometer that turns off the LED when the first transistor gets warm. But when it is warm then the first transistor is turned on which will kill the tiny battery in one hour.