Led triggered by sound

[Mixerman]

This is my first post! I am new to electronic's, I have a radio shack learning lab, only done a few things with that!

Would this project be a good one for my learning lab?

http://www.aaroncake.net/circuits/steth.asp

Most of the threds I have read are people wanting to detect heart beat!

What I have in mind is a little different I don't know if it can be done the way I want it to.

I want to detect the clicking of a fuel injector coil going off an on! I don't want to listen , just the LED blink is fine.

In the plans there shows a OPTION to add LEDS! Could I just build that and eliminate the head phone part of the plans?

I would also like to have a prob to reach into a running engine and touch hard to reach injectors for the sound pickup.

Any help with this?

[rossw]

What I have in mind is a little different I don't know if it can be done the way I want it to.

I want to detect the clicking of a fuel injector coil going off an on! I don't want to listen , just the LED blink is fine.

Are you going to hear the sound of the injector over the sound of the engine?
I'd be thinking more of using an inductive pickup and putting that right by the injector coil and detecting that, probably much more immune to noise.
Downside is - if the injector COIL is working, but it's all gummed up inside and not actually operating, you wouldn't pick it up this way.

[WooferHound]

Yes ,  it will work without the headphone output but I think it would help you to have headphones more than you would think.
A couple of things to consider about this circuit . . .

• It does not include a sensitivity adjustment and it's probably too sensitive for the volumes that you want to sense
• It looks like the LEDs will display the audio just as you would hear it, might be helpful to have some threshold adjustment so it would only light up on the volume peaks
• An electret mic is very sensitive and a bit fragile, might try a piezo element but watch out for some High Voltage output from them which will destroy the opamp

That's all I can think of now
Nice project idea

[Mixerman]

What I have in mind is a little different I don't know if it can be done the way I want it to.

I want to detect the clicking of a fuel injector coil going off an on! I don't want to listen , just the LED blink is fine.

Are you going to hear the sound of the injector over the sound of the engine?

Yes!
I have a harbor freight Stethoscope now! No problem hearing the injector click over the engine noise, its much louder! I just dont like wearing the thing around moving parts or 100K volts!

As for the frequency of the click sound compared to a heart beat I have no idea!

[Mixerman]

Yes ,  it will work without the headphone output but I think it would help you to have headphones more than you would think.
A couple of things to consider about this circuit . . .

• It does not include a sensitivity adjustment and it's probably too sensitive for the volumes that you want to sense
• It looks like the LEDs will display the audio just as you would hear it, might be helpful to have some threshold adjustment so it would only light up on the volume peaks
• An electret mic is very sensitive and a bit fragile, might try a piezo element but watch out for some High Voltage output from them which will destroy the opamp

That's all I can think of now
Nice project idea

I've reading about the Piezo ele devices! I had no idea! there everywhere!

http://www.mide.com/pdfs/vibration_harvesting_conference_2008.pdf

I butchered a buzzer out of a PC mother board last night! I'll have to look more in the junk pile!

[MadScientist267]

Having issues with the inputs on the second op-amp in that circuit...

Why is there a cap (C3) in the positive feedback path if the goal is to filter the highs out (C4)?

Steve

[Mixerman]

I'M really not tied to this set of plans! But its the only one I could find that included LED's, it took me 2 days to find it. I seen alot of different plans for such things as LEDS dancing with music, that sort a thing! I would like to keep this a small device. Won't be doing any dancing!!!!

[WooferHound]

If you use a piezo. Put at least a 1000 ohm resister in series with it to control the voltage.

[Mixerman]

I did some expermenting tonight! I hooked my meter up the buzzer and stuck a nail in the hold for sound to come out, then placed the nail into my running drill. The output was AC,about 6.0MV was all I could get.

[WooferHound]

Sound is a very small voltage in the beginning

[Mixerman]

Did a little more today

 From the circuit descritpion:

• U1b operates as a low-noise Sallen and Key, Butterworth low-pass-filter with a cutoff frequency of about 103Hz. R7 and R8 provide a gain of about 1.6 and allow the use of equal values for C3 and C4 but still producing a sharp Butterworth response. The rolloff rate is 12dB/octave. C3 and C4 can be reduced to 4.7nF to increase the cutoff frequency to 1KHz to hear respiratory or mechanical (automobile engine) sounds.

 I have a sepehoscope from harbor freight I can just place it on the running injector and hear it "snap" on problem!
I dont like wearing it around moving parts and 100K volts!!

Some of these injectors are hard to get to! Infact some engine dis-assembly is required to get to them, and thats just to check them for mechanical movement. Doing this with a prob using sound or light short-cuts this whole process, for the shade tree DIY'er!

I did some experment today with a (portable phone) earphone,I hooked the ear phone to my meter and a red LED , when I tapped the earphone the LED blinked dimmly and got a reading of about 29.0 MV, AC, used a min-max meter. Tap  was more like a slap!

Thanks for your thoughts!

[WooferHound]

Any small amplifier can power an LED directly, and the volume control will adjust the brightness.
Try searching for Infrared Audio Transmitter, build that but use visible LEDs instead of Infrared LEDs.

[Mixerman]

I searched for it and found it! Its got a transmitter and reciever it ! Maybe its not the one you mean!

I have some plans that came with the RS learning lab, one of the plans is to "Build a super sentive op amp audio amplifier ( to listen to ants), this one also uses a speaker though!

Thanks

[WooferHound]

You don't need the receiver. Just the transmitter.
The opamp will not need to be sensitive. Just substitute LEDs for the speaker.

[Mixerman]

I put together most of the project today! Afew more options to add! If intrested its on page 74,75.76.
http://www.radioshack.com/graphics/uc/rsk/Support/ProductManuals/2800027_P1_PM_EN.pdf

For my bench test I placed the piezo pickup face down on the table, about a foot away I ran the portable drill resting on the table (eng noise mockup), about 2 foot from that I placed a 12v relay from a car on the table, (injector noise mockup)!

The projects responce to this was when the drill was running the LED was lit (maybe mid-way) I adjusted the pots until the LED were very dim, then tripped the relay, LED lit with the tripping of the relay! (maybe midway).  So far its working!!!!!

Still have to try it on the real thing! Need to do some expermenting with a probe to attached to the piezo.

Still need to do the upgrade on the LED on page 76!

Spent most of the time trying to figure out the colors on resisters.