So I have found a few different sound detection circuits, but they usually integrate a mic and an amplifier circuit. I want to make a circuit that takes in headphone or line level audio via 3.5mm jack that will close a relay when a sound is coming through the input. From what I understand headphone and line level audio has more power than mic level audio signals. The audio signal does not have to continue on to a speaker or anything after going through the circuit, and doesn't have to sound like anything in particular (can just be a series of tones and quiet periods)
controller with 3.5mm stereo audio input jack.
Loud sound on left channel input -> close relay1
Loud sound on right channel input-> close relay2
left and right channels should be independent of each other
when a sound closes a relay, the relay should stay closed for the duration of the sound
I have seen on instructable and youtube people just wiring led and transistors to cut off headphone cables or to speakers to make sound reactive lights. But when someone takes the time to draw up a scematics it usually has caps and other components, so the instructables and youtube methods seem more like a hack than proper circuit design. That being said I would like to keep this as simple and as cheap as possible.
I am an absolute novice at circuit design and building. Any help provided would be appreicated.
The simplest circuit would
The simplest circuit would require a mic and an opamp. With this circuit, you would need a minium of a around 5 resistors and 1 capacitor for gain and high/low band filtering. For right and left, you would need to set up two of these(most opamps come in pairs so you’re in luck)setups as well as a paif of mics for R/L seperation. The output on the opamp can be used in an adc channel to get the level input for each discreet channel. I’m not quite sure what you mean by headpohne or line level though…those to my understanding would require a power amplifier like a lm741 I think. Currently I use an lm358 opamp which you should be able to find all kinds of resources for. I recently built the setup so I could start to record outside ambient sound levels as it’s part of my environment station(formally weather station).
The ususal setup is as follows I believe.
[Mic]–>(low/high filters)–>[opamp]–>[power amp]–{low power speaker or headphones}
The point after the opamp prior to the power amp you could use as an ADC signal output to your uProc. I currently have the above setup connected to a picaxe 08m for testing.
You may also want to look into a schmiddt(sp) trigger as well for your setup as this would negate the need for using an adc channel. This setup would then send a high signal when a specific level was reached and go back to a low signal when the lower level is reached. I would suggest doing a search on your favorite search engine for this info.
the two simple schematics
the two simple schematics that I have been looking at
sound detecting circuit (looks like goes throguh comparison before the amp stage?)
vu meter without an IC (I don’t want to build a VU meter, but this is a good reference, say I wanted to trigger my circuit with the 3rd or fourth LED level of volume, also I hope to have a 3 or 5 v circuit, not sure how to modify for that)
both mention a mic and an amplification stage. I will have a pre amplified signal coming in from a mp3 player audio out port (wired to my circuit, not through a microphone) , and I was unsure how to account for the signal already being amplified
AHhh…okay…so your last
AHhh…okay…so your last line was the missing piece, I was not quite clear about what you were looking to get the signal from.
So what are you looking to feed this signal into? Are you looking to feed it into a proc for processing or are you just looking for a circuit that at a specific level will trigger something.
If it’s just a circuit, then something like this might help.
With a proc you’d want to get the two signal lines (l/r) and use those on adc input lines with ground shared. You may need to use some resisters to lower the current, or possibly use an opto isolator(not sure if this is really necessary though). You may also need to do so low/high band filtering as well, but that you’d have to look up as well as I’m not familiar with audio signals and how to get what I need from them just yet…still learning about this stuff at the moment.
I plan using the audio to
I plan using the audio to trigger a camera’s remote lines through optoisolators.Each time a tone is heard the shutter is fired, if a long tone is heard the shutter button is held down.
So basically I want 2 seperate digital (on/off) signals from the left and right audio channels. Hopefully would not need all the high and low pass filters since I will be custom generating the control track on a computer to be played back rather than using a microphone to capture live audio.
I was pointed at this tone detecting circuit, but thought there was a simpler way that relied on sound amplitude rather that a specific frequency.
