A wearable sound-to-light display, without a microprocessor - the Musicator Junior.

Smaller than the 9-volt battery that powers it, the Musicator Jr. displays the sound it 'hears' (through the Electret Microphone) as fluctuating light bars.

Small enough to fit in your shirt pocket, it can also be placed on a flat surface to monitor the sound levels around it.

An alkaline battery will easily power it 20 or more hours.

Step 1 The parts needed

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The 'brains' of this project is a LM358 general-purpose op-amp which costs under 30-cents. The first half of the circuit is an amplifier which boosts the 500-micro-volts from an electret mic to about 1-volt. This level is generally called 'Line-level' and can be used to drive our LEDs, an audio amp, or even the input pins of an Arduino processor.

The second half of the op-amp is used as a voltage-to-current converter, which limits the brightness of the LEDs to 10mA or less.

The complete list of parts is below:

LEDs. Any combination can be used, as long as their total forward voltages is less then 8. For example, you can have up to 4 amber LEDs with 1.8v Vf.

Electret microphone - I got mine on eBay for under 25-cent
LM358 - Op-amp (8-pin DIP). Also available on eBay.
2N4401 - NPN general transistor (other audio NPN-types will probably work as well)
10k resistor x 5
2.2k resistor x 1
470k resistor x 1 (Can also be 330k as labeled in the circuit)
100-ohm resistor x 1
1uF capacitor
0.1uF capacitor
9-volt battery and connector
Perf-board and mounting parts.

Total cost: $3 or less.

Comments

[AronC0816]

I have to agree with the two people above me. I can somewhat read schematics but this one confuses me. It would have made more sense if the rectangular shape of the op-amp was included and the interior circuits were shown inside that box. Then you could show each of the eight pins and what they should connect to. I tried to wire this up but it took me over an hour and it doesn't work. So apparently i did something wrong.

[thealeks]

would it be hard to use 6 mics that individually trigger 6 LED's?

thanks

[qs]

Nor too certain what you aim to do here - you could easily drive 6 LEDs using just the 1 mic and circuit here - why complicate things?

[thealeks]

i want to set up a small light show for my guitar, and i want each mic to be activated by a single string, so when i play, a light will light up for each string thats played

[qs]

I think you will find that, in real life, this setup will not be able to distinguish between the strings. one mic will pretty much 'hear' the same thing as its neighbor. It MAY work if you have an electric guitar and can extract the signals from each separate pickup before it goes into the pre-amp stage.

[thealeks]

i was hopin i could lower the sensitivity, maybe by giving the mics less power, and putting the mics right up to the strings, so they only pic up their designated string. im still learning so i dont know much about this stuff, so i dont know if that will work or not

[qs]

The only way to find out is to build one and see if it can be mounted to exclude sounds from other strings.

An alternate approach is to use the approach used in this circuit which splits the input into 3 distinct (low, med & high) frequency channels to indicate the pitch, rather than the string played.

[thealeks]

i thought about that, but then the lights wont sync up with the strings, but the ideas not out.

last question, how would i change the sensitivity of the mic?

thanks for all your help, by the way, i appreciate it

[qs]

The 470k resistor named "Level" controls sensitivity - the lower its value, the lower the gain. it can also be a 500k adjustable resistor so you can play with the setting that works for you.

[thealeks]

ok awesome. thanks for your help. ill let you know how it turns out!

[phevtron]

how sensitive is it to sounds?

[qs]

With these electret mikes, it will work with low-power speakers played at regular volume. The sensitivity can also be adjusted to be about 10 times higher, but background noise will then become a problem.

As I mentioned, any sound you can hear clearly, it will display.

[phevtron]

thank you for replying :D you just offered a teen an amusing yet attractive decorative idea :P

[musick_08]

instead of a microphone, could you put on a 3.5mm jack so the lights flash to a music source?

[qs]

Check out my other circuit which uses only a handful of parts and takes the output from an Earphone plug to flash an LED. It was designed to use a USB supply, but any 4.5-6 volt supply will also work.

Circuits that only use a single transistor suffer from 2 major problems: they do not work unless the volume is cranked way up, and they distort and may even damage the sound source.

[musick_08]

I think this would work. i wanted a small circuit that could be used with a small battery source if needed. thanks

[The Insignificant User]

Try checking out this one: http://www.instructables.com/id/Music-LED-Light-Box/
I honestly think the circuitry on this one looks a bit simpler, but it should work for what you are thinking of.

[musick_08]

i've used the circuit for that on other projects, but i want one that can use a battery source for portability

[elijah_rippington]

i have built that circuit to run off a 9 volt battery by placing the LEDs in parallel, so its entirely portable.

[The Insignificant User]

Oh, I see. Well, I can't say that it would work for certain, but I've run several LED's off of 2 AA batteries with the proper resistor. I haven't used the transistor that was featured in that project before, but it shouldn't cause too much impedence, I think.

[sayray]

HI!! I am looking to create some inner light effects for a runway/hair show avant garde style... as in light would be glowing/flashing from inside the hair sculptures. Do you think something like this would work for it? Would it be bright enough for a dimly lit/ or dark stage? Could it be adjusted for more lights or brighter lights? Possibly flashing lights but w/out the music respose?? I am looking for a definate flashing/ good deal of light streaming out, not tiny rice lighting. What do you think?? Any help would me so so appreciated!!

[anarky2k]

ive made it....but my leds flash very dimmly and they have to be very close to the music source....ive gone over it and the only thing i have different is the transistor, i used a 2n2222a cause i couldnt find the other one.....could anytbody help me xS

[qs]

The PN2222 (the 2N2222 has a metal case) should be OK for 9-volts and the 3 LEDs used here but do not increase the voltage or current. Your problem may have something to do with the electret mic - read some of the responses below for fixes for dim light. They will probably answer your question. Some pictures and description of your build may help isolate the cause too!

[anarky2k]

jajaja thanks, ur right, the microphon didnt work, as soon as i put another one in it worked......noow i have a different issue....the leds dont turn off completly, they flicker alittle when theres no sound...any advice?

[qs]

First make sure you are not picking up noise from electrical equipment around you - or even hum from wall plugs (try a .1uF cap across the mic). If that doesn't fix it, you can lower the value of the 'level' resistor from 470k down to 330k. This reduces the sensitivity of the mic.

[mayur.phadte]

Thank You for dat humble help
I checked the wire at R3 as well as the wire no. 19(I didnt quite get you when u said R3 + wire 19) the leds go off when I remove it
I checked the wire no. 24 as well

[qs]

Then remove the (+) input to the second IC (pin 5 and #18 in the enlarged diagram below) If the light stays on - there is a problem with that part of the circuit - defective IC and/or wiring error.

Oh, and if you are running from a wall plug - it may be putting out too much noise - try with a 9v battery!

[mayur.phadte]

I removed the cap all together (100 nf)
removed one pin
removed the other
interchanged postion
LEDs are still on

[mayur.phadte]

I have dat cap
is it ok?
I think that's a polarized one
do I need to get a non polarized cap?

[qs]

Generally-speaking, caps with higher voltage ratings have higher internal resistance which cuts the signal available.

The cap in the pic is an electrolytic and it can be used. The side with the (-) stripe should face R3 in the circuit (below).

For the 'stuck on' condition, test from the LED end - start by removing the wire at R3 (19 in the circuit) - if the LEDs are still on, then your transistor is no good.

If it goes off then check wire 24 - this will force the LEDs on if it is not connected properly.

Let me know what happens and we can go from there.

[mayur.phadte]

Oh I hav a cap rated for exactly 50 volts..
so what is the recommended rating for this cap then?
even If I remove the cap the LEDs dont show any changes.they are still on no matter what i do.

[thebanano]

hello qs, nice work...
i building this musicator for over three times...
all the problem was the same....it doesn't seem sensitive to the sound
i'll have to stay closely the mic to the sound source, then the led response with a weak light...
i do changing the 10K Resistor with 10 to 47K as you said, but the result was still the same...i'm little bit confused, because i have no electronic bacground...perhaps you can help me...

ps :
1. i'm using 2uF replacing the 1uF, coz it's hard to find a non polarised cap with that value
2. i'm using 1/4 watt resistor
3. sorry for my english
4. thank you very much
5. :-)

[qs]

Is there a chance you could be using a starter moter condenser for the input cap? If your cap is rated for 50v or more, the ESR may be too high and that will cut the signal significantly. You do not need non-p capacitors, electrolytics and tantulums are OK - leave the (+) side facing the mic.

To get more response from the LEDs, change the "level" resistor from 470k to 560k. Do not go any higher than 680k since the noise will be quite high. If this does not improve things, then look for a problem with the parts, starting with the mic, IC and 2N4401.

[mayur.phadte]

This is what I got upto,but then when it is switched on it just lights up the 2 Red LEDs and isnt sensitive to Sound,Reverse Bias Doesn;t Work...!
Uploaded the Microphones too,I think there's a problem with my Mic..
Is Electret Mic something different?
Even tried connecting my mic reversed,,,still doesn't work/.!

[qs]

If the LEDs are lit as soon as they are connected, then likely it has to do with the transistor. One user had put in the wrong transistor (a PNP instead of NPN) and had that same problem. Also, you seem to have the LEDs connected in series - which will limit their function.

 

[mayur.phadte]

noticed one more thing..!
1)When I dont connect my mic(yeah! circuit minus mic)
2)When I short the two mic wires
The bulbs are still ON !
No flicker no change at all!

[mayur.phadte]

so u mean I need to connect LEDs in parallel???
so u mean 2N4401 is also available in a PNP variant?
so u mean...that's it.

[qs]

You are right, the LEDs should be in series.

Check the transistor's markings, if it says 2N4401 they you're OK, but sometimes the 2N4403 (a PNP) gets mixed in. Also make sure the C, B & E leads are properly placed - see the diagram below.

I'm also including a breadboard of the same project by another reader (thanks B Marsh!)- maybe it'll help. Note that he used a 3v supply and thus had the LEDs in parallel.

[qs]

My eyes must be going... In your picture, the wires on the left seem to go straight from + to - which will be a short circuit...

[mayur.phadte]

dont worry about that the leftmost wire(two wires going in) rising up is negative and next to it is positive(one wire going in)