Sound Reactive Led




This instructable shows how to modify a pair of speakers to also pulse an LED (or multiple leds, you choice) to the beat.

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Step 1: Parts

For this project you shouldn't even need to buy anything

You need:

A pair of speakers (or one, whatever you want)

1 bright led (I chose red because I think it worked the best, plus it's my only bright LEDs on hand)

wires for permanent installation, or alligator clips for demonstration.

Step 2: Open the Speaker

Open up the speaker. Usually all the screws come out except one, so you just pull the case apart and it'll pop out.

Step 3: Locate the Speaker

see that big metal thing? That's a speaker. If any wires are coming off of it (like another speaker) that's easier to reach, then just use that. I think mine was hook up to a tweeter? I'm not an audio guy, so I'm not sure.

Step 4: Attach

attach either a wire or aligator clips to each connector. connect the other ends of the wire or aligator clip to your led. Even though it's an led, polarity doesn't matter for this application since it's ac. No resistor is needed either.

Step 5: Crank It

turn you speakers up and play music until the led is reactive. It starts being reactive at about 25%, but then (for me) it was best at half as loud as the speakers can go.

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    103 Discussions


    10 years ago on Introduction

    Does anyone know if this will work on my 5.1 surround sound as I'm concerned about the voltage on the main bass speaker.... On the back it says 240 volts (This will blow the LED right?) and 50hz even though i don't think hertz matter..

    7 replies

    Reply 10 years ago on Introduction

    yes it will. a regular led will need 3V, 3.5V max, and the absolute maximum commertial LED that i have seen was 24V


    Reply 10 years ago on Introduction

    wazzup333 do you have a meter? even a main bass speaker probably isn't getting 240v. the circuit driving the system probably just runs on 240. if you can find out what the speaker gets and then combine several led's in series it should work. for example if the speaker gets 12v then 4x 3v leds in series should work. I've never connected to speakers before so i'm not sure. also it seems like a speaker would be more of a current driven device then a voltage driven one. meaning it may step-down the 240v to a low voltage high current system. if that is the case be very careful be cause high amps can kill!!! to everyone who wants to try to contradict me. Yes its the amps that kill not voltage. people often build up tens of thousands of volts walking on carpet. but that is only pico-amps worth of charge. even 1.5v like in a AA battery can kill with enough current. it only takes about 50-60 mA across the heart to kill a person.


    Reply 9 years ago on Introduction

    Technically its a combination of the both volts and amps... .5 amps at 1.5volts isn't going to do you any harm, but that same .5 amps at say 10,000volts will kill you quite easily and quickly assuming it is able to be ran through your heart.


    Reply 9 years ago on Introduction

    Voltage makes it easier for the current to travel through the body, at 1.5 volts it would be impossible for 5 amps to kill you, it would probably take 1,000 or 10,000 amps at 1.5 volts to do the job but it could happen, though it is highly unlikely that you'll ever find 10,000 amps at 1.5 volts, you'll be most likely to find a high voltage low amp system


    Reply 7 years ago on Introduction

    Actually the voltage doesn't matter. 50mA (0.05A) across your heart will stop it from beating. Be it at 0.1V or 500,000V (although there's more fireworks at 500KV) it is possible to kill someone with a 1.5V battery, although not easy, it is possible.


    Reply 7 years ago on Introduction

    a 1.5v battery can't supply enough current to kill a person through their skin, or else it would happen all the time, (it may be possible if you insert electrodes into the veins and attach those to a AA battery it might be able to kill you). The problem is that the human body has an extremely high resistance (usually 500Kohm) Ohms law states V=IR or I =V/R at so 1.5/500K =0.000003 amps that can pass through your body from a 1.5v battery. Its way to small to kill you or even cause a slight tingling sensation which you start to feel at 0.001A


    10 years ago on Step 5

    B very careful. if u have a post amp from ur music player 2 ur speaker this is very bad. if u r outputting more than 5volts 2 ur speaker then u can blowup the led. just putting in a caution

    6 replies

    Actually, the day before yesterday me and my friend were hooking up some LED's and accidentally sent a straight 9v current through a 3v LED and after about 2 seconds it popped completely in half and launched across the room. It was pretty sweet haha :P

    It must have been High Current, just a nine volt battery will semi melt the inside, rendering it useless, if it was a higher current battery like a large lead acid battery, it'll blow up anything you connect it to


    Reply 8 years ago on Step 5

    sorry i'm new to electronics. could this danger be avoided by adding a resistor to the led?


    9 years ago on Introduction

    Hooking the LEDs up to the speaker directly shortens their life by a considerable amount because that sound current coming from the amp circuit/to the speakers is in AC. LEDs don't like AC current and it shortens their life. Instead you want to build a simple bridge rectifier out of 4 diodes (or you can buy a small pre-made one) to turn the current into DC so the LEDs will be happy and last longer. They aren't very hard to make. Wikipedia does a good job of explaining it and showing a simple schematic of the Diodes.


    9 years ago on Introduction

    I tried hooking up an LED to my speaker, but it wouldn't turn on until the volume was at it's maximum... I'de like to know how I can make this mod work without having to put the volume at it's maximum because it's WAY too loud :D

    1 reply