You must’ve seen the funky lights at the Disco or music festivals that are synchronized to the music being played. Every beat flashes a random colour of light or simply switches the spotlights on and off. In today’s DIY project, we are gonna teach you how to do exactly that but in your own room, Music Reactive Using light system.

Things you’ll need:

  • A LED strip of desired length and colour
  • Any NPN transistor (We Used 2N3904 NPN)
  • Some wires for connections
  • Power supply for the LED
  • A bass unit speaker (optional)
  • A microphone (optional)
  • A Multimeter (optional)
  • Soldering iron or Glue gun

Now to get started, First to clarify what we are building in the first place, is essentially, an amplifier. Basically, we are going to take an input signal from our speaker (or mic if you prefer that) and we are going to amplify that signal and apply it to our LED strip. Sounds simple right, it actually is.

Music Reactive Using Light in Easy steps

Step 1: Getting the Input:

For starters, we need to open the bass compartment (sub-woofer) of our speakers (that is the big speaker that goes bumm bumm). Now we need to unscrew the driver from the box of the sub-woofer. As shown in the image below, we see the driver itself is connected to the internal circuitry with just two wires.

You can find the Driver of your speaker below or on its sides
The Driver is powered by these two wires connected to it
(We Use it as our Input Source)

All we need to do here is to attach extensions from these two wires. as shown in the image below. You could solder them as I did or simply wrap around if you are just testing this.

Speaker Driver with connected wires

Now we can close the sub-woofer box and we keep the two wires outside the box. These Two wires are our input source.

Step 2: Making the Amplifier:

Now I hope that you were able to acquire the NPN transistor easier than me. I had to desolder it from a power supply that was defective.

Parts of a Transistor

Now to make the Amplifier for our circuit we need the Transistor to be attached to the input source and the LED strip in a way that is described in this circuit below.

A Very basic circuit diagram.

Pretty hard to understand the circuit schematics right?… If you are a hardware engineer or at least have the know-how of reading the circuit drawn above then I assume you could figure out the rest from here on.

But for those of us (like me) who think that this circuit diagram looks more like a doodle, I have attached the photos of the step by step assembly of the circuit.

Now, to start making the Circuit of a basic Audio Amplifier and use it as a Music reactive light controller, we need to plug the Input source wires(The Two wires from the sub-woofer) into the Emitter and Collector parts of our transistor, As shown below.

Here you might need to use trial and error if you can’t find the datasheet of your transistor, but most manufacturers will have posted their devices data sheet on the web. To find your transistors datasheet simply search the web for the serial number written on it (For Example: searching for “2N3904 datasheet” leads to its datasheet

Now from there, you can figure out the Base, Collector and Emitter parts of your own transistor. Here we solder the input signal wires of the sub-woofer to the BASE and the EMITTER parts after that is done, we need to work on the LED lights.

The first thing you should note on your LEDs is the Polarity. LEDs are essentially diodes and they work only when current flows in one specific direction. Usually, they are labelled but if you are not sure then you can find their polarity by using a multi-meter or a single AA battery.

Making Reactive Using light (LED light) …

Next up, you need to find an ample power supply that your LEDs are rated for, I have used a 12volt power adapter that came with the LED strip that I used. After figuring out the polarity of the LEDs most of the work is done, just connect one wire to the COLLECTOR of your transistor and attach it to the Negative end of your LED strip and the Positive terminal of your LED strip goes to the power source’s Positive terminal (which can be found with a multi-meter or simple trial and error with a single sacrificial LED)

Music Reactive Using Light:
Here we connect the LED Lights to our circuit, Positive End to the Power adapter's positive terminal and the negative end of the LEDs to the Collector of the Transistor
Here we connect the LED Lights to our circuit, Positive End to the Power adapter’s positive terminal and the negative end of the LEDs to the Collector of the Transistor

Now the circuit is almost complete except for the fact that the negative terminal of the power supply is not plugged to anything right? So let’s fix that and connect it to the input signal wire that we connected to the Emitter of the transistor as shown below


Now the circuit is complete and you can stick your LED strip to the wall as I did in the video above. I had to cut and re-solder some parts of the LED strip on the wall itself so be ready to do that if your design is going to be complex.

Now simply fire it up and the LEDs should blink as the bass is activated.

Permanent light / Night light Hack

Now this project can be extended into a night light as well. So when you get bored of the flickering of the light to the music and you feel sleepy you can simply flick a switch on the circuit and turn it into a night light.

To do that all you need is a SWITCH and two pieces of wires.

Simply, attach the two wires to the corner terminals of the switch. And solder these two wires to the COLLECTOR and the EMITTER of your transistor. After this, every time this switch is activated our entire Amplifier is by-passed and the current flows through the LED strip as it normally would. Even the Bass/Input Signal will not affect the strip once you turn it on.

Making a box for circuitry

Now we cannot simply let all these messy wires be like they are, what we need is a housing unit for this circuitry. To make this we will use milk plastic (a.k.a. casein) which can be made easily at home with readily available ingredients. Read up “INSERT CASEIN MAKING ARTICLE LINK HERE” to make endless amounts of biodegradable plastics for your own DIY projects. Hope you loved reading and created your own Reactive Using light.

also, check Top 10 Inventors Killed By Their Own Inventions


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