Abstract

Using the Piezo Crystal from a standard long necked lighter, you can wire it to an amplifier and headphone jack to create a homemade microphone.

 

Intro

Long neck lighters are a pretty common appliance in most households. They offer a way to start small fires without the risk of burning yourself. A simple clicking ignition button on the lighter requires a small amount of force to start a fire. But how does clicking a button result in a flame? The answer lies in the Piezo Crystal. A Piezo Crystal is essentially a crystal that has a special molecular structure, and it is a main component of any long necked lighter. The main property that results from this structure is that if you hit one of these crystals, you will generate electricity! The amount of electricity you generate depends on how hard you hit the crystal. So, what you’re actually doing when you click the button on a lighter, is pushing down and releasing a small spring with a hammer attached to it. This hammer hits the Piezo Crystal that lies within the lighter, which generates an electric spark at the tip of the lighter. While the button is being held, a flow of flammable gas is being directed to the tip of the lighter as well. Once the gas contacts the heat from the spark, it ignites, and your flame is lit!

Another way we utilize piezo crystals is in microphones. It might sound bizarre, but fundamentally the crystal in a lighter and a microphone serve the same purpose, generating electricity based on force. The sound waves in the air, although small, are in fact a force. A piezo crystal can detect this force and generate electricity directly proportional to the sound waves it’s being pushed by. This electricity can then be fed into a circuit where it’s amplified and then sent to a computer or a speaker.

 

So the question is, can we create a microphone out of a lighter?

 

Materials + methods

1x Long necked lighter

1x Amplifying circuit

1x Soldering Gun

1x Cheap headphones/earphones

1x Thin piece of cardboard

1x Tape

1x Audio recording device

1. Dismantle the lighter
2. Extract the Piezo Crystal component
3. Solder the Piezo Crystal wires to the amplifying circuit
4. Snip off the end of the cheap headphones, leaving some wire before the headphone plug
5. Strip off the end of the headphone wire
6. Connect the left and right channel wires together with the soldering gun
7. Solder the headphone wires to the amplifier
8. Tape the Piezo Crystal to the thin cardboard
9. Plug in the headphone jack to your audio device

 

Results

At first, the wiring was correct, but the experimenter didn’t produce any sound in his audio recording.  He thought this was because the crystal wasn’t detecting enough vibrations, so he taped the crystal to a thin piece of cardboard so that the crystal would collect the vibrations from the cardboard but still nothing. He figured out that the issue was there was a high ohm resistor within his audio device that was completely snuffing out any input from his microphone. The combat this, he added an amplifier to his microphone to make the signal louder, and after doing this his microphone worked. It picked up his voice but the result wasn’t the best quality and it was really noisy.

Discussion

These results demonstrate the properties of the crystal. The force applied to it is proportional to the electricity produced. If it wasn’t, then the microphone wouldn’t be able to produce a clear voice, it would just be random static. Another interesting property is that the crystal can be used as a speaker aswell. The same way you can deform the crystal to produce electricity, you can also feed the crystal electricity and it will deform the same way. Speakers work by vibrating or deforming some element in the same frequency as a given audio input, so the crystal is essentially acting as a speaker aswell.

Conclusion

The crystal in a long necked lighter is functionally the same component as a crystal in a microphone. With this component and enough modification you can successfully create a microphone from a lighter.

 

Bibliography:

https://www.youtube.com/watch?v=ZlVI7YJGHq0&ab_channel=ElectroBOOM

https://www.electroboom.com/?p=1156

https://www.youtube.com/watch?v=wcJXA8IqYl8&t=0s