Part III: Testing the speaker

To know beforehand if the coil would even work, you can measure the amount of resistance the coil has in ohms. The teachers put up a helpful chart that told the resistance of all kinds of material per winding. Our coil would have a resistance of around 3.6 ohms. The ideal resistance lays in between 4 and 8 ohms. That means we could expect our coil to work, but pretty quietly.

Finally, to test the coil, it needs to be connected to a phone, a battery and to the previously created amplifier. You can first connect the crocodile clips to both ends of the coil that you made. For the battery we use a voltage supply. Set the voltage to 5V and the current to 0,250 Ampere. Connect the black wire to the ground wire soldered to the motherboard. In our case this is the white wire. Connect the red wire of the voltage supply to the brown wire. Next, place the coil on top of a carton coffee cup. Let it rest so that the coil sits in the middle. Now connect the auxiliary cable to your phone and play music. Finally hover the magnets that were provided by the minor just above your coil. If you have done everything right, you should hear music.

To our surprise, we heard a very distorted sound. No music could really be identified from it. We tried to find out what happened, but couldn't wrap my head around it. Suddenly, Thijs made the remark that the sound was very bass heavy. I suddenly put two and two together: the music I had chosen was very bass heavy. The amplifier and/or the coil simply weren't powerful enough to translate that to good quality sound. I switched the music to Adele (because why not) and we could hear her beautiful voice quietly, but very clearly. So we knew we had a properly working coil.

An application for the speaker

A speaker like this could be sewn into a small night cap for small children. This could provide them with soft music to help them sleep at night. This could be beneficial for their own development and also beneficial for the parents, who don't need to wake up to help their children sleep..