An active speaker circuit
A speaker turns electricity into sound. It needs 2 parts, the physical speaker and a timing circuit to create frequency (because sound is a wave).
Speakers fall into 2 categories: passive and active.
Active speakers have a built in frequency circuit to handle their own sound generation & you just need to feed them power to start speaking.
Most active speakers are hardwired to only work at a set frequency, so they'll act as buzzers or beepers. When you buy an active speaker, make sure it's the frequency you want.
If you want to play music, you'll need to use a passive speaker.
Recommended part: C96093 Recommended part: C115184
Passive speakers don't have a timer in them and only make sound when you feed them a wave of power.
You can drive a passive speaker with a :timer circuit that you design, or a pre-built timing crystal.
Different frequencies create different sounds. If you want to check what your frequency will sound like, you can use an online frequency generator.
Today we're going to make a simple (passive) speaker circuit. It can play beeps and buzzes, but is probably not good enough to play complex audio like speech. You can chain a couple together to make a musical keyboard.
To see what it sounds like, click here:
- Annoying buzz
- Beeps
- Simple music
- VCC is where we add power
- GND links to ground
To create a frequency we need to turn on and off the power to the circuit. For the middle C sound sample, the circuit turned on and off 45,000 times a second (a little faster than a human can do it).
You can create your own :timer circuit combined with a speaker.
To change the volume of a speaker we can increase the power to it or add resistance to it. Speakers have a maximum volume before they blow out, so make sure to read the spec sheet!
Here is a simple circuit that uses a potentiometer to control the volume of a speaker.