Environmental Monitoring with Arduino

Make the Gadget

This gadget is one of the simplest environmental sensors you can make. All it does is connect an antenna to one of Arduino’s analog ports and output the results as numbers and sounds.

There are some things about this device and how it works that make more sense once you’ve actually created and used it. So we’ve included that information after the build.

Parts

1. Arduino
2. 8-ohm speaker
3. 4Char display
4. 1-megaOhm resistor
5. 3–5 feet of solid core wire
6. Battery pack
7. Red and black jumpers

The 8-Ohm Speaker

We’re going to be using a standard 8-ohm speaker as the output. This is probably the most common kind of hobby audio output, one of the most basic (and oldest) electronic devices.

Simply put, a speaker is an electromagnet connected to a membrane. Variations in an electric current cause the electromagnet to turn on and off. This moves the membrane back and forth, which moves air molecules back and forth, which causes what we call sound.

If the movement is done rapidly enough, and if the voltage signal can be precisely controlled, the speaker will emit sound we can recognize—like music, or a person talking.

Before we begin to build the gadget, let’s be sure the 8-ohm speaker works:

Step 1 Plug your 8-ohm speaker into Arduino, as shown in the breadboard view (Figure 4-1): the red wire into digital pin 8 and the black wire into GND.

Figure 4-1. The speaker’s red wire should be inserted ...