Making Things Talk

228 MAKING THINGS TALK

If you’ve got a workshop to take care of,

you’ll appreciate this project. You’re going

to attach a volatile organic compound

(VOC) sensor to an XBee radio to sense

the concentration of organic solvents in

the air in your shop. All too often, when

you’re working in the shop by yourself,

you become insensitive to the fumes of

the chemicals you’re working with. This

project is an attempt to remedy that issue.

The sensor values are sent to two other radios: one is

attached to an XPort, which is connected to the Internet.

From there, a PHP script reads the data and stores it in a

web document. The other radio is attached to a cymbal-

playing toy monkey elsewhere in the house that makes

an unholy racket when the organic solvent levels in the

shop get high. That way, the rest of the family will know

immediately if your shop is toxic. If you don’t share my

love of monkeys, anything that can be switched on from

a transistor can be controlled by this circuit. Figure 7-4

shows the network for this project. And Figure 7-3 shows

the completed elements of the project.

Reporting Toxic Chemicals in the Shop

WARNING: This project is designed for demonstration

purposes only. The sensor circuit hasn’t been calibrated. It

won’t save your life; it’ll just make you a bit more aware of

the solvents in your environment. Don’t rely on this circuit

if you need an accurate measurement ...