June 2004, Issue 167

Wireless Monitoring System

PLEASURE TO DESIGN

This project was a pleasure to design. The result is a simple and viable solution with excellent overall features. I hope you acknowledge its technical merit, too!

The system is highly optimized, with only a few components on the transmitter and receiver boards. Therefore, the system is definitely cost-effective, particularly the trap unit. Because there are up to 20 traps per receiver, even a $0.05 saving grows to be a dollar for a complete system.

Before starting this design, I was skeptical (to say the least) about the possibility of writing true C code for an eight-pin processor with only 128 bytes of RAM. Now I’m glad that I tried it. The compiler does a wonderful job of optimizing every single bit, and I had no trouble porting portions of code that were originally written for larger processors.

In the race for a better mousetrap there is no shortage of competition. I hope to see this unit in production some day. In my opinion, the design suits series-production technologies because it is easy to manufacture and test, and it doesn’t require calibration.

Nevertheless, being modular by design and flash memory microcontroller-based, you can easily adapt the system and add new features. System variants can range from translation to languages other than English and integration in a home control system, to the use of different radio frequencies. For use in your home, you can replace the LCD with a few LEDs. Furthermore, you can use the same basic design for other tasks, like checking if all of your windows and doors are closed. But that’s another story.