This project prevents house hold water pipes from freezing during winter. It does this by momentarily releasing the water via a water valve when the outside temperature goes below zero degrees centigrade.

The system is divided into two sections: a remote end and a ground end. The remote system records temperature and transmits telemetry data via a 90Mhz FM link. The ground end receives this RF telemetry, demodulates it via an FM radio, and decodes and displays the data.

When the temperature goes below 1 degree, the ground system will activate the water valve for 1 second every 20 minutes. When the temperature goes below 4 degrees, it will activate the water valve every 15 minutes. The diagram below depicts a simple block diagram of the PAF system.

The ground system displays max and min temperature stats and how many times it has activated the pump on an LCD display. It also provides temperature information via a 2400 baud UART socket. This can be sent to a computer for logging. In the event that the FM Radio loses the signal, or the Ground Controller is not able to decode telemetry data (due to poor Signal to Noise ratio), then an alarm is sounded after 5 minutes of no telemetry signal. This will notify sleeping users that the system is not operating. Below are some pictures of the PAF system during it's testing phase:

The Ground System uses an Atmel AT89C2051 (Intel 8051 based) Microcontroller. The fireware was developed using LA51 assembler and the Burn project (Burn is an unmaintained projected authored by me and Terry Porter, circa 1999-2000).