Weather Interface


Not sure where I first saw the Dallas One-Wire Weather Station but I believe it was from one of my ham radio buddies. I have had it almost two years and it was one of those projects that was on the back burner. This fall I decided to work on it and put it up in the air. I down loaded the code from Dallas Semiconductor and got it to work on the computer. I have been very happy with the way it works but did not want to have the computer up all of the time to look at what was happening outside. Note: Dallas Semiconductor announced on July 7, 2000 that they will no longer supply the 1-Wire Weather Sensor unit. A company out of Mexico picked up the design and you can order it from them. Tecnologia Aplicada http://www.aag.com.mx now supplies the 1-Wire Weather Instrument Kit V3.0. You can see http://www.aag.com.mx/weather.html for ordering information. They have kept the price very reasonable. I believe that the last one that I bought with shipping from Mexico was about to $110.00. Here is a picture of the Dallas Weather Station:

This is a picture of a 1-Wire Weather Station

When I was in Dayton OH for the yearly Dayton Hamvention (Amateur Radio Hamfest) I passed the Tucson Amateur Packet Radio booth. They had built a kit for the One-Wire Weather Station. So, I just had to buy one to play with. The kit's model number is the TAPR T-238. It is a general purpose Motorola HC68HC908GP32 micro controller-based board intended for use with the 1-wire bus and any device that needs a serial connection. Four pushbuttons switches and a Liquid Crystal Display provides the user interface. The initial application for the T-238 is a controller that accepts data from a Dallas Semiconductor weather sensor unit, processes it, and formats it for sending either directly to a Terminal Node Controller (TNC) for broadcasting in APRS format or to a computer for further processing and/or logging. There is nothing about this board that makes it solely a weather station. This is just a first application. Please check out their web site http://www.tapr.org/. You can also order the kit from their web site.

A list of available development tools for the MC68HC908 is available at http://mcu.motsps.com/dev_tools/index.html. Development tools are available from P&E Microsystems at http://www.pemicro.com/ics08/. Here is a picture of the finished board:

This is a picture of the Board

I was not sure how I was going to mount the board and display. There are several ways that you might do it. One is that on the board there is a header that will allow you to mount external setup switches. So you could build it into a box to make the weather station portable. I chose to make mine not so portable but where I could see it and set it on my radio bench. I used Plexiglas to make my box. I hate to buy a box when I could make one. Not that I am cheap but like to spend the money on the next project. Here is a picture of the finished product:

This is a picture of the Finished Interface

I still need to do some additional work on the weather station. I need to bring the station into the house and connect it to the work bench and calibrate the T-238 interface. Also the weather station is not accurate when it is out in the open with respect to the temperature sensor. The sensor is enclosed in the weather station and the Sun will heat up the enclosure causing it not to be accurate. Some of the station owners have built the temperature sensor in an external enclosure so that the surrounding air will circulate around the sensor making it more accurate. Also, some of the folks have interfaced a barometric sensor in the weather station. So I still have some work to do. I will update this project and tell you how we built the other two sensors so stay tune. Not sure when I will get this started. Well, hope you get some good information out of this project.