Weather Support

Everybody talks about the weather but how do you use it?

Because without weather information your automation solution knows nothing about your environmental conditions. Is it hot? cold? windy? rainy?

Here are three examples of how users work with weather data.

A user in Phoenix adjusts his thermostat set point based upon the outside temperature. When it's really hot he bumps up the cooling setpoint, when really cold he lowers the heating setpoint a bit. In this way he trades off a small bit of comfort to save a lot on energy costs.

Another user in the San Juan Islands in Washington State has retractable awnings that can get damaged in the big winds they sometimes get. When the average wind speed in the last 30 minutes gets too high, or any gust over his threshold happens, HCA energizes the relay which runs the motor and the awnings roll up.

The last example has been done by many people we hear from: If it's too windy, or too hot, or raining, the garden watering sprinklers don't run. After all why waste water?

So don't you need an expensive weather station?


HCA can acquire weather data in four different ways:

  1. If you have any Davis Instruments weather station that has a computer interface and works with the Davis WeatherLink software, HCA can read weather data files produced by the WeatherLink program.

  2. If you have any weather station supported by two weather programs, Weather Display or Virtual Weather Station, you can use these programs to interact with the weather station and have the programs periodically export current weather data to a file. HCA is then configured to periodically read the current data from that file.
    Working with files and not the station directly has two major advantages. First, many makes and models of weather stations are supported (see the long list of supported hardware for each program). Second, these programs are the ones working directly with the weather station. After all, HCA is a great automation program but it is really not in the weather business. In this way you can use one of the weather programs to create graphs, charts, forecasts - weather data is cool! - and still have HCA use that data in whatever way makes sense in your automation solution.

  3. Get data from the Weather Underground web site. This has the advantage that you can access any weather station - yours, your friends, or public stations. In addition to current sensor data - temperature, humidity, etc - you can also access forecasts and astronomical data. If you have a weather station that HCA doesn't directly support from one of the weather programs, you can link it to weather underground - most stations support this - and then get the data from weather underground.

  4. The final method is to get your weather data from the aviation weather reports. Airports all over the country take hourly weather observations. They give you an indication of temperature, humidity, wind speed, and rain. Isn't that too inaccurate? After all who lives right near an airport? Well, it's probably good enough if you don't need too much precision. If you are looking for an indication of "too hot", "too cold", "too windy", or "too rainy", then almost always weather data from a nearby airport will do.

If you would like more information about weather support check out the Weather Section of the HCA Appendixes within the Documentation section.

Davis Instruments

Davis Instruments

HCA supports Davis Instruments Weather Stations - both their current offerings and older models - that have computer interfaces and work with the Davis WeatherLink software. Why use a weather station? You can create programs whose actions are based upon either current weather conditions or historic weather conditions.

Without a doubt having your own weather station is a very cool thing. Collecting data over time gives you the ability to do local forecasting and see weather trends over time. And that's quite a lot of fun.

But wouldn't it be nice to do something else with your weather data? Like what? Well, how about turning on your sprinkler system only if it is not too windy and hasn't rained the night before? Or open a skylight if it gets too hot inside but keep it closed on cool rainy days? And for those of you in the cold climates, turn on pipe heaters if the average temperature in the last 24 hours is less than 40 degrees?

With HCA and a weather station all these are possible.

While HCA uses the weather station for those sorts of automation decisions, it also can:

  • Append to a log file the sensor data read every 'n' minutes.
  • Read a template file and produce a new file with weather data substituted for placeholders. One use of this is to make a HTML file that can be available from a web server.

More information on the Davis Instruments weather stations can be obtained from their website.

Support for weather stations is in HCA Plus flavor of HCA.

Current weather conditions at HCA Central.

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