1-Wire Sensors

As noted elsewhere on this site, the solar, leaf wetness and Soil temperatures are monitored using dallas 1-wire sensors.

The 1-wire technology is an excellent way to monitor extra datapoints, and are compatible with the weather display application, so much so, that you can get an extra temp sensor working on WD within minutes of plugging it in. WD has 1-wire provision for multiple extra temp and Humidity sensors, as well as Baro, Solar and Soil/Leaf wetness. Lightning is also provided as a sensor input but I will come back to that later.

A control experiment to gauge the accuracy of a Davis Temp Sensor vs a 18S20PAR+ sensor running in parasitic mode.

Configured for the station are the following :

Solar Sensor

The Solar sensor is mounted in an IP waterproof box with an opaque cover, using a Ping-pong ball. The Sensor was purchased from Hobby Boards, and is very easy to configure in WD. It provides excellent granularity, showing deviation when clouds pass overhead.

Leaf Wetness

Added to the same IP box noted above, the Leaf wetness sensor is located on the outside of the IP box, with the moisture board inside. Again very easy to configure in WD, however there needs some prior testing and maths to ensure the moisture readings mean something.

Soil Temperature

The Simplest 1-wire sensor that can be made. The 18S20 Package (T09) is a standalone temperature sensor, which by soldering the 3 legs onto an old CAT5 cable makes a very capable soil temperature sensor. The temperature is taken from the surface, and 10cm down. This enables ground frost and air frost to be detected.

1-wire Adaptor

To add 1-wire to your station, you need an adaptor, which in this case is a USB adaptor plugged into the VMWare Host, and piped through to the guest server. The 1-wire Drivers are needed from the Maxim website, but do be careful as the windows 2000 ones are now no-longer available, and the win2003 drivers will not install if you are still on 2000. I have version 4.0 which supports 2000 if you need them.

Configuration

Backup your wdisplay.ini file, 1-wire can mash this if it all goes wrong !!

• Download 1-wire Drivers
• Install Drivers
• Plug in Adaptor, with a sensor connected
• Run onewireviewer.jar and check the sensor is visible. Make a note of the Serial Number of the sensor
• Close the jar application
• Start WD
• Go to Control Panel > COM Port and add the 1-wire connection details, and tick the I want to use a 1-wire device.
• Click on Dallas 1 wire Icon
• Click Save/Reset and check that the Serial number noted above is seen in the comms box
• Add the sensor to the relevent section in the 1 wire box, and CLICK Save/Reset to save the config.

And you should be recording data.

This assumes this is an additional sensor, to your established station as I did.

Sensor's in Test

Currently we have 2 sensors in test that will run on the 1-wire bus. These are a UV sensor and a Cloud Sensor.

The UV sensor uses a detector that provides a UV index output, which is picked up with the A/D on a DS2760

The Cloud Sensor does much the same as the UV sensor, but uses a Peltier sensor that has been used by many other amateur weather observers. This project uses the output of the Peltier, passing into a DS2760 A/D.

We are also working on a Solar FARS unit that uses a 1-wire interface to detect fan speed and battery charging levels. We acknowledge that if we are using a solar panel, why would we pass a wire to the 1-wire unit for these stats ... we could just run 2 more cables and have the fan bus powered .... where would be the fun in that ??