1-wire LUX sensors


Staff member
Is there such thing as a 1-wire LUX sensor? One of the things I liked about the Zanware controller is that it had onboard, and it would reflect the condition using a numeric value, which was really handy to deal with cloudy conditions etc. I would love to place one in each room.
I believe that there are 1-wire analog to digital converters. Therefore, you could use a cds photocell as a variable resistor or a solar cell as a variable voltage source. The digital output would range from 0-255 (assuming an 8 bit converter), so you would have to define the boundaries for "light" and "dark".
You should be able to do it with a DS2438 (the battery monitor) and maybe some others. Once upon a time, Dallas had planned to release a single sensor module with temperature, humidity, and light level (and maybe something else) - all based on the DS2438. The module they did release had temperature and humidity. They cancelled the updated version that included light.

But anyway, like WayneW describes, you could use one of these with a CdS cell (like you've used to monitor lights) and another resistor. This will provide a variable voltage that can be read by any A/D converter (the DS2438, an Ocelot, etc.).

There are boards available to do this. One example:
Solar Radiation board from www.hobby-boards.com
There are a couple variations (including temp and humidity) and they are also available as bare boards.
Not sure you want this in each room but this is what several users of Weather Display use as their solar sensor.


I personally use the $3 temp sensor in a jelly jar with Weather Display. It works perfectly. I have an event in HS that is triggered when the solar sensor reads 0%. This afternoon we had storms in the area and my lights came on around 4pm 30 minutes later they went out and then back on at dark.
How do you use a temp sensor to measure light? What is "Weather Display"? I have never heard of it. The Solar sensor looks nice, but just too expensive to deploy in each room. Thanks!
Did I read that right "a TEMPERATURE sensor". Do you have to compare outside temp against the jelly jar temp to determine solar output ? How do you use that temp to determine light level ?

Weather-Display is a weather software package that can connect to various weather stations. I use one wire. The temp sensor in a jar is like a green house and with the proper math and the ability to compare the sensor in the jar to the regular outdoor temp sensor WD calculates the solar light with a very high degree of accuracy. Have a look at http://weather.ruppworld.com/ for an example graph. It's mostly cloudy here today. Look at the lower right section of the main screen shot. There's also 2 and 3 day graphs further down.