One of the specialist light level sensors we use is this twilight sensor which is mounted on the north side of our home, just under the roof line. This actually provides a binary output and not an actual light level.
We also use light dependent resistors to measure light level in our smart home. These are very cheap sensors that can be used with small processors like the Arduino or Raspberry Pi.
The main reason for installing light level sensors in our contextual smart home is that it is very useful to know if it is dark outside or in a room or zone. This can then be used to ensure intelligent control of lighting.
We have found that light level as a percentage is a much more useful measure than absolute lux levels, which are never properly calibrated or accurate anyway. Our light level sensors are also self-calibrating so that 0% represents the darkest level ever seen and 100% the brightest level ever seen.
The algorithm used to pre-process light level data from the dumb sensor is important and rate limit the number of updates being sent to our Home Control System is important. We have spent a lot of time optimising this, so that it is responsive but doesn't sent a huge number of updates. Typically we expect to see between 150 and 300 per day from each sensor.
Our @smartest_home occasionally tweets light level in various rooms/zones.
