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I have been looking for an ambient light sensor to use with other IoT smart home devices. In my opinion this would be a commonly requested device for controlling internal lighting. For example if you had smart lighting, you may want to turn the lights off if the sun is shining brightly or turn the lights on if it's cloudy. Weather services could help, but ambient light at the location would be far more reliable.

Bonus points for hubless design (i.e. Wi-Fi and not ZWave/ZigBee) and integration with IFTTT, etc is also key.

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    Why are you looking for outdoor sensors to control indoor lighting? If you want perfect light inside, you should measure the light inside, not outside. – Helmar Feb 2 '17 at 20:37
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    Are you seeking an off-the-shelf product or you want to build one? – Bence Kaulics Feb 2 '17 at 20:53
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    @BenceKaulics Off the shelf would be preferred. Weatherproofing a raspberry pi zero doesn't sound like much fun. – ngless Feb 3 '17 at 22:14
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    @Helmar If you're measuring indoor light to determine whether or not you need to turn the lights on, you would have to have a mechanism to prevent feedback which would complicate the system. I'm not saying it wouldn't be a better approach, but it would definitely be more complex. – ngless Feb 10 '17 at 14:10
  • That's a valid point one has to consider – Helmar Feb 10 '17 at 14:21
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You did specify that ideally you didn't want a hub, but I think you'll either have to compromise on that if you want IFTTT to be able to integrate with the sensor.

If you're open to a Z-Wave sensor, the Everspring ST815 seems relatively suitable:

The Z-Wave Wireless Illumination Sensor with LCD Screen from Everspring activates programs or devices automatically based on illumination settings chosen in advance by the user. This sensor has a backlit LCD that displays a timer, illumination, transmission status and battery status. It has a lux (measurement relating to amount of visible light present) detecting range from 0 (darkness) to 3000 and a countdown timer that is adjustable from one minute up to eight hours. The sensor has a 60dB (decibel) built-in beeping tone/alert and has a wall-mountable design for use indoors or outdoors. The Z-Wave Wireless Illumination Sensor can be enrolled into any Z-Wave network to begin communicating with other Z-Wave enabled devices. It has an operating range up to 100 feet and is powered by three 1.5V AA batteries.

So, this device seems suitable because:

  • it is rated for both indoor and outdoor use
  • it can detect from 0 - 3000 lux, so although it won't detect bright sunlight, it should be able to tell between overcast and sunny conditions
  • configurable lux settings so that you can reduce false positive detections.

The Vera Hub seems to have relatively good support for the sensor, so it's an option if you can't find any Wi-Fi sensors that meet your requirements. Alternatively, you could consider making a sensor yourself if you're open to that; if you do decide to go down that route, you're welcome to edit the question.

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My team have been developed sensor for ambient light level sensor working on smart building lighting project. Sensor is based on of-the-shelf sensor (Texas Instruments OPT3001) adjusted for our proprietary protocol (xFSB). Mentioned sensor was chosen between 3 other sensors - so according to ours tests this one has really good performances.

We used values for outdoor light level as well ad indoor in order to calculate light level and light temperature inside the building (offices).

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    This is interesting to know. Do you have a solution (e.g. hardware) that you can share in this answer, so that others can benefit? At the minute, this doesn't really contain an answer that other people could use. – Aurora0001 Sep 5 '17 at 9:28
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    Thank you for advise, there is sensor model and link now included in my answer. – Amit Vujic Sep 5 '17 at 10:40
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The best I've found, that checks all of the boxes listed in the question is...

A personal weather station such as this one would do the job. It appears that some of these would give you an output of watts / m^2 which could then be used to decide if you wanted lights on or off (or even an inversely proportional dimmer setting)

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You can use simple camera (e.g CCTV) to capture image and process this image to get light info. Without any sensor.

Calculate the sum of R+G+B for all pixels divided by 3 then by the total number of pixels

S=0;
For (i = 0 to n-1){
S=S + Ri+Gi+Bi
}
Level = S/(3*n)

This will give a level value between 0 (dark) and 255 (bright) A similar Javascript implementation is gen here: http://jsfiddle.net/s7Wx2/ Test the result on the right of that page.

more

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    Please elaborate a way to do this. Otherwise this is more of a comment. – Helmar Sep 30 '18 at 16:39

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