# Lux / light level

Does a lux sensor measure all light levels, or just ‘daylight’ levels?

I’ve tried various Google searches and ended up with all sorts of random pages that don’t actually answer the question.

I ask because the sensor for the automatic headlights on my car can tell if I’m driving in daylight, or in a well lit tunnel. Is it a different kind of sensor? Solar?

If lux does measure all light, rather than daylight, how are people using this for lightning automations? (because surely once the lights have been turned on they never go off again?)

Thanks!

Light levels - from any source of light. Just like the one in your smart phone.

I use it to know when to turn lights on (when there’s activity in the room, and it’s dark), or off (when the room is bright enough from other light).

It’s the last bit that confuses me…

If it’s measuring all light, surely the lights never go off, as it doesn’t know that there’s enough light from other sources?

Example…

• it’s daytime
• sun starts going down, light levels get low
• lux sensor reads level at X
• automation switches lights on
• lux sensor reads level at Y
• because the lights are on, level never goes back to X to switch off

Or am I looking at this all wrong?

I use philips motion sensors to get lux and control lights just like @Tinkerer

When it’s dark outside, and all lights are on inside, the lux level “only” goes up to about 10000. At noon, in clear sky, the lux level is about 22000 in my living room. I have an automation that switches off the lights if lux goes above 20000 or so.

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You get light levels out of the sensor, it’s not a “light/no light” situation.

So, for me, the light levels get low about 20 lux (based on my sensor and the location of it). That’s the point that I start turning lights on. Those lights bring the room up to about 20 lux - if I turn on the main lights it brings the room to about 70 lux.

As the sun rises, the room gets brighter until it passes the “lights off” trigger values, and the lights turn off.

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The lights will surely go off, because the light from the sun is much more dominant than your light bulbs. You could in theory, though, have light bulbs that give so much light that they would never switch off, just like you say.

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Here you can see a chart of light levels in my living room. I live quite a bit north so the sun sets at about 1600. After that, the lights come on. During the night, the level is zero. It peaks at about noon. Maybe that can help with the confusion

Yeah, I get it now

Thanks all

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Can’t believe I didn’t realise you could use a motion sensor to measure light level, was literally just thinking there must be a better way to control my sunset lights than time when I saw this

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Depends on the sensor, but both my motion sensors have light sensors too

Some sensors are better for different light levels. For example, a TEMT6000 sensor is only good for indoor light levels. https://www.sparkfun.com/products/8688.

Just read I can attach a GY-302 to one of my Sonoffs for peanuts so that looks like a winner. Probably hide it inside Mr Potato Head

Did you get it working?
I want to connect sensor to sonoff basic to measure lux

I’m trying to do this with a Hue sensor but can figure it out

@Matt112 , this is what I ended up with…