Self adjusting lights that aim to keep a constant lux in a room? - Page 1
Forum section: electronics / projects

author: e100
author_rank: Frequent Contributor
timestamp: February 03, 2021, 05:07:44 pm
content: As far as I can tell these don't exist for home or office environments.Given that LEDs are now dominant are the any technical barriers to infinitely variable lights that can adjust themselves to suit the ambient illumination?

author: mvs
author_rank: Frequent Contributor
timestamp: February 03, 2021, 05:57:11 pm
content: Probably this problem is just a non-issue. Evolution has made the pupil of human eye adjustable, so there is no real need for constant illumination.On the technical side, correct measurements of amount of light and its distribution are more challenging that actual control of a light sources.

author: mjs
author_rank: Regular Contributor
timestamp: February 03, 2021, 06:39:48 pm
content: This is becoming standard functionality in office environments due to energy regulations - google for "daylight harvesting". The lifetime of LEDs can also be made longer by driving them at 80% in the beginning and increasing the power while they age.Here's one example of a sensor that can do both presence detection and closed loop light level control, there are many others:https://www.tridonic.com/com/en/download/data_sheets/basicDIM_Wireless_Sensor_5DP_en.pdf

author: e100
author_rank: Frequent Contributor
timestamp: February 03, 2021, 06:40:51 pm
content: Quote from: mvs on February 03, 2021, 05:57:11 pmI was thinking of the power saving during the dawn/dusk period. Depending on your location and time of year there's a hour or more where you don't need full power.

author: srb1954
author_rank: Super Contributor
timestamp: February 03, 2021, 09:45:58 pm
content: Quote from: e100 on February 03, 2021, 05:07:44 pmDimmable lighting is commonly used in modern office environments for minimising energy consumption when there is sufficient daylight coming through the windows.

author: penfold
author_rank: Frequent Contributor
timestamp: February 03, 2021, 11:03:02 pm
content: From the perspective of someone who's ended up doing a lot of detailed work at my 'office' desk as opposed to a separate lab space, I can vouch for the "adaptability of the eye" actually being a reason in favour of auto adjusting light. My reasoning being that for most of the day I have a good natural lighting and I can swap and change between normal computer work, pen and paper sketch-drafting or detailed inspection/soldering tasks without needing any additional task lighting until mid afternoon, my automatic response is to incrementally switch on task lights... but there's a bit of a 'lag' period where I'll have gone back and forth trying to re-read some IC marking before I make the decision I need more light.Power savings are pretty marginal for the task lamps, but has anyone made a task lamp which self adjusts based on the light reflected back from a surface, maybe using an imaging sensor to compensate for more or less reflective surfaces? Its really more of a comfort/consistency thing than energy saving, but hey... it would make for a fantastically investable IoT project... a lamp that makes sure no aspect of your work goes unseen.

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 04, 2021, 01:29:19 pm
content: Pretty easy to do by using a photodiode to detect how much light is bouncing back and then a slow control loop to adjust the brightness in a very gradual way.Quote from: penfold on February 03, 2021, 11:03:02 pmI use a flashlight for that, since the markings often read best with light from a specific direction. And a magnifier for small SMD parts.

author: penfold
author_rank: Frequent Contributor
timestamp: February 04, 2021, 04:18:45 pm
content: Quote from: NiHaoMike on February 04, 2021, 01:29:19 pmStrangely enough, I find that under well diffused natural daylight (northern hemisphere, south facing skylights, frequent cloud cover and mostly reflected off matt finished white walls) I don't have half the problem reading IC or resistor markings that I did in a "well-lit" lab. Not needed to use the flashlight trick since moving my office to the attic room.The point I was trying to make is that there is a time when the light has faded below the level needed for good detailed work but not so much that you notice during non-detailed. I see that as a good use case for auto-dimmed task lighting, working on the assumption its far more efficient to do that than light the room with a few hundred watts of flood lighting in the evening. I don't have a problem switching on any lamps as I need, but it would be nice to have an automatic seamless transition.I agree for simplicity of a photodiode, but perhaps something with the spatial resolution of an image sensor could discriminate between 'subject', 'background' and the contribution from multiple light sources to some benefit and maybe work in conjunction with ambient room lighting to reduce eye fatigue or some new condition one could invent to make the product sellable.

author: Yansi
author_rank: Super Contributor
timestamp: February 04, 2021, 04:22:40 pm
content: Quote from: e100 on February 03, 2021, 05:07:44 pmYou are wrong then, as I've already encountered such smart lighting in both buildings of my last two employers.//And mind you, in the canteen of my previous employer, there were dimmable fluorescent tubes, not even LEDs!//

author: Vovk_Z
author_rank: Super Contributor
timestamp: February 04, 2021, 07:43:34 pm
content: It seems to me that when a sun started to fade but it is still present a bit of natural light sum still gives much more light then room light. So it that intermediate time it is difficalt to see if light was switched or or off. That is why I dont see a reason to turn lights by 50-75 % - because it will give even less light, and will not be noticeably at all.I mean if we switch on a light - it is usually reasonably to turn it fully on. Unless you have very good illumination much larger then usual need (with an excess) - only then it is really need to be regulated.

author: Vovk_Z
author_rank: Super Contributor
timestamp: February 04, 2021, 07:49:36 pm
content: And the more dark it becames on a street - the less light we really need at home, because of eyes auto-adaptation.It is another reason why we dont need constant lux.(I'm not talking about industrial or laboratories, but there it can be possible the same an "opposite" situation).