Sunday, February 6, 2011

Hacking Osram NightLux


Ok, this blog had "DIY" included on reload, so here's a bit of it. (By "DIY" I mean hardwarish hacking, real-world directed mostly.)

For smarthoming purposes, I wanted to stick around my apartment LED motion-activated lights. Because it sucks to push the buttons of course. My requirements were: 1) LED; 2) motion-activated; 3) light-activated (works only at night); 4) thresholds adjustable; 5) battery-powered, so worked on power outages; 6) actually, accumulator-powered with builtin charger for technology to serve me, not me serving technology. Alas, as usual, it's "choose 2 of 3" thing. The best I could find were Osram's NightLux and SpyLux. The first one is floodlight-like, the second is flashlight-like. Well, they don't have builtin charger and - worst - don't have adjust knobs! The only control they have is off-10s delay-60s delay-always on.

And the light sensor threshold is actually pretty high - not facing a window, it starts to light just on cloudy weather. So, I went inside to see if knobs are there - no. What a shame for otherwise great product! But I found that light sensor actually looks into plastic covers, only slightly lighted by nearby PIR window. So, the hack for 1st NightLux was purely mechanical - I cut with my Dremel-like plastic inside which shadowed sensor. It helped. But I had to put it near the ceiling directly facing the bulb, because when it hanged on a fridge it still turned on couple of times until eco-bulb warmed up.

Well, I want to put the 2nd one in the hallway, where there's no direct window light at all. I could try drilling cover and exposing sensor, but have doubts such bad aesthetics would still help. So, I've set for real hardware hack this time, even if risking to brick it. The idea is to identify type of light sensor (photo-diod, photo-transistor, etc.) and resistor which passes current from it, then use old trick to either gently file it to increase resistance, or short-circuit with something to decrease.

I looked at the board more closely - it has small chip, marked M7616. Well, I am lucky, it's not custom one, datasheets are available.

(to be continued)

3 comments:

arnog said...

Hello,
I am interested in the same topic.
In the datasheet of the component, you can change the light sensitivity by adapting the R2 resistor according top the standard scheme.
I will try to find this resistor in the product tonight ;o)
Regards
Arno from France (electronic team manager for living and designer ;o)

pfalcon said...

Yes, typical schematic for light sensor is voltage divider with photo-resistor in one "leg". Bue the other would be an SMD resistor, so it will be harder to solder to/replace it.

So, a month ago, a year after publishing this post, I finally did what I wanted. I ended up shunting (connecting parallel to) photo-resistor with a variable resistor. Actually, having constant resistor + variable resistor is better, to make sure you never short-circuit the photo-resistor (I don't know what effect of that would be).

I used 100k const + 1M var., but based on my experience, I would suggest 500k + 500M, it would make easier to catch the exact threshold.

Sedo said...

Hi pfalcon,

I've just bought this NightLux product and also want to adjust the light sensitivity. Please do you have a photo or schema of what exactly you have done? I'm not very good at reading schemas but I can do "replace this with this" :)

Thank you very much

Sedo from Slovakia