Author Topic: 12VDC LED Lamps  (Read 11406 times)

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Johann

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Re: 12VDC LED Lamps
« Reply #30 on: January 04, 2016, 06:06:06 PM »
I bought 12 volt LED bulbs like that, but they had 7 watts.
5 pieces for $20 about 2 weeks ago.

Mary B

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Re: 12VDC LED Lamps
« Reply #31 on: January 04, 2016, 07:12:00 PM »
If you buy and use a constant current supply the life of those leds will be extended. Run them a bit below(20% or so) of max current. You lose very little output of light but they run cooler/last longer.

OperaHouse

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Re: 12VDC LED Lamps
« Reply #32 on: January 05, 2016, 12:27:35 AM »
LED are more efficient at lower power. From the data sheet of a 9W unit the lm/W = 155@175mA, 137@350mA, 120@500mA, 112@700mA.  That is 38% more efficient at low power or 13% more loss each time the current is increased about 200mA.


Bruce S

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Re: 12VDC LED Lamps
« Reply #33 on: January 05, 2016, 07:18:49 AM »
Way way back in 2013  8) during my short stint up in Ohio, GHURD and when Rich and I made the trek to Philippines in 2010 , it really was interesting to see (pun intended) how well the human eye adjusts to lower light levels.
On both we were able to take 20ma LEDs down to 15ma before there was any perceived differences.
When a home's only source of light is a 12V/7Ah battery that gets charged from a 10 or 17 watt Solar panel , the saving adds up.
The picture I posted up here of the 80y/o lady was one of those defining moments.
To this day a spec my LED lights at 15ma instead of pushing them too much.
Cassy's LED master class remains on this forum if you are so inclined to read up on it.

A kind word often goes unsaid BUT never goes unheard

OperaHouse

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Re: 12VDC LED Lamps
« Reply #34 on: January 05, 2016, 08:52:13 AM »
Interesting you should mention that.  I have had an interest in LED at ultra low power
levels.  I did a little development project years ago for an organization that worked
with farmers is southeast asia.  Workers needed to monitor field pumps all night. That
involved them having to walk a mile on a two foor wide levee that often had snakes and
alligators resting.  Solution had to be cheap and easy to install.  I used a 3W LED
series die that operated at about 90V and a capacitive input voltage doubler.  My lawnmower
was a test bed for this with a connection to the points.  Less than a mw was enough to
be seen at distance when pointed at you. Most line voltage LED lamps have an anti ghost
resistor that consumes about a quarter watt to keep lamps off from capacitive pickup.

DamonHD

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Re: 12VDC LED Lamps
« Reply #35 on: January 06, 2016, 12:35:17 AM »
I'm running an LED nightlight off milliwatts or possibly microwatts.  Lasts months at a time off 4xAA NiMH.

http://www.earth.org.uk/LED-homebrew-nightlight.html

Rgds

Damon

Bruce S

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Re: 12VDC LED Lamps
« Reply #36 on: January 08, 2016, 09:15:12 AM »
Damon;
I read through your posting on that Night Light. Very interesting. I may be incorrect, but, it seems the PV may not have been charging the batteries , along with a possible bad battery.
I'd be curious about the latest update.
I have also seen that low dim but still usable light output from NiCD/NiMH batteries (The fact that they'll work until dead, is why I like using them so much).

I'll get a pic of a light we're using as a night light and add it to this post.
Still simply amazing how well LEDs can light up a room, even the cheapo one that run off AAs !!
I still owe a pic of the charger similar to what OperHouse posted in a different post.

Cheers
Bruce


A kind word often goes unsaid BUT never goes unheard