Kitchen lighting

[Capt Slog]

I made this light some time ago, but I've only just around to using it.  Following the sucess and approval (by Mr.s Slog) of the LED spots, I thought it was time that ths was fitted.

The light is made of plastic conduit, around 1" wide, which has a snap-on lid.  I drilled through the lid to take 21 white LEDs, and they are wired in sets of 3 in series with a suitable resistor and then the 7 sets paralleled.  For the power supply I used an adjustable regulator chip, and this is set to 10volts.

At the time, I had no idea how the voltage would fluctuate from my batteries and windturbine arrangement, and this seemed a sensible solution to preserve the LEDs. The only other chips I knew about were the standard 12v variety, which of course need a lot more voltage to work correctly.  I've since found out about low drop-out regs, and will be using these for future fittings.

I've fitted the light strip to the bottom of the kitchen cabinets using a double sided adhesive strip and it has it's own light pull switch.  Although it obviously doesn't have the light output of the fluorescent strip you can see behind it, it's adequate, but best of all, it's running on home power.

[richhagen]

Looks nice, and it serves your purposes.  The 5mm LED's are not that good as area lights, and none I've seen are as efficient as flourescents, but for directional task lights like you have assembled, they are great.  Based on the counter items, I have to say . . . When life gives you lemons, make lemonade . . .  Seriously, it looks good.  Rich

[Capt Slog]

Since I made this, I've found that its possible to make the light from LEDs more diffuse by filing off their tops; making the domed bit flat and then repolishing.

.

[wooferhound]

That's a great idea

i was going to suggest that you put some kinda white tape over each LED

[Volvo farmer]

Do you have a measurement of the current that that fixture uses?

[ghurd]

Found a new use for those 80W?  Looks good!

Sand blast them.

Or get LEDs with a much wider viewing angle.

G-

[Capt Slog]

I honestly can't remember what it uses as a whole.  I know the LEDs are 55000mcd, because I've just looked back at my Ebay purchase from august last year. Similar ones on the same site use 20mA each and are 3.2volts typical.

I'd have stuck fairly close to this so using those figures it would be 20mA per series x 7, which comes to 140mA at the light but there will be some loss at the regulator too.  The regulator sees anything between 12 and 15v and loses more as heat as the voltage rises.

[richhagen]

I would think that in terms of lumens per watt, it is quite a bit less efficient than the flourescent.  The advantage for the LED fixture would be that it uses less overall power while putting the light where you need it.  The most efficient 5mm LED's I have seen are around 30 lumens per Watt but there may be some slightly more efficient ones now out there, whereas that flourescent is likely 2 or three times that.  The LED's are probably putting 90% of their output on that countertop whereas the flourescent is dispersing its light more evenly in all directions, putting maybe 33% or so on the countertop.   It is only now, the highest of efficient LED's that can rival LED's in overall visible light output efficiency, Cree and LumiLED's for example.  LED's have another advantages in there compactness, operation at lower temperatures, and there resistance to shock which I would think give them distinct advantages for certain applications.  Rich

[richhagen]

Whoops, this:  'It is only now, the highest of efficient LED's that can rival LED's in overall visible light output efficiency.'

That should be:  'It is only now, the highest of efficient LED's that can rival flourescent lighting in overall visible light output efficiency.'

[ghurd]

I'd like to kick in 1 cent about the efficiency, related to the needed light output. (I get emails)

At 140ma and 12.6V that's 1.75W.  If it makes enough light for the situation, great!

If the power available is under a couple hundred ma, or if the situation only needs a little light, LEDs still beat CFLs.

The smallest, common, good quality, 12VDC CFL is the 7W Solsum, pulling 660ma.  It's output is totally and completely dismal compared to the same 11W pulling about 900ma.  So poor, it is not worth trying to save the 250ma.  That might be why most stores don't carry the 7W version.

There are a few 12VDC CFLs at a lower wattage (1W, 3W and ?) but the light they make could be easily beat with good 5mm LEDs using less amps.  The tiny CFLs have to be seen in person to understand how bad they are.

I hope it's being driven at about 125ma for longer life than 140ma.

Plus the efficiency goes up!

G-

[richhagen]

Compact flourescents, at least the 15 Watt ones that I have been getting are only putting out about 60 Lumens per Watt.  A regular flourescent can put out at least 80 lumens per watt, high efficiency up to about a hundred.  I observe that if the need for light is only in one direction from the fixture, then since the LED's are generally already directional, that is an advantage as well. If you have the light you need where you need it at 1.75 Watts, why use 15 or 20 on a flourescent.  Rich

I found this chart which is a bit interesting:

http://www.mge.com/home/appliances/lighting/comparison.htm

I also found that Cree has tested LED's to 131 Lumens per Watt at least, and one can buy production LED's at 100+ lumens per Watt right now.  They would be too bright to look at directly as the 80 to 86 Lumen/Watt LED's I have are and they put out less light.  

http://www.fieldlines.com/story/2008/3/14/55046/0695

[elvin1949]

Rich

 Thanks for the link.

I need that for my lighting project.

later

Elvin