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Contemporary Light

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rwm

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#1
I am starting on a small project. I need a lamp for my bedside table. Sure I could buy one but I have some requirements:
First it has to be cool and unique. I want a contemporary look.
I want a light that has two intensities. I would like a dim setting that is just bright enough to find a pen and write a note without bothering my eyes or waking my wife in the middle of the night. Then I would need a brighter intensity as well.
It has to have some kind of visible switch or landmark that I can find at night. I may use a dim LED or even a radioactive source.

I have started kicking around a few ideas. So far I am thinking about a cylindrical aluminum shape with a reflector that diffuses the light in a downward direction.

1519770496895.png

I made an interference fit plug for the bottom

1519770545983.png

I need to do some experimenting with LEDs and reflectors. I have no idea how this will come out but I hope you enjoy the trip. Please feel free to make suggestions as this takes shape. Anyone got experience with bright LEDs?

Robert
 
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RJSakowski

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#3
State of the art LED's are fairly efficient; more light, less heat. The last that I bought were COBB LED's, 30W and 50W.
https://www.ebay.com/itm/2726112108...il&pgrp=main:email&e=op&mchn=em&s=ci&mail=sys

The 30 watt put out somewhere round 3000 lumens, the equivalent of a 200w incandescent, and was quite comfortable with 60 sq. in. of heat sink.
These LED's run directly off 120 volt AC. Depending upon your need, you might want to look at the 20 watt COBB's. Less heat sink will be required and there is still a bright light. For home use, I use the warm white. The daylight LED's re too harsh. You will hgave to thermally couple the heat sink to the LED substrate, either with thermally conductive epoxy or heat sink compound. The cylinder that you have most likely would have more than enough surface area. I would use the exterior surface area in figuring the heat sink. If you put vent holse in the base of the fixture, you will also get a contribution from the inner surface. With the tall aspect ratio of your cylinder, you will most likely end up with a spot light.

PM me if you have any questions.
 

brino

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#4
State of the art LED's are fairly efficient; more light, less heat. The last that I bought were COBB LED's, 30W and 50W.
Thanks for the link Bob. I just ordered a number of those.
I am slowly upgrading my shop lighting as the fluorescent tubes or ballast die. I reuse the 4' sheet metal fixtures, rip out the guts and mount LEDs.
Those fixtures would be great heatsinks for multiples of the above LED modules.
-brino
 

RJSakowski

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#5
Thanks for the link Bob. I just ordered a number of those.
I am slowly upgrading my shop lighting as the fluorescent tubes or ballast die. I reuse the 4' sheet metal fixtures, rip out the guts and mount LEDs.
Those fixtures would be great heatsinks for multiples of the above LED modules.
-brino
Brino, keep in mind that steel is not a very good conductor of heat. Also, dissipating heat from a small source requires a significant cross sectional area. Thin sheet metal is not effective. If you mounted the LED modules on a piece of aluminum flat stock, say 1/8" or 1/4" thick, thermally bonded to your fixture, that should help.
 

mksj

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#6
If you go with a Halogen then you have a lot of heat to deal with and yes you would need a reflector and a glass lens. The housing can get very hot so you want a heat insulator or double wall with the reflector floating from the housing. . Alternatively you would not need a reflector for LED bulbs because the light output is directional, not radial like an incandescent bulb. You can also get LEDs with different beam angles and also dimmable. I use a lot of Philip's 12V MR16 LED bulbs in various lights, they are reliable, the color output (CRI) is neither too yellow or blue/white, and they come in various beam angles also some with glass lenses (see below). Makes for a low heat and compact light head. I also have retrofitted them to a lot of incandescent fixtures using a bi-pin socket with leads. You can get small LED power supplies, some with a dimmer or levels, also a touch sensor type that turn on and allow dimming by touch. A incandescent bulb would need a much larger power supply or transformer.
https://www.homedepot.com/p/Philips...immable-Glass-LED-Light-Bulb-470278/302187933
https://www.ebay.com/itm/LED-Touch-Dimmer-Switch-Sensor-Lamp-Accesories-DC-6-12V-XD-614/171436292474
https://www.ebay.com/itm/DC-5V-12V-...28-5050-LED-Strip-Light-Lighting/252658928834
LED.jpg
 

frugalguido

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#7
After going though a lot of the LED MR-16's because of poor color CRI and poor output compared to the 50watt halogens that I was using on the machines. I purchased some of these;
https://www.soraa.com/
IMHO, these are the best MR-16 LEDs on the market, much better than the Phillips, although they are more expensive at about $17+ each in single quantities . Replaced all the machine lamps with the Sorra's.
 

rwm

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#8
Wait! I appreciate the replies but I think you guys are thinking way too bright! I am thinking about using a 3-6 volt power supply like a wall wart with a single LED emitter. Something like this:

1519866540138.png

Or this:

1519866919827.png

The idea is not to light up the room but just provide soft light on the nightstand. I had a light like this before but it died.
I could also go to 12v and use and automotive LED.
Sorry I was not more clear about the wattage/lumen requirement.

Robert

EDIT:
Phillips and others make a MR16 12v spotlight that could work in this application. I will look at those also. The touch switch is a great idea. Thanks!
R
 
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mattthemuppet2

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#9
I have a lot of experience with LED lights :) You can always make a high power LED dimmer but you can't make a low power LED brighter! I'm pretty picky about lighting but two things I'm absolute on is colour temperature and colour rendering. For bedside use I would suggest around 2700 to 3000K max for colour temperature. that's a bit whiter than incandescent, but still warm. I would also suggest 85+ CRI (colour rendering index), so what you see in terms of colour is what the colour actually is.

I've tried some Cree 2700 and 3000K LEDs which work well, but the king of the heap for me are Nichia 219 LEDs. Anything below 5000K can be had in 92CRI minimum which is a really lovely light to use. I haven't used their 2700/3000K versions but I expect they would be similarly excellent.

For the most pleasant light, I would suggest having the LED fire up onto an inverted cone. LEDs are very bright point light sources, so getting the light spread out is a good idea. An opaque diffuser is another idea, although you lose some light in the process.

For different light levels you'll either have to get a constant current driver that would allow you to do so (I'm sure that there are plenty out there, just not used any myself for this application) or use a known voltage source and have a DPDT or rotary switch with different value resistors at each position. Calculate resistor value for the current you want to use and size them appropriately. For a high power LED 20mA will create a nice glow bright enough to see by but not so bright as to wake someone.

I've often thought about using clear acrylic rod for a light tube with an upwards firing LED in the base, have to get round to that at some point.
 

NortonDommi

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#10
The small LED's that you are looking at do not need heatsinks,it also looks like you have space to mount a few on a base and then mount in fixture.
There are small constant current drivers that are cheap and a switch block of some sort to switch on 1,2 or more is easy plus you can mix colour temperatures & colours! . Red at night to see your way around without triggering the wake signals is handy.
I've just replaced some 50 Watt Halogens in machine lights with 24V 30 Watt Cobbs in cool white and the difference in using the machines is *night & day*. Gotta love LED's.
 

rwm

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#11
I ordered this touch switch.

1519874650522.png

I am hoping to mount this in the base with the LED next to it or on top. Then I will just touch the metal housing to turn on/off. If this proves to be unreliable I will just go with a mini toggle.

Robert
 

RJSakowski

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#12
If you are looking at low wattage LED's, a constant current source isn't required. A simple dropping resistor or a dropping resistor in series with a variable resistor if you want a dimmable light will work well. You not have the efficiency of a constant current source but for a watt or two, it's not significant White LED's typically run on 3 to 3.5 volts. A 1 watt LED will draw about 300 ma. If a 6 volt D.C. wall wart were used, a dropping resistor of 8 - 10 ohms would limit the maximum current to around 300 ma. Adding a 100 ohm potentiometer in series would allow dimming to about 10% of maximum brightness. Total power drawn would be less than 2 watts.

State of the art LED's are running about 140 lumens/watt with 100+ lumens/watt common. As a benchmark a 60 watt incandescent bulb produces about 800 lumens.
 

rwm

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#13
I got the touch switch and set up a test circuit:

1520178980265.png

It works very well. Now I can just tap the light housing to turn it on or off. Thanks MKSJ! It has 3 brightness settings. I used a high intensity LED with a 1K resistor and it provides about the right intensity. I can always add LEDs if I want more brightness.

Robert
 
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rwm

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#14
I finally got around to finishing this project:

It has a very dim blue LED that is on all the time so you can find the light at night:
1521927212921.png

It uses a 3 stage touch switch and you can touch anywhere on the light to change the brightness:

1521927280317.png

That is the brightest setting. I ended using an LED from a Maglite. I think this will work great! I hope you like the look.

Robert
 
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