1. Home
  2. Electronics Design
  3. LED Replacement for Halogen Lamp

LED Replacement for Halogen Lamp

I have a small collection of the tall halogen pole lamps with the dish shaped reflector which lights the ceiling. I'm actually fond of them and like the indirect light they provide. I don't like burning 500 watts of power though. So I thought I would try replacing it with LEDs.

A direct replacement for the halogen bulb gives of a fraction of the light, so I found some modules which are about 2 inches square using 50 watts with about the brightness of a 300 watt bulb. There are also 100 watt versions in the same package with the brightness of a 500 watt bulb, but I figured I'd start with a lower wattage to see how well I can get rid of the heat.

I decided to use some old frying pans as heat sinks. I started with the smaller 10 inch pan which could almost fit inside the lamp dish. But that would leave no room for the electronics so I left more space between the pan and the lamp dish. Just to get an idea of how well the heat sink works, I fired it up on the bench after sanding off the Teflon under the LED and applying a bit of heat sink grease.

warm. The frying pan... I mean heat sink it pretty warm to the touch,

right next to the LED. So clearly the LED isn't doing a great job of conducting the heat to the heat sink. The LED temp is reached pretty quickly, much faster than the heat sink warms up, so the limiting factor seems to be the LED and not the heat sink itself.

I am going to finish this, but I don't see how the 100 watt LED could possibly be used. Anyone used these before? The construction is a thin steel plate slightly large than the LEDs themselves, just large enough to have mounting holes. I can't tell how the LEDs are thermally connected to the plate. I suppose there is a circuit board inside which is not conducting the heat very well. I guess this may require building my own unit if I want the full light of a 500 watt halogen with a 100 watt LED.

I will say the 50 watt gives off lots of light. I wonder if it can be dimmed?

--

Rick C
Reply to
rickman
Loading thread data ...

bit

If you want it to last long you'll need to reduce the power. There's a lot of dodgy business with LED claims. If determined to push it you might get s ome mileage from fan cooling the top.

NT

Reply to
tabbypurr

I wanted to use a 100 watt LED with a 50 watt PSU, but it was cheaper to buy them together so I couldn't get that combo. I will try getting the

100 watt LED which will at least provide a lower current to each LED individually even if it doesn't lower the temperature. 
--

Rick C
Reply to
rickman

That's a cool idea. Where are you getting the LED lighting stuff? Any lynx to share?

--
Tim Wescott 
Control systems, embedded software and circuit design 
I'm looking for work!  See my website if you're interested 
http://www.wescottdesign.com
Reply to
Tim Wescott

Just eBay. Tons of vendors and looking a little while ago I see there is a new package for these modules which has much less exposed metal on top and no solder-able tabs that I can see. The listing I bought from isn't available anymore.

I watched a video about how dodgy these LED modules are. Poor matching of LEDs and many don't work at all. Mine has one LED that doesn't shine. Haven't tested at lower power levels to see if the LEDs are poorly matched. I guess these modules are made with the many LED dropouts that don't pass testing and are sold for pennies.

I wonder how you get a good module? I'd also like to get a dimmable supply.

--

Rick C
Reply to
rickman

I did a big search for efficient LEDs a while ago, and made retrofits for dual 48" fluorescent ceiling fixtures.

I replaced the 2 tubes with a single line of 20 1 W LEDs (350 mA at ~ 3 V each). I soldered these to a 2" wide piece of PC board material about

44" long. I used a commercial power supply from Digi-Key.

See

formatting link
for a picture, part numbers and other data.

This same setup could be used for the pole lamps, although putting the LEDs closer together makes the heat removal more difficult. 2000 Lumens is a HELL of a lot of light, don't look directly at the LEDs or you will be seeing spots for 20 minutes. I seriously doubt you need 100 W for efficient LEDs, this setup runs on a measured 21 W from the power mains.

Jon

Reply to
Jon Elson

Oh, the setup I mentioned in an earlier message has all the LEDs in series, so matching is not required. The string runs at 350 mA at about 58 V, and each LED produces about 100 lm.

The LED lighting power supplies I used are not dimmable, but for about $2 extra, you can get a dimmable version. They have ones that are PWM dimmable and others that are dimmable with a resistor or pot.

Jon

Reply to
Jon Elson

LEDs are about five or six times as efficient as incandescent lights. So to replace a 500 watt bulb a 100 watt LED lamp would be a good match. Perhaps you don't remember these torchiere lamps. But even with a 300 watt equivalent LED (what I'm calling the 50 watt unit) it runs too durn hot for the LED to last I think.

These things shine the light upward to the ceiling, not down at the stuff you want to see. Reflected light looks nice, but a lot is lost.

Maybe I'm doing this wrong. Maybe I should put in a number of lamps on the wall that shine upward, maybe each one a 20 watt LED which should work a bit better heat wise, or even a few 10 watters.

--

Rick C
Reply to
rickman

These lamps have multiple strings of 10 LEDs. I think the matching is both between strings to get equal voltage and within the strings to get equal brightness. The video I watched showed how at low currents some individual LEDs would turn on sooner than others and be much brighter. Not sure what was happening, but I expect these are made with reject LEDs.

Where did you get your PSU? The only dimmable PSUs I can find are an arm and a leg.

--

Rick C
Reply to
rickman

try banggood.com & similar. Expect 3rd world quality & safety.

NT

Reply to
tabbypurr

The best LEDs are pushing 150 lumens / watt. Halogen bulbs are around 25 lm / watt.

Yes. Very inefficient.

One of my to-do projects is to install a series string of power LEDs along the inside of a 10 ft piece of aluminum U-channel (for a shop light).

That spreads out the light and the heat. I haven't figured out an easy way to keep out the bugs, though. I don't have an easy source of 10ft x 1" window material in mind, or feel much like making a window-per-LED.

In the Department of Silly Walks department, I just added a silly heatsink to a ~$3.50 Walmart "Great Value" brand 12w 1,100 lumen LED. The low price intrigued me. Except for a possibly slightly smaller heatsink, it looked identical to another GV 1,100 lumen model advertising twice the life, selling for twice the price.

As purchased, horizontal, in free air, the bulb's case was running 84*C, a 62*C rise over ambient.

Last night I added a 0.04" aluminum 20"^2 (each side) disc, machined to fit, with impeller-style blades cut into the outer edge for better air-stirring.

Heat sink contact was poor, but it didn't seem to matter. Press-fit in place with ~30% metal-to-metal contact, temp rise was improved to 36*C over ambient. Epoxying in place with copper-loaded epoxy, I measure 37*C rise--no improvement.

Cheers, James Arthur

Reply to
dagmargoodboat

s.

0
0

an

he

e

on

a bit

?C

or

in

ch

ng

lot of dodgy business with LED claims. If determined to push it you might g et some mileage from fan cooling the top.

Why not rip the guts out of a few of those Great Value brand LED bulbs from Walmart, install those plus heatsink in your torchiere? 2,200 lumens worth of LEDs and power supplies, $7. Insulate the off-line works, natch.

Bonus: Get the dimmable types and you can use the built-in dimmer.

Cheers, James Arthur

Reply to
dagmargoodboat

Not a ridiculous idea. Maybe I'll buy one tomorrow to rip open and examine. But 2 klumen is not enough by at least 2.5x.

--

Rick C
Reply to
rickman

sh

m

EDs.

50
100

can

the

t

the

flon

ms a bit

h,

f
y

ctor

d

thin

gh

hich

ding

0

be

a lot of dodgy business with LED claims. If determined to push it you might get some mileage from fan cooling the top.

to

e

from

rth

You can use as many bulbs as you want.

The diffuser globe is glued with a bead of silicone seal. Wrench it off holding the bulb in two hands. Preheating the globe by running the bulb (or with a hairdryer) to soften it helps, if it's too difficult to manage by hand.

Underneath, the LED assembly is attached to the heatsink with two screws. Remove them and the LED assembly comes off easily.

The bulb tip conductor is press-fit, and can be pried out with a screwdriver.

Cheers, James Arthur

Reply to
dagmargoodboat

I'm not sure what bulb you found that puts out 2,200 lumens. I am not finding anything that bright and that cheap. I found a 100 watt equivalent with 1600 lumens. I would need at least five of those at $12 each. I'm also not sure how they would be mounted on a heat sink. Can the LED boards be flattened out to mount on a flat surface? Any idea what the dimensions would need to be? Looking at LED bulbs with Google shows many different internal configurations.

--

Rick C
Reply to
rickman

dish

hem

0

LEDs.

he

ng 50

o 100

t

I can

th the

But

l the

Teflon

eems a bit

uch,

of

tty

factor

uld

a thin

ough

which

ilding

100

n be

s a lot of dodgy business with LED claims. If determined to push it you mig ht get some mileage from fan cooling the top.

r to

the

s from

worth

f

ge

s.

Up-thread I wrote about heat-sinking a 1,100-lumen 12w Great Value bulb. The local Walmarts have them for $3.50, x2 = 2,200 lumens for $7.

They are not dimmable, however. Not on Walmart.com, AFAICT. The cheap one has a heavy, ribbed body, same appearance as this one--

formatting link

Walmart's 800-lumen bulbs may yield more lumens / $.

For example, 4x800=3,200 lumens @ $6.44:

formatting link

The dimmable versions are a little more expensive.

My local stores' prices are lower than Walmart.com's on several of these items. YMMV.

Cheers, James Arthur

Reply to
dagmargoodboat

Ok, I've seen 1100 lumen bulbs but I'd need 8 of them and I'm not sure that many would fit. In fact, I'm pretty sure they won't.

I would need 10 of the 800 lumen bulbs which is definitely too many. For $65 I can get a dimmable PSU for the 100 watt LED.

--

Rick C
Reply to
rickman

The LEDs are mounted on an aluminum-core disc PCB ~2" in diameter. The various Great Value bulb models just seem to mount more or fewer LEDs on the assembly.

Spreading those heat sources around your frying-pan heat sink avoids the need for a massively thick heat spreader. Also lets them run cooler, improving lifespan and efficiency.

That works, but you'll need a CPU cooler and a fan. Or a heatpipe. 100W/in^2. Water cooling is always nice.

Cheers, James Arthur

Reply to
dagmargoodboat

Lol! I could make a water project out of it and shine the light up through the tank. Maybe let it heat an aquarium.

--

Rick C
Reply to
rickman

These are $9.42 at the local Walmart, and only three in stock.

These are the same price, in my local store.

Reply to
Michael A. Terrell

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.