LED Replacement for Halogen Lamp

rickman · 2016-07-25T00:42:16+00:00

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 ...

Jul 25, 2016 22 Replies

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whit3rd 9 years ago

Cree makes 90 lumens/watt to 140 lumens/watt units. If you want 5000 lumens total, that means (assuming you have high-efficiency power supplies) your input is in the 35W to 60W range.

And it means you need to dissipate up to 35W to 60W of waste heat; about the same as a hot i5 CPU, with a fan atop it. You probably are better off with 8 LEDs, drawing 7.5W each, on modest heatsinks without fans. Getting separate AC/DC converters for each LED is gonna be wasteful.

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dagmargoodboat 9 years ago

I wouldn't trust 'em. 18W in that small a package is just gonna run too hot, even if 1/3rd leaves as useful light.

The 12W $3.50 version runs @ 62*C rise.

I like the 9W 800 lumen Great Value bulbs enough to graft heat sinks on them to make 'em last. :-) I cut the bottom off beer cans, fan out the edges, and epoxy to the bulb.

|| .-------. .' '. / \ . . . - . / / | \ \ . . \ | / . . \ - / | |----| |----| | | / - \ | ' \ / | \ / . \ ' | ' ' - ' / \ . . . ' . ______ .' (not to scale)

Fold out the "tabs" you see in the center, epoxy to the bulb case.

Cut "petals" (not shown) around the rim. Put a little twist in each petal, to let air through & mix the flow. (The result looks like an impeller wheel.)

Easy to make if you've got a lathe, more work with tin-snips and a drill. One sink cools the bulb ~17oC, two sinks doubles that.

Cheers, James Arthur

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Michael A. Terrell 9 years ago

I put three of these in the ceiling fan light kit that I added a few weeks ago. It is over my computer desk, and it is on from the time I get up, until bed time. There is barely room for the bulbs, in this light kit so a heat sink wouldn't help.

The new light replaces a floor lamp that flickered sue to the moving blades. With most of the light aimed down, it is a lot less annoying.

I'll pick up another package, and replace the bulbs in the gate post lanterns. I started with some 1.5 W LED lamps there about seven or eight years ago. They were all I could find at the time. I upgraded to three W bulbs last year, but a little more light wouldn't hurt, at night.

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