Fan-cooled LED headlamp

[MattyF]

As I've discussed before, I wanted to make headlamps that can be quickly switched from yellow to red when the vehicle reverses, and to run off a car battery for many hours. So LEDs were the logical choice. But the final effect has to look like a gas mantle.

The headlamp reflectors are two feet wide and the LEDs have to shine towards the reflector, so a normal LED bulb is no good. I decided to have 90 yellow LEDs and 30 red LEDS. Here they are, wound on a copper heat sink (of course normally only one colour would be on at a time):

Here's a finished lamp with a Teflon tube and nylon mesh around it to diffuse the light:

Here are the copper and brass heatsinks:

But the 90 yellow LEDs got a bit hot after 20 minutes, so I put a 12v 1.4 watt computer fan on the back and that cooled the LEDs down to barely warm:

Here's the lamp without a diffuser. Looks a bit weird!

I put some 0.5mm Teflon around to diffuse the light.

Here's the headlamp from the front:

Yellow

and switched to red:

Red

Full steam ahead!

[Vir Campestris]

Don't want to worry you after all that work... but are you sure gas mantles are that yellow? ISTR them as surprisingly white - more so than a standard incandescent lamp. But it's many years since I saw one.

Andy

[polygonum]

Gas mantles often had a pronounced greenish-tinged light. (They were still using them on many Southern Region stations back when I was at school in Surrey.)

[John Williamson]

Slightly greener than incandescent lights, according to my digital camera. But it's a while since I used one, and ICBA filling up an Aladdin lamp to check. I last saw the standby gas lamp in the "useful junk" drawer in the house kitchen, along with a couple of spare mantles and gas cartridges.

[Dave Liquorice]

I wasn't going to say anything. B-)

Agreed, a nice white light with sometimes a hint of green. That yellow looks more like a wick based oil lamp light source than a gas (or paraffin) based mantle one.

About a year, the last power cut...

[chris French]

Yup, the butane/propane gas lanterns we use when camping give off a white light.

However, whilst Matty does say gas mantle, I wonder if that is what he means? If these are to replace the original lights on steam train surely they would have been paraffin or something, not gas anyway?

[MattyF]

The original lamp was very likely to be a wick based oil lamp, and I wanted a nice cheery yellow colour to match the existing small interior oil lamps. Besides a pure white light might look a bit much like LEDs, and I can't have that!

Some early steam engines had arc lights, but other drivers complained about being blinded by them. I hope to make a steam powered generator to keep the battery charged. There will be a lot of lights on the rest of the train, and they need power.