Flag Light

[Don42]

The American flag should be either lowered or illuminated at night.

Solar powered flag lights are readily available. I found one for $29.95 at Menard's. Unfortunately, they are quite feeble, seemingly providing about as much light as a birthday candle or an excited firefly. So I decided to make a light. Mine does not need to be solar powered. My flag pole is only about 20 feet from the cabin, so my flag light can be mounted on the cabin and powered from an outside outlet.



I used a CREE XP-G2 white LED . This LED produces about 254 lumens when fed with 700 mA of current. These are $3.99 each. I coupled it to a Carlco 10003 molded plastic TIR (total internal reflection) optic with a 12-degree beamwidth. These are $1.25 each. The lens is held in a Carlco 10734 20mm plastic lens holder for 23 cents. All of the foregoing are available from a number of sources. I used
LEDSupply - For All Your LED Project Needs!.

I machined the housing from 1" dia aluminum barstock. There is a cylindrical aluminum slug inside. The star-mounted LED mates up against the end of this slug with thermal grease. The slug fits snugly inside the housing with about .001" radial clearance, with thermal grease filling the gap. This provides intimate thermal contact between the LED and the housing so the entire housing can serve as a heat sink. The result is that when running a bit more than 2.25 watts (750 mA at about 3 volts) the case temperature is less than 120 deg F, a very comfortable temp for the LED. A rear cap is press-fit into the housing to seal it.

The lens fits snugly in the housing and is seated on the LED. It is held in place by the lens holder, which has little posts that seat into holes in the LED's star mount. All this is fixed in place axially by a nose collar that was machined to be a waterproof (.001" interference) press fit on the housing. There is a thin film of silicone between the collar and the lens and lens holder.

The leads come out thru a hole in the back cap which has been plugged and sealed with Silicone RTV, aka "elephant snot".

Simple electronics comprised of a cadmium sulfide cell, (surplus store or Digi-Key)), a cheap opamp (ST TS951LT, $0.89 from Digi-Key), a P-channel MOSFET and a few resistors comprise a series switch that turns the light on at late dusk when it is nearly dark and turns it off at early dawn. This lot is housed in a transparent pill bottle. The wire coming out the bottom is plugged with elephant snot. A plug was machined from delryn to fit the other end, with an O-ring seal. The hole in it that passes wire is also plugged and sealed with elephant snot.


I made an electronic current regulator for my light because I had all of the parts on hand, but a suitable power supply could also be just a 5-volt wallwart USB supply in series with a 2.7 ohm 2-watt resistor.

The light illuminates the flag very satisfactorily as can be seen in this photo.


This is not photoshopped; it's really what it looks like. It was very windy the night I took the photo so the flag is blurred, but you don't need a needle-sharp image to get a general impression of how it looks at night.

It is probably visible from across the lake 1.5 miles distant. Because the very tight 12-degree beam of light is aimed upwards at the flag atop an 17-foot pole, my neighbors can go skinny-dipping at night confident that they are quite invisible in stygian darkness though less than 100 feet from my flagpole.

[DIYer]

Thanks Don42! We've added your Flag Light to our Lighting category,
as well as to your builder page: Don42's Homemade Tools. Your receipt:

Flag Light by Don42

tags: light, LED, electronics

[Paul Jones]

Don42,

Excellent project and details. Using your housing as a heatsink and coupling with thermal grease has given me some ideas for other uses. I am impress with the sunset to sunrise electronics you have housed in a transparent pill bottle. You may think this is simple but I think it sounds pretty advanced for many other applications (e.g., Holiday decoration lighting). Thanks for the posting.

By the way, the CREE products are all well made products. Three years ago I retrofitted more than 50 ceiling recessed lighting fixtures in our house to energy efficient CREE LEDs with wide bezels making a very clean and contemporary looking conversion. The best thing was the CREE LEDs worked with all the 20 year old style Lutron Maestro dimmers and did not have to replace a single dimmer.

Regards, Paul

[impala807]

Great stuff, would like to have a go at making this. Could you possibly post the circuit?

[mattthemuppet]

love it, particularly the light sensor. LED lights are so simple to make, especially if you have access to a lathe and/ or mill, although to be truthful I've made a ton of different lights (my whole garage/ shop is lit with them) just with hand tools.

[LEDmeister]

Don42 this is a great post. I use LEDSupply often as well and they actually have a kit that they sell where you can select your LED and optic to be put within a 1" billeted housing. Here is their LED kit that you can select a Cree XP-G2 or any of their other high power LEDs along with the optic of your choice. With this, all you would need is a power supply or battery source and a driver with a constant current of 700mA like this compact driver choice.

Hope this helps those that are interested in a light like this. Love the use though and how well it did at lighting up the flag!