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Old 01-28-2013, 07:47 PM   #1
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LED Flashlights as an Exterior Illumination Source

LED Flashlights Adapted for use in RV's

ZEP has inspired me to investigate the possibility of using high quality LED flashlights to replace the tungsten filament bulbs with single element focusing LED flashlight systems. The replacements that make the most sense are the light over the door and the scare light to the right of the door. The Scare light does not do much other than blind you when you approach the trailer. For those of you that like to boon dock these LED lights over the best light output per watt of any other light source.

I am going to talk about three flashlight systems that I bought from a Chinese company called Dinodirect. It takes a long time to get stuff from them but the quality is good. They send stuff registered mail and it takes about a month and you will have to go to the post office to pick them up. If anyone finds a viable alternative to them feel free to post.

All three flashlights use 3 AAA batteries which produces about 3.5-4V at the LED when it is on. The first flashlight is the cheapest and the lowest output and beam quality of the other two but for about $6 each it is the best deal. It is 4.25 inches long and 1.25 inches in diameter at the widest part. The second flashlight is made into a headlamp and it probably the best one for messing around with and easy mounting. It is also shorter than the others that are tube shaped. The third flashlight is the best as far as light color, uniformity and overall output. It is about $11 each. This one is 1/2" longer than the cheaper one and the same 1.25" in diameter. All three of these will focus down to the point where they image the elements in the LED. The first two will focus wider than the third one but that could probably be changed with some sort of spacer. The first two slid in and out to focus and the third one you have to rotate. The slide mechanism is faster to use but since these will most likely be set and forget that is not an issue.

All three flashlights have three modes. The first is 100% power, the second is low power, and the 3rd is a strobe position. High power uses over .5A and low power uses about .15A. The modes are switched by cycling the power on and off within a few seconds. Normal operation is on-100% then off. If you want to change the mode you flip the switch on and off. There is a chip inside the element that does this mode switching and I don't think it also serves as a voltage regulator. I measured 3.5V at the element on the one I measured. The batteries put out 4.5V with no load. I did do some voltage comparisons at the battery and at the terminals of the LED. There are a couple 10ths of a volt loss on the high output setting. The voltage at the LED is about 2V on low power.
















Power consumption

Let's just assume 4V as the supply voltage for now for the purpose of determining power consumption. The cheapest flashlight uses .6A at 4V so that is P=IV which is 2.4W which is not much. The headlamp uses .43A at 4V so that is 1.72W. The third flashlight uses .72A at 4V so that is 2.88W. Lets just call all three of them 3W power draw on high for now. Now on low power all of these draw about .15A at 4V so that is .6W.

12V operation

Ok lets assume .65A for the two flashlights. We want to drop the voltage about 8V so we need a V=IR, R=V/I so that is 12V/.65A is 18.5 ohms which would be about a 20 ohms nominal resistance. You will need a power resistor rated at a few watts. The little brown striped jobs can't handle the current. Another way to do this, is to use a voltage regulator chip or daisy chain 3 or 4 of these in series. You are going to use more power across the resistor than the LED with the simpler resistor method. Whatever method you use, you need to verify voltage readings at the chip so you don't burn something up.

So what do they look like on the trailer at night? Just to get an idea what the illuminated area would look like, I taped the cheapest and most expensive flashlights to the top of the existing door light housing. The results were pretty darn good.

Here is the expensive one which does not have as wide of a beam as the cheap one. It looks pretty good.




Here is the cheaper one of the two.



Conclusion

The cheaper flashlight does fine. The illumination is good and you can see plenty well to find your key or read a newspaper. There is only light where you want it because the optics focus all the light in one direction and it is uniform. These things are small so you can potentially put them in any number of places. I did not take photos of the headlamp option because I was wearing it on my head at the time. The illumination area will be comparable to the cheaper flashlight that has the wider illumination area. These photos show widest area possible. You can focus down to a very small intense spot. The headlamp is probably going to give you the most compact option without having to get the saw out. There is no reason these could not be used for reading spot lights like the ones on each side of the coucho.

The part numbers for these are:


Cree P4 3-Mode Adjust Focus LED Flashlight 1039(3*AAA Batteries)

by HMing SKU: A17570000U

YarmuiLED Focus Control Adjustable Strap Headlight Headlamp (3 x AAA)

by Yarmui SKU: A0867000AR


QirtieTelescopic & Pancratic Lens Flashlight

by Qirtie SKU: A0695000DF

The above photos were taken hand held with the camera set to 400 ASA and the lens wide open so there was a good bit of light for me to get these images. You can look closely and see the green in the grass.

Make sure you mount these things to something metal if at all possible and if you pull the LED chip out I would epoxy it to a metal plate to act as a heat sink. It is probably best to leave them in the tubes otherwise you loose the good optics.


Perry
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Old 01-28-2013, 08:25 PM   #2
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I had pretty much made the LED conversion over the last 7 or 8 years. It started with my wilderness canoe trips where weight and space and were a concern. The flashlight changeover was first along with a high quality LED headlamp. Then I converted my large AS flashlights. Then I realized that the Coleman lantern and a gallon of fuel was a waste of space and weight. I grabbed the LED mechanic's worklight from the garage, which has an arrray of LEDS and a hi/lo switch. It works quite well for a camping lantern. I have another little LED Lantern for just a little puddle light on the Picnic table.
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Old 01-28-2013, 09:09 PM   #3
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LED flashlights have come a long way. The first ones had little or no focus and the color was bad.

Perry
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Old 01-28-2013, 09:18 PM   #4
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Costco currently has 250 lumen flashlights that take 3 AAA batteries on sale for 3 for $15.... 3 x 3 x 1.5 = 13.5 Volts.. so you can wire them up in series and run them off the 12 V line.

These make fine spots; they are quite intense, though.

They are also cheap enough to leave in cars, trailers, tool boxes for just-in-case use.

- Bart
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Old 01-28-2013, 11:31 PM   #5
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Costco currently has 250 lumen flashlights that take 3 AAA batteries on sale for 3 for $15.... 3 x 3 x 1.5 = 13.5 Volts.. so you can wire them up in series and run them off the 12 V line.

These make fine spots; they are quite intense, though.

They are also cheap enough to leave in cars, trailers, tool boxes for just-in-case use.

- Bart
You have an extra multiplier of 3 in there... measuring one of my actual Costco "TechLite Lumen Master" 3xAAA battery carriers confirms it, 4.32 volts on the Fluke with a set of batteries that have been in there for a while.

They're quite nice flashlights, though. If they didn't have the seizure-inducing flash mode that I accidentally access from time to time they'd be great. We have on in the Legacy Wagon, one in the WRX, one in the F150, one in the Argosy, plus 2 in the house.
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Old 01-29-2013, 12:56 AM   #6
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You have an extra multiplier of 3 in there... measuring one of my actual Costco "TechLite Lumen Master" 3xAAA battery carriers confirms it, 4.32 volts on the Fluke with a set of batteries that have been in there for a while.
.
Ah, but if you hook all three lens in series .... then you have 13 volts or so.
Quite the thing for blasting out some light - 750 lumens ... and for less than half the current in the single stock overdoor light.

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Old 01-29-2013, 01:05 AM   #7
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OH! 3 *flashlight heads* in series... I didn't understand that part.

I don't think I'd want that glaring at me while I was walking toward my trailer, sheesh! I recently characterized the settings (on a single flashlight) as "too bright, eye-searing bright, and seizure-inducing blink."
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Old 01-29-2013, 03:04 AM   #8
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The flashlights produce less glare because the beam is directional as opposed to going all over the place. If they are pointed down you don't get glare from wasted light that you get from these multi-LED arrays. If you look in the photos the light from the scare light is wasted and it hits you right in the face. This is why ZEP put an eyebrow on his.

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Old 01-29-2013, 09:13 AM   #9
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The flashlights produce less glare because the beam is directional as opposed to going all over the place. If they are pointed down you don't get glare from wasted light that you get from these multi-LED arrays. If you look in the photos the light from the scare light is wasted and it hits you right in the face. This is why ZEP put an eyebrow on his.

Perry
I've never been sad that the original owner of our Argosy didn't buy the scare-light option, unmodified the light is pretty terrible from those.

I use one of the of multi-LED "pad" arrays for the door light, set back about 3/4 inch from the translucent plastic cover. You can still see individual LEDs if you look directly at it, but the light is pretty diffused and lights an area on the ground around the door that's usefully sized and shaped. I had to cobble together a holder to keep the LED pad in approximately the right position, though.
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