What's it Going to Be ? Red or Green LED Compass Light ?

[noelex 77]

Originally Posted by Wireless1

polycarbonate has a high resistance to UV....but not a total resistance. Do you have any numbers on the percentage of filtration?

Most polycarbonate polycarbonates have a T=0 of 395 nm so virtually no UV, but Polycarbonates scratch very easily so compass manufactures probably use a hybrid plastic, but my guess is most domes will not transmit enough UV for your idea to work.

[dacust]

Originally Posted by Wireless1

Well, I see one disadvantage to UV LED's for compass lights. They are between $49 and $99 EACH! (Depending on what lens you select). WOW! I had no idea they would be that expensive. If anyone has a cheap source let us know...

...

I would buy the raw LED and make my own housing, or as stated by someone, get it inside the compass housing itself.

60 cents:
==> ledwholesalers 382.5 - 385 nm Ultraviolet UV LED 7001uv385 : UV Ultra Violet

-dan

[Paul Elliott]

Originally Posted by noelex 77

Most polycarbonate polycarbonates have a T=0 of 395 nm so virtually no UV, but Polycarbonates scratch very easily so compass manufactures probably use a hybrid plastic, but my guess is most domes will not transmit enough UV for your idea to work.

But if the compass cards use phosphorescent markings, and these get charged by the sunlight shining through the dome...

I don't recall ever seeing my compass glowing by itself at night, but the only time I would have noticed that was when the internal LED wasn't illuminated. I've got mine wired to both the tricolor and the deck-level running lights, using a pair of diodes to isolate the two circuits.

[Wireless1]

Originally Posted by dacust

I would buy the raw LED and make my own housing, or as stated by someone, get it inside the compass housing itself.

60 cents:
==> ledwholesalers 382.5 - 385 nm Ultraviolet UV LED 7001uv385 : UV Ultra Violet

-dan

Thanks for the link! Great job. The prices I quoted were from SETi and they specialize in industrial stuff. It was late and I didn't do a really good search. 50 to 100 bucks seemed to me at the time 'military' prices...you know, like the $400 toilet seat. Great to know there are UV LED's and "street prices" out there. Thanks for the link!!

[senormechanico]

Let's say you install the UV LED.
The numbers and lines glow white.
Your eyes are perceiving white light.
Why not just use white in the first place?
The white LED (I installed in my Ritchie compass in its original black plastic cover) doesn't illuminate anything but the compass disk markings.

What am I missing?

[hellosailor]

"Your eyes are perceiving white light.
Why not just use white in the first place?"

Because the glow emitted from a few markers and letters, even if it is white, will be a lot less than the amount of white light emitted when the whole compass has a light shining in it.

Even the US military walked away from red night lights ages ago. With LEDs now for under five dollars anyone can buy white, blue, green, red, amber and UV and a dimmer to use with all of them. Use whatever makes you happy and works for YOUR eyes.

But if you are not using dark sunglasses all day, don't worry about might vision. You won't have any regardless of the color of your lights. You may think you do, but you don't.

And forget about eating carrots, that was actually allied psyops to conceal the fact that RADAR had been invented and put into use. To keep the secret, they "leaked" the fact that they were feeding pilots carrots to enhance their night vision.

[sushirama]

Originally Posted by Wireless1

Well, I see one disadvantage to UV LED's for compass lights. They are between $49 and $99 EACH! (Depending on what lens you select). WOW! I had no idea they would be that expensive. If anyone has a cheap source let us know... The first of the week I'm going to call the tech rep at Sensor Electronic Tech, Inc. and see what they say about use as experimental compass lighting and also what lens type they would recommend. They also come in a wide range of frequencies (240nm to 360nm) and I have no idea how that would translate to making the compass markings (white) in my Richie Globe Master stand out. Also, I've discerned from their literature that one should NOT look directly into the LED lens. This should not be a problem with the compass as it has a hood over the light. Still, I wonder about reflections...

I get pure UV LEDS from Hong Kong on ebay. Like 15 bucks for 50 with limiting resistors included. I backfitted a standard 15 led flashlight with them. it was cool in the dark.

If you wanted why not get a multicolor RGB LED and fit in the slot. The switch can be a potentiometer that can make it color you want based on your mood and use situation. Cost would be about 5 to 10 bucks. Im doing that on my globemaster. And cockpit, basically everything i can convert.

[noelex 77]

Originally Posted by hellosailor

Even the US military walked away from red night lights ages ago..

They stopped using red because it's imcoptable with night vision equipment.

Sunglasses during the day do help night vision, particarly if the wearer is exposed to very bright light, like a ski field, but the effect is small compared to to the effect of equipment illumination.

Very few westerners do not get enough vitamin A for night vision, but it is a significant problem in third world countries. A lack of vitamin A can completely destroy night vision, but for the readers of this forum carrots are unlikely to make any difference to night vision.

[Wireless1]

I just bought 10 each of 380nm UV LED's for ten bucks. I'm going to have fun playing with them. However, I won't be drilling any holes in the globe of my Richie Globe Master until I KNOW what will work and what won't. There are some inexpensive compasses out there I can trash first.

[Blue Stocking]

And to get the thread drift on course--the reason for many fire trucks giving up the traditional red was because under sodium vapor street lighting, the red wave length becomes brown

[noelex 77]

Originally Posted by Blue Stocking

And to get the thread drift on course--the reason for many fire trucks giving up the traditional red was because under sodium vapor street lighting, the red wave length becomes brown

It's also difficult for some colour defective observers to see. Some colour defects reduce the intensity of red light so they can have difficulty seeing there is a light at all not just a difficulty detecting the colour.
This has caused many accidents with people not noticing a red warning light has been activated even when the light is bright and obvious to observers with normal vision.
Red was a poor choice for a warning colour.

[Paul_Carroll]

OK, so you go 16,000x more information then you ever wanted! I would suggest that you give yourself a means to DIM the light whatever you use. The light that is right for some situations will be WAY too bright on a truly dark night!
For my system I just worked in a little 1.5K potentiometer underneath where I can get to it to tweak the brightness as I like.

[Wireless1]

Originally Posted by Paul_Carroll

OK, so you go 16,000x more information then you ever wanted! I would suggest that you give yourself a means to DIM the light whatever you use. The light that is right for some situations will be WAY too bright on a truly dark night!
For my system I just worked in a little 1.5K potentiometer underneath where I can get to it to tweak the brightness as I like.

I trust you left about a 470 ohm resistor in series with that pot so you don't burn out your LED?

My 10 UV LEDs haven't arrived yet. Can't wait to see how they work.

[Wireless1]

Originally Posted by noelex 77

Most polycarbonate polycarbonates have a T=0 of 395 nm so virtually no UV, but Polycarbonates scratch very easily so compass manufactures probably use a hybrid plastic, but my guess is most domes will not transmit enough UV for your idea to work.

UPDATE! I finished my UV compass light experiment and the above "guess" about the Richie dome not transmitting enough UV is not true. Plenty of UV gets through from the same mounting place as the factory red LEDs.

I was able to fit the original two red LED's in the original bracket in the SP5 Globe Master plastic housing and also was able to squeeze the UV LED's under the same brass clips. I have a selector switch and a 50K ohm linear taper potentiometer in series with the supply voltage. So now I have the most beautiful purple-ish white glow on all my compass markings, but there is no bright visible illumination like there is with the red LED's! I can dim the red or UV LED's nearly all the way down but not quite off so that will prevent "dummy" here from turning on the compass light, and having the brightness control all the way down, see nothing and wonder why they aren't working! LOL. I'm happy!! So if anyone else wants to try this...I can personally attest that UV LED's illuminate the Richie SP5 compass card just fine and it does work nicely.

[noelex 77]

Glad to hear it worked out.
See if you can test your night vision with the 2 alternatives to see if the reduced spill from the UV compensates for the loss of red.
I think you will find the UV option better when only partially dark adapted but worse when fully dark adapted.