# Beacon Light



## sunny_nites (Dec 4, 2011)

There seems to be a lot of interest in these beacon lights so I took some advice and split this out from my “modded keychain” post.

I got the inspiration for these from *calipsoii* and his lamplighter project. If anyone is interested in buying something like this, check in with *calipsoii* . There was some discussion on his post about possible sales but I haven’t seen an update in a while so I’m not sure what the status is.

This post is for info on how I built my version, in case you want to try something similar as well as future upgrades and hopefully ideas from some of you.

And now on with the show.

The intention for these lights is to run them on incredibly low current for an unusually long time. The obvious purpose is, of course, to act as a beacon to allow you to find something in the dark, ie. Keychains, flashlights, etc. Think of them as something along the lines of a GID fob or maybe a trit.

I built a couple of beacons using the common current regulation circuit but don't really think it adds much to the abilities of the light (let me know if interested and I can provide more details on the circuit, printing, etching, components, etc). I ended up just using a 220kohm SMD resistor to limit current to something less than 10 micro amps. My meter only goes down to 10 micros and the LED draw won't register so they are running at something less than that. Looking for a meter that goes lower to get a better idea of what the current consumption is exactly.

I've built two different sizes; one that uses LR44 (200mah) batteries and LR621 (30mah) batteries. In theory, the LR621s should last around 6 months and the LR44s could last a couple of years. That's all theoretical of course. I've only been running them for a couple of weeks or so.






Lights out.





The real trick to this project was finding the “right” LED. I tried every type I could think of; SMD, 5mm, 3mm, domed, low domed, frosted, clear, every color available, UV with reactive phospher coatings, etc. What I found that worked the best was this odd looking 5mm (clear or colored, didn't seem to make much of a difference) unit with the dimple in the top. Not sure what these are officially called (thanks to *VegasF6* for the name of these LEDs: inverted cone) but I've seen them used in a lot of Christmas lighting. The point on the inside of the dome actually creates all the magic and it makes the lights appear much brighter than they have any right to be. Also, the LED color made a huge difference, green and Blue were the clear winners.









_Last edited by sunny_nites; 11-29-2011 at__ 08:20 AM__._

The LED pictured above is actually a red and green unit in one package. You change the color by reversing the polarity of the battery.

Probably the hardest part of the build for me was creating the round circuit board. I had been cutting them to the approximate size and sanding them into shape. I just got a hold of some circular metal punches that show some promise. I’ll provide an update when I have a chance to work with them a little more.

The circuit is really simple. I just used a dremel to make to make two cuts on the board rather than etching them.





This is a finished board made with only two cuts and two holes for the LED. The microscopic grain of sand bridging two of the cuts is the 220meg SMD resistor. The brass clip holds the batteries together and provides the ground. I tried several methods of insulating the clip but everything proved too big to allow the batteries and circuit to fit into the container or too unreliable. I finally found a cheap and easy solution in clear scotch tape.





Have to use something to insulate the circuit except for the single contact for the other leg of the LED. I use liquid electrical tape. You want to build up the contact for the led with extra solder to get it above the insulation and to allow it to connect to the battery adequately.





The larger beacons were made with 1/2" ID poly-carbonate tubing and 1/2" poly-carbonate rod. They are fairly large in size but work well on a key chain. The smaller beacons were made with the plastic portion of pill holders as in the picture above. But note they are all not made the same! Both pill holders were purchased from the same place but several months apart and they are different. The one on the right has a plastic lid and the beacon circuit and batteries fit perfectly. The unit on the left has a metal lid and at first I thought would be a great improvement over the plastic but It turned out not to be so easy.






It's a bit hard to see because of the glare but notice that the holder on the left has thicker walls than the holder on the right? Unfortunately, that makes all the difference and the LR621 batteries will not fit with the ground strap. That being said, I have been working with these holders and there may be hope. I was able to mill a channel inside the plastic for the strap and it may just work. I need to make a smaller circuit board as well to really try it out. 

Stay tuned!!


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## mat_the_cat (Dec 4, 2011)

Would it make any significant difference to the current which (5mm) LED is used? I can't see that it would matter that much so I could quickly connect up something at work - we can go down to 10nA but not sure to what accuracy without checking.


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## sunny_nites (Dec 4, 2011)

I haven't measured the difference in current between different types of LEDs, ie. 3mm, 5mm, SMD, etc but at the same voltage and resistor combination, there is a difference in how much current is drawn by color, because different colors have different voltage drops.

The thing I was really surprised by was the difference in brightness between different colored LEDs running at the same current. Not sure if it is the sensitivity of our eyes to different colors or the efficiency of the materials that generate the color or something else entirely? 

I'll try to get a comparison shot of some of the different colors I looked at so you can judge for yourself.


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## sunny_nites (Jan 21, 2012)

Still Having fun with calipsoii's lamplighter inspired beacon lights.

Pretty much settled on lithium CR2032 and 1632 batteries to power these little guys. I found some 3mm blue inverted cone LEDs and they allow for a really small build. Still green and blue are by far the most efficient.






Driving these little guys at 5 micro amps. I tried several different current loads and really think the 20 micro amps I was running the original lights on was too bright. Tried 15, 10 before eventually settling on 5. Might be hard to imagine but you really don't want these lights to be too bright as they are really just to help you find your keys or a maybe a flashlight in the dark and not serve as a night light. The 5 micros gives a great run time too. 






At 5 micro amps, you can barely tell they are on in daylight. In the dark it's an entirely different story.






I tried several different methods of attaching the leads to the battery; heatsrink tubing looked promising at first but proved to be unreliable, wire glue worked great but didn't look good on the finished lights (as you can see on the two in the picture above). Finally settled on plain old clear scotch tape. It is very inexpensive and completely reliable. Good thing as you can't fix it once the polymer has cured!






Got my hands on a couple of CR2450s, the mother of all lithium coin cells. 






It makes a really big light as compared to the little guy rocking the CR1632 but with 560mah on tap, it could in theory run for over 10 years! Check back in around 2022 for an update.






So, I had a lot of experiments that didn't turn out so well for a variety of reasons. What to do with carcasses? Most of them were running fine but the polymer didn't cure right and they were tacky or foggy or had some other cosmetic issue. I had been tossing them into a small polypropylene cup when I had an idea. Just fill in with more resin :naughty:






For the moment, my wife is patiently indulging my wish to display my "sculpture" but it wouldn't surprise me to much if it didn't suffer an accident some day, along the lines of the leg lamp in "Christmas Story".

Thanks for looking.


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## FRITZHID (Jan 22, 2012)

well, inspired by "lamplighter" and "Beacon light" i decided to tread these waters as well.
my wife has a slight addiction to Peeing on a stick (preg tests) and on occasion uses the electronic tests, of which my natural curiosity peaked & i just HAD to take one apart and see how it works, low and behold what do i find, but a CR1616 3v lithium cell and 3 SMD LEDs as well as a decent selection of other SMD components!
in this photo, you can see the main board which i cut on the red line, the 3 leds, batt holder and other various components. i used an inverted cone netural white LED from a string of x-mas lights, 2 SMD resistors found on the test board and a drillbit to drill the holes for the led leads by hand.





here is the board, and led all together.





where on the original board i soldered the resistors and LED





Batt, board and LED all together and lit.





after the epoxy hardened. (i must say i'm a tad disappointed in the epoxy job but it's what i had handy) i even used one of the pee sticks protective caps as a mold! 









and shots in the dark....








this one is probably closest to actual brightness






this all came to mind after seeing these as a calumniation of realizing my wife needed a better way to find her keys, use of parts normally thrown out and putting to use the knowledge of others ideas here on CPF. thanks guys!


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## sunny_nites (Jan 22, 2012)

Excellent recycling of the most advanced technology you will ever pee on!


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## eh4 (Jan 22, 2012)

This is a wonderful project, thanks for documenting it for us.
Surely you've seen promotions of future battery charging for smartphones and such where you just set them on a pad and the batteries are recharged with EMF?
This could be worked into your project as well, completely sealed, periodically recharged! 
-Or a tiny, tiny solar panel. ;-)


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## sunny_nites (Jan 22, 2012)

Thanks for the interest, eh4.
I have been following wireless charging progress with great enthusiasm. I haven't seen any equipment small enough for something like a beacon light yet but I'm hoping there will be in the not too distant future.
Good idea about solar charging too, I do have several small panels and some rechargeable coin cells that would probably work. I'll post some pictures when I have a chance to give it a try.


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## moderator007 (Jan 23, 2012)

Been following this for awhile. Great job by the way! Did you ever try a circuit that would flash ever so many seconds. I would like to make one with a flashing beacon. I have seen some small flashing circuits just wondering if you had tried any of them or know which one would work good with a low current draw.


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## sunny_nites (Jan 23, 2012)

I have played around with a few blinking and color changing lights and circuits. The color changer LED I looked at has the circuitry built in so it was pretty simple to work with. Problem was it needed at least 10mah to run. Similar issue with the blinking LED with the built in circuit. They need too much juice to run embedded and non rechargeable. I took a look at this circuit but haven't played with it yet:
http://www.discovercircuits.com/H-Corner/lowpwrflasher.htm
I believe it is similar to what comes built into some off the shelf lights. I have a Coleman lantern with a similar circuit. It blinks briefly about every 3 or 4 seconds and would likely have a good run time. Definitively on my list of circuits to try out.


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## sunny_nites (Jan 23, 2012)

This is another build I tried. It is from a thin wall polypropylene test tube.

Technically, it is not embedded but the epoxy has it more or less permanently sealed. It is running at 10micro amps on 3 x LR44 batteries with a 200mah reserve. Should run for at lest a couple of years.


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## mash.m (Jan 24, 2012)

hi,

i started with ultra low current some years ago with high power cree emitters. they start to glow at 50µA. with an 36500 lion battery they will glow for many moths/years.
on my last mod (a lummi raw) i did the same again, but with smd led´s. i must try out more then 20 types before i found some that glow bright at the ultra low current. maybe you should give the smd leds a try to make your builds a little smaller. these builds are looking so good:






this is my raw:





the four 0603 smd led´s start to glow at 3µa. with this current you can see them really good at night. on the picture obove they "glow" at 200µA so i can also use it as nightlight. i recharge the battery every week so the current draw of 33mA/week is no problem.

markus


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## sunny_nites (Jan 24, 2012)

Great build mash.m!

I settled on the inverted cone LED because they offered the brightest bang for the buck that I have been able to find so far. The tip of the cone really does the trick. It provides a reflected point of light away from the die or any other obscuring electronics and allows a very wide view. I haven't been able to find that in a SMD LED so far but I admit I have only been able to scratch the surface. There are probably hundreds of styles of SMD and some of those may work even better, I just haven't run across it yet.

The other draw for the inverted cones is their low cost. Around December and into the first part of January, you can pick them up for pennies a piece!

More than the LED, the batteries in my builds have been the limiting factor for size. Since these are embedded and the battery can't be changed, I wanted to be able to run the light for at least a year or more. That required batteries that could put out at least 100mah. All the EDCs I carry are flat so I naturally looked at lithium coin cells. Since a single cell with provide enough voltage to run a green or blue LED it also allowed a much simpler build as compared to stacking three or four 1.5v cells.

That being said, I am working on a 3mm blue unit that will run on some tiny silver oxide cells (probably won't get a year of run time from this one). Should be crazy small. I'll post some build pics as soon as I can.


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## AnAppleSnail (Feb 6, 2012)

sunny_nites said:


> More than the LED, the batteries in my builds have been the limiting factor for size. Since these are embedded and the battery can't be changed



I've actually been parting out ideas for (Bigger-scale build thread here) making the battery recharge, and keeping things small.

1. Tiny USB flash drive



not much bigger than the USB connector
2. Trickle-charged 3xNiMH button cells in series
(The neatestI can find are about 80 mAh at 6x15mm)
3. Build as above, pot in epoxy.
Result:
Recharging USB storage that finds your keys for you.

The overall size will be not much bigger than that CR2032 build, but thicker. I think it's about right for keychain carry, but I haven't been able to build it yet.


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## Darvis (Feb 7, 2012)

I have a dumb question, but is the circuit for this build simply battery+resistor+led?

So you have your cr2032, the LED and a resistor that takes it down to an output level that seems dim/bright enough?


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## AnAppleSnail (Feb 7, 2012)

Darvis said:


> I have a dumb question, but is the circuit for this build simply battery+resistor+led?
> 
> So you have your cr2032, the LED and a resistor that takes it down to an output level that seems dim/bright enough?


Yep. And my charging circuit has two resistors - one for the trickle charge (a few hundred ohms) and one for the LED (Pick for dimness)


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## Darvis (Feb 7, 2012)

Wow, thanks AnApple!! I thought it might be that simple, but was doubting myself.. thanks for confiming, going to begin building one of these today. I have tons of red LEDS from my Joule Thief project, and as many 2032's and resistors. This is excellent!!!


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## AnAppleSnail (Feb 7, 2012)

Darvis said:


> Wow, thanks AnApple!! I thought it might be that simple, but was doubting myself.. thanks for confiming, going to begin building one of these today. I have tons of red LEDS from my Joule Thief project, and as many 2032's and resistors. This is excellent!!!


Enjoy! Just to confirm - don't try charging CR2032s. I was charging NiMHs.


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## Darvis (Feb 7, 2012)

I appreciate that, no.. don't want exploding beacons, just glowing ones.


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## Darvis (Feb 7, 2012)

Was busting my noodle on how to build one of these without going the glue and epoxy route and settled on this:






I have tons of these (seem to get one with just about any order these days) and it seems like it might just do the trick. Has a neat, on off switch, comes with batteries that can be changed, etc. I'm going to add my new choice of LED and resistor and see how it works. 

The best thing is that it's keychain ready and no worse than any building access fob. 

It's not waterproof, but maybe it does not need to be..


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## Darvis (Feb 7, 2012)

And here it is built and deployed. Hard to see in daylight, but glows great in the dark and had to sand the red led so I could see it from all angles. I ordered some blue and green wide angle view ones and should have them soon

I think this took me 10 minutes to build...


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## AnAppleSnail (Feb 7, 2012)

I don't have a drill press to try this, but I wonder if one could make any LED 'cone-tip' for all-around visibility with a drill press and a 5mm+ drill bit? Carefully poking a cone into the end is about all that should be needed. I think the 'point' of the cone should be rounded, though... maybe a hot poker with a rounded-cone shape?


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## Darvis (Feb 7, 2012)

Not sure, but sanding the LED did a fair job for me. I did have to play around with the resistor values until I got just the right glow, in this case, 180k.. but it worked out

If even get 2-3 months out of this, I'll be happy!


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## AnAppleSnail (Feb 7, 2012)

Darvis said:


> I did have to play around with the resistor values until I got just the right glow, in this case, 180k.. but it worked out



I'd like to see how you worked the resistor in. Did you cut one LED leg short and put a peg-leg resistor in place of it?


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## Darvis (Feb 7, 2012)

Exactly, yes- just a plain old peg leg carbon film resistor. I'll snap a photo of how I pieced it together. For this first run, I didn't even bother to solder anything, I just twisted and taped to see if it would work and it ended up being pretty good, so I put it together.

I do plan on making more robust/permanent when the new blue and green LEDs arrive, but for now, I'm going to beat on this and see what happens. I threw it a few times and it help up, so.... 

EDIT: Here's a duplicate of the one in my fob..


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## FRITZHID (Feb 7, 2012)

AnAppleSnail said:


> I don't have a drill press to try this, but I wonder if one could make any LED 'cone-tip' for all-around visibility with a drill press and a 5mm+ drill bit? Carefully poking a cone into the end is about all that should be needed. I think the 'point' of the cone should be rounded, though... maybe a hot poker with a rounded-cone shape?



i've used a fine tip soldering iron for this in the past (in the 90's) before they even had cone tipped LEDs for various applications. it works well if you use a clean tip and then trim off the excess with a razor.


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## Darvis (Feb 7, 2012)

Just tried drilling one... did not end well, I would suggest the soldering iron thing or actually finding cone LEDs.

I didn't break the LED, but the drilling did not have the desired effect at all and just made a mess. Sanding is far better.


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## AnAppleSnail (Feb 7, 2012)

Darvis said:


> Sanding is far better.


Aw. Thank you for trying. I have some warm-white cone LEDs to try at semi-low current levels. I'm still hooked on building rechargeables, which allows higher drive levels.


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## sunny_nites (Feb 7, 2012)

Sweet build!

I've tried to drill a few cones as well and have been disappointed with the results. The inside of the cone really needs to be polished to work efficiently. I could see it being done but would be a crazy amount of work. Sanding the outside works well and gives a good diffuse glow for any of the standard round type LEDs that I've tried it on.


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## Darvis (Feb 9, 2012)

Hey, if you guys are interested, found some really nice blue and green LEDs from Super Bright Leds .com

These are the 120 degree 1200 mcd model RL5-B12120 for blue and the green are the RL5-G161120

They have a cone built into the mold that's hard to see at first, but it's there and it appears to be metal. Great visibility from all directions.

I bought the pre-frosted 360 degree versions as well, also nice..


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## Darvis (Feb 9, 2012)

Ok, and sorry if I'm getting annoying here, but here's the build I was hoping to get to...

I managed to save the switching mechanism, so now I can turn the beacon off in daylight for even more insane runtime. This is the guts of the mini light with a 330k resistor, on/off capability and the ability to readily change batteries. This is with the blue LED in my above post.

Crappy pictures, but here's the build:

Resistor soldered in...






Trying to show the whole build here and the pos connection..






Completed light..






Glowing...


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## AnAppleSnail (Feb 9, 2012)

Darvis said:


> I managed to save the switching mechanism, so now I can turn the beacon off in daylight for even more insane runtime.


I toyed with the idea of one that cuts on in the dark, but I can't think of any circuit that will take less power than the running LED. It also seems to me like turning off the beacon will lead to losing your keys more easily. I wonder if passive optics can make GITD much more visible at low brightnesses?


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## Darvis (Feb 9, 2012)

An interesting idea with the GITD, they'd have to be optically clear or the light loss through the optic may negate the gains of the magnification? Not sure on that.

True on the switch by the way, but it is a very stiff switch and would not turn off easily.. so, what I'm getting at is that you could just leave it on and let it go.


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## AnAppleSnail (Feb 9, 2012)

Darvis said:


> True on the switch by the way, but it is a very stiff switch and would not turn off easily.. so, what I'm getting at is that you could just leave it on and let it go.


I've got some like this with mechanical switches. If I get mine to work with the switch, I'd probably turn the beacon 'on' when I leave work and off the next day at work. +1/3 battery life already.


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## Darvis (Feb 9, 2012)

AnAppleSnail said:


> I've got some like this with mechanical switches. If I get mine to work with the switch, I'd probably turn the beacon 'on' when I leave work and off the next day at work. +1/3 battery life already.



Exactly!!! I want to get as much out of these coin cells as possible.


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## calipsoii (Feb 9, 2012)

Darvis said:


> Exactly!!! I want to get as much out of these coin cells as possible.



I wouldn't worry about it too much. My runtime-test Lamplighter has been lit 24 hours a day on it's first set of batteries since October 3rd and shows no signs of dimming. The current draw on these are ridiculously low.


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## sunny_nites (Feb 9, 2012)

Excellent point calipsoii; two CR2016 bats (90mah) driving a a blue LED with a 330k ohm resistor and your looking at approx a 1 year run time. Much longer if your using a single CR2032. 

Darvis, I really like your build and I hate to break it to you but the standby current on your switch is probably double what the LED will draw when powered on. Not sure what the circuit uses when running but it may still be drawing considerably more juice than just driving the LED with the 330k limit resistor.


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## Darvis (Feb 9, 2012)

sunny_nites said:


> Excellent point calipsoii; two CR2016 bats (90mah) driving a a blue LED with a 330k ohm resistor and your looking at approx a 1 year run time. Much longer if your using a single CR2032.
> 
> Darvis, I really like your build and I hate to break it to you but the standby current on your switch is probably double what the LED will draw when powered on. Not sure what the circuit uses when running but it may still be drawing considerably more juice than just driving the LED with the 330k limit resistor.



Ahhhhhh... I did not see that coming!!! Ah well, we'll see how this one does...

I ordered a bunch of different battery holders from digikey and bunch of those little lights from battery junction. The lights I have coming are translucent, so that may be cool.

I think I might trace out the circuit board from the light and make a dummy board out of my favorite circuit board material: Homer Bucket Lid plastic. Then just go direct drive.. these blue LEDs (which are excellent actually) are bright even at 330k, so I may try some even higher resistance, especially with the translucent lights...

I also built one that's now running on a CR123a and fit it through the front of one of my joule thief lanterns so I have locator on it as well, great for when I need it at night..

Yes, I'm a spaz, and yes, this is the coolest little project!!!


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## AnAppleSnail (Feb 10, 2012)

Darvis said:


> Yes, I'm a spaz, and yes, this is the coolest little project!!!


Turns out that epoxying an LED with a peg-leg resistor to a CR123 and a lanyard makes a grape-sized FindMe that will last until the aluminum flashlight rusts off


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## FRITZHID (Feb 10, 2012)

AnAppleSnail said:


> Turns out that epoxying an LED with a peg-leg resistor to a CR123 and a lanyard makes a grape-sized FindMe that will last until the aluminum rusts off


:laughing:lovecpf


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## Darvis (Feb 10, 2012)

Wanted to report back on the LEDs that I got... they're really nice, great visibility, clear and BRIGHT!!! Found that 330k was not enough and settled on 470k resistors and now the glow is just right, more tritium than flashlight on low.

Also reworked the design of the internals, ditched the switch and used lid material from a raisin can to make my battery lead "disc" Will post more pictures next week when I get the clear battery cases in.

Cheers!

D


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## AnAppleSnail (Feb 10, 2012)

I've got 4 oz of glow paint to play with. We'll see what becomes of it and how much winds up in art, and how much in flashlights. I do plan to see what glowpaint on a sanded LED does for glow-visibility and LED visibility. The paint itself is opaque in bulk, but I haven't used any yet.


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## sunny_nites (Feb 10, 2012)

Glow paint works great with UV light. If you have a UV LED give it a try. I'd be interested in seeing how it does.


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## FRITZHID (Feb 10, 2012)

sunny_nites said:


> Glow paint works great with UV light. If you have a UV LED give it a try. I'd be interested in seeing how it does.



that would be interesting with UV led and flasher, kinda pulsating with an after glow... call them FyreFly lights. lol


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## Lolaralph (Feb 12, 2012)

Darvis,
Did your resistors come from superbrightled.com also, I see they have some and I was going to order them when I send for LEDs, if they are the ones.


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## Darvis (Feb 12, 2012)

I actually got mine at the shack, but I imagine the SBLED ones are just as good, I would say go for it as long as the resistance level is what you want.. I would suggest getting a few different ones, probably the 330 and 470k to see which you like.

I went with the shack because they had a variety pack with all different ones.


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## moderator007 (Feb 12, 2012)

Just thought I would share. Good place to buy resistors and other small electroic parts. The site seems to be overseas. But when I order my parts they ship from the US, receive my order in a couple of days (may not hold true for some parts or all orders). I have read they have a warehouse in the US. From what I researched (before I ordered) the company seemed to reliable and have good customer service. Now I buy all my parts there that I need if they carry it. Shipping is quite reasonable compared to some. They carry several different types of resistors but only one size of smd resistors 805.


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## Darvis (Feb 12, 2012)

moderator007 said:


> Just thought I would share. Good to place to buy resistors and other small electroic parts. The site seems to be overseas. But when I order my parts they ship from the US, receive my order in a couple of days (may not hold true for some parts or all orders). I have read they have a warehouse in the US. From what I researched (before I ordered) the company seemed to reliable and have good customer service. Now I buy all my parts there that I need if they carry it. Shipping is quite reasonable compared to some. They carry several different types of resistors but only one size of smd resistors 805.



Thanks!! Good to know.. got some cool battery holders from Digikey yesterday and going to be working on a cool devcon & glow powder experiment tonight. If it works, I should have a translucent battery case that both glows from the LED and any daylight it catches. We'll see if the molds I made work tonight or not!


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## AnAppleSnail (Feb 13, 2012)

Too bad the idle current on a 555 timer is so high. I've been pondering a circuit that'll flash a UV LED into glow paint periodically to keep it charged. But I don't know enough circuits to design that, or enough glow physics to know what will create the most efficient dim glow.


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## moderator007 (Feb 13, 2012)

Have you guys ever considered a self flashing led? Wonder how low of a current it will work down to? I dont find any real specs on them.


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## Darvis (Feb 13, 2012)

OK guys, here it is.. slightly over the top:

Made a mold using play-doh and saran wrap and used a battery as an impression maker:







Devcon and glow powder:






Poured into the molds:






Makes a false circuit board:






In which I drill two little holes to make a battery contact "button"






This replaces the translucent light's innards (top left in photo):






And makes for the combo beacon/glow-light:






I'm classifying this in my: "this worked way better than I thought it would" department!!!

One thing to note, I had to "laminate" the devcon discs between some clear shipping tape for added rigidity, but they worked great otherwise...

D


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## scout24 (Feb 13, 2012)

These are way, way too cool. Just placed a SBLED order... Have these been tried with a 2032?


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## Darvis (Feb 13, 2012)

scout24 said:


> These are way, way too cool. Just placed a SBLED order... Have these been tried with a 2032?



Heck yeah!! Runs on either, 2x2016 or 1x2032.. I have one tapped into a CR123a in one of joule thieves as a locator as well. Anything matching the vf of the LED will do.


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## scout24 (Feb 14, 2012)

I couldn't wait for my sbled order, and went to Radoishack today...  Plagarizing Darvis heavily, used a blue fauxton to make a 2032 powered gren led version, w/ 1k ohm resistor. DIM locator, but easily seen from across a dark room. Used a black one with blue led, 2x2016's and a 2200 ohm resistor for about the same output. The 470 ohm will be next, but more for finding stuff as a very low-powered light than a locator. Thanks for the motivation! These are definitely too cool for school!  If the theoretical runtimes are even close, WOW...


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## sunny_nites (Feb 14, 2012)

In a word; Ingenious!


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## Darvis (Feb 15, 2012)

A few observations after a fair amount of tinkering and to support what Scout was seeing:

I've tested about 5-6 different LEDS and my favorite by far is the SBLED 360 degree frosted series in both green and blue (Models G2D-360). The 120 degree clear are a close second place

After many breadboard overnight tests, I've come to realize that Scout is right, the 330k and 470k ohm resistance levels are very very bright, especially in the translucent hosts and with the 360 degree LEDS. I've come to see the sense in the 1.5m and 2.0-2.2m resistance levels as they are truly equal to the 1.5mm tritium vials in output

The translucent hosts are the best by a long shot, letting all light through and "disappearing" in a keychain or BOB

I tried pouring devcon into the host halves to coat both sides, long story short, it's worth it to make the molds and discs!! Trust me on that one

I ordered some SMD resistors (thanks for the link 007!) so I aim to get the resistor as unobtrusive as possible and will reprt back on how that works. They were so freaking cheap, I mean less than a penny each, that I had to order about 700 hundred of them to meet the minimum purchase price. I will have a large variety to work with

Carry on!

D


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## AnAppleSnail (Feb 15, 2012)

moderator007 said:


> Have you guys ever considered a self flashing led? Wonder how low of a current it will work down to? I dont find any real specs on them.


I'll play with one I have back in hand sometime soon, and see what results I get at starved current levels.


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## moderator007 (Feb 15, 2012)

AnAppleSnail said:


> I'll play with one I have back in hand sometime soon, and see what results I get at starved current levels.


Looking forward to hear how they do. Incorporate a flashing led and Darvis idea with the glow powder maybe the way to go for me.

Darvis those smd 805 resistors are tiny. You'll need a very fine tipped soldering iron. There so tiny alot of times they will stick to the soldering iron tip if not held in place some how. I found the site while searching for potentiometer's for a pwm circuit. They where cheaper than anywhere else. Like you, a had to order more things than i needed just to place a order. I have since ordered several times and have a whole aray of components to play with.


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## Darvis (Feb 15, 2012)

moderator007 said:


> Darvis those smd 805 resistors are tiny. You'll need a very fine tipped soldering iron. There so tiny alot of times they will stick to the soldering iron tip if not held in place some how. I found the site while searching for potentiometer's for a pwm circuit. They where cheaper than anywhere else. Like you, a had to order more things than i needed just to place a order. I have since ordered several times and have a whole aray of components to play with.



Agreed, I have not seen one in person, but have played with the ZXLD chip so I have some idea.. and thanks for the tip on the, er.. tip!! I actually read up on soldering these little guys last night and am going to try the blob on the wire, back the resistor into it method. I do have to get me some micro tweezers though, so back to the Shack I fear!!


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## calipsoii (Feb 15, 2012)

Darvis said:


> Agreed, I have not seen one in person, but have played with the ZXLD chip so I have some idea.. and thanks for the tip on the, er.. tip!! I actually read up on soldering these little guys last night and am going to try the blob on the wire, back the resistor into it method. I do have to get me some micro tweezers though, so back to the Shack I fear!!



I use 0805 in most of my projects, including the first prototype for these lights:





My suggestion would be to melt solder onto your target first, let it cool, then hold your 0805 against the solder with your tweezers while applying heat with your iron. Once the first joint is soldered, do the 2nd joint, then return to the 1st one with a bit more solder. As moderator007 has mentioned, a fine tip will be very helpful.


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## sunny_nites (Mar 28, 2014)

Wow, been a while!

Really surprised at how well the batteries hold up on these little guys.

This one was made in February of of 2012 and is still proudly preforming keychain duty.






Hard to see the lights but my sculpture of early models is down from four working lights to two.





All the lights in the sculpture were built in November and December of 2011.

One thing I learned is that there has to be some kind of mechanical pressure to hold the wires to the battery. Tried may different methods but wire glue seemed to work the best for those flat style resin lights.

I've gotten away from making the encapsulated lights as I've learned that the batteries can vent. None that I have made have had a problem but I did move my sculpture out to the garage and I wouldn't recommend trying this yourself.

I've come up with a new model that I've been using for a while now. This one can even have the battery changed when it runs out.





Attached to my Thrunite T20





Has a mechanical holder for the wires as seen above.






I'm running this a little "hotter" than I would for a light that can't have the battery replaced. The light above is running around 8 micro amps on a fresh battery and should run for at least a year.






Hard to get a reference with the lights on to get the pictures but this light is vastly brighter than any tritium I have see, although it is admittedly much bulkier.

The cap is made of a stainless steel loop embedded in clear resin and surrounded by a semi rigid poly tube, that acts like an o-ring that helps make it water resistant. Not sure if I will go with some other mechanical method to secure the cap. Right not the cap is like a cork but is extremely tight and doesn't show any signs of coming out on its own.


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## Bimmerboy (Mar 29, 2014)

What a cool thread! Some pretty funny comments too. :thumbsup:

Subscribed... I'd definintely like to try making some of these. Thanks, guys!


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## alphazeta (Mar 30, 2014)

Q: does one use a decent/nice DMM to read the current? My sub $10 DMM gives me a current reading of zero on all settings.

I scrapped quickly one together with two L44 button cells(for a supposedly 3.10V) and a project leftover 2 ohm resistor + one generic 5mm LED. It is WAY too bright. I'll be surprised if it lasts the night.

BTW - needless to say -> cool thread!

BTW#2 - this light won't be living on my keychain but probably as a stationery light in some dark recess of my home. As space won't be a concern perhaps I should I should look toward building a find me kinda light by soldering a few D cells together?


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## sunny_nites (Mar 30, 2014)

I haven't run across a meter that will measure super low currents either.

I'm purely going by calculations on the current outputs for the lights I have put together:

LED VD = 2.4
Desired drive current = 4 micro amps
Voltage of a fully charged lithium primary button cell = 3.2v

3.2-2.4/.000004 = 200K (went with a 180K, have to do some rounding to match what is available)

To figure runtime:
Current capacity of cell (CR927 in the newest version) = 30mah
Current draw of LED = 4 micro amps (or there abouts)

(((.03/.000004)/24)/365) = .865 of a year or around 7 or 8 months.

The above calculations assume all everything is static, which it will not be with a simple resistor. What will likely happen is the brightness of the LED will dim but keep running way past a year.

Good luck on your projects and thanks for the comments! These have been fun projects for sure.


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## tylernt (Mar 31, 2014)

There is a device called "uCurrent" made by an Australian guy that goes by the handle of "EEVblog" and is sold by such retailers as AdaFruit.


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## pyro1son (Mar 31, 2014)

love this idea and have tried all my leds but none light at such low current


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## tylernt (Mar 31, 2014)

pyro1son said:


> love this idea and have tried all my leds but none light at such low current



What voltage are you using and what color of LED? If the voltage is high enough, your LEDs should light even at very tiny current levels. But if the voltage is too low, then all the current in the world won't make them light.


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## pyro1son (Mar 31, 2014)

Green LED @ 3.78 volts


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## tylernt (Mar 31, 2014)

pyro1son said:


> Green LED @ 3.78 volts



That's probably high enough. Each LED has a slightly different forward voltage, especially between manufacturers but even within a batch. 3.6V is thrown around as a "standard" but some LEDs are specified as high as 4.2V. But, even the ones specified at 4.2V will usually light at somewhat lower voltages, albeit with reduced brightness.

Is this a new battery and are you reading the voltage while it is attempting to light the LED? Voltage on a weak battery can drop significantly when a load is placed on it.


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## pyro1son (Mar 31, 2014)

It's a fresh li-ion I'm testing with. The LEDs are rated to have a 2mA working current.


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## tylernt (Mar 31, 2014)

pyro1son said:


> It's a fresh li-ion I'm testing with. The LEDs are rated to have a 2mA working current.


Hm, I can't explain it then, unless maybe you've got a bad resistor. Sometimes the resistance will be higher than spec due to manufacturing defects.


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## pyro1son (Mar 31, 2014)

I shall try some other resistors later


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## sunny_nites (Mar 31, 2014)

I have tried Lots of different styles and manufacturers of LEDs and found that the tolerances, when you get into the micro amp range, varies wildly.

In my experience:
Blue and green LEDs work the best, at very low currents, in general. Red, amber, white, etc take much more current to produce visible light.
This was contrary to the way I thought it would be: SMD blue and green LEDs don't work at very low currents, as well as 5mm and 3mm LEDs do.
Inverted cone LEDs by far work the best at producing visible light at extremely low currents.
When you get into the nano amp range, the ability of an LED to provide any light will vary depending on the individual LED itself. IE, some LEDs from the same manufacturer will work at nano amp range, some wont and the ones that do work will put out different levels of light. 
Around 800 nano amps appears to be the cutoff for any LED that I have worked with.

pyro1son, your LEDs may be putting out light but it might be too dim to see, especially if they aren't inverted cone types. Maybe try it in a really dark room or gradually decrease the value of your resistor until you start to get visible light. Once you know it is working, you can put a DC meter across the pins of the LED and measure the voltage drop to get their exact value.


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## pyro1son (Mar 31, 2014)

Thanks for the info. Very informative! I shall give that a go.


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## Dr.Jones (Apr 1, 2014)

If you want to measure the current, use the resistor as shunt, i. e. measure the voltage U of the resistor with resistance R and calculate I=U/R.


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## alphazeta (Apr 2, 2014)

Dr.Jones said:


> If you want to measure the current, use the resistor as shunt, i. e. measure the voltage U of the resistor with resistance R and calculate I=U/R.


Great tip! Thanks!



sunny_nites said:


> I haven't run across a meter that will measure super low currents either.
> 
> I'm purely going by calculations on the current outputs for the lights I have put together:
> 
> ...


Very useful 411. Thx!


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## danjcla (Jun 28, 2015)

*Which polymer to use?*



sunny_nites said:


> Good thing as you can't fix it once the polymer has cured!



Sorry for the newbie question, but which polymer did you use? Later in this thread someone mentions "devcon", but they make a whole lot of products. I found an epoxy resin called "Alumilite Amazing Clear Cast", 16oz for $16. But it seems to have a niche target market; I'm guessing / hope that something more industrial would be cheaper than $1 per ounce, even in small quantities.

Also, awesome thread. Comes in high for a lot of google searches.


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## DrafterDan (Jun 29, 2015)

*Re: Which polymer to use?*

Wow, not the longest 'wayback machine' post that has been resurrected, but this one is about 3.5 years old. 

I don't recall if S_N ever mentioned which resin he used, however I bet it was along the lines of those 2-part epoxy tubes that are available at any hardware store. I've used them several times, they do cure nice and clear. Just go slow to avoid bubbles!
~D


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## sunny_nites (Jun 29, 2015)

*Re: Which polymer to use?*

I really did a double take when I saw an update to this post!

Hard to believe but I have beacons going on 4 years old that are still working and even have a couple of beacons in that sculpture from page one that are still putting out light.

I tried a couple of different versions of epoxy but Alumilite seemed to be the best. I wouldn't recommend the two part Devocon type epoxies for several of reasons; they are very thick, very bubbly and will yellow over time or with much exposure to sunlight. Even the Alumilite can be tricky to get all the bubbles out. A vacuum chamber is recommended and would probably work the best but I used a pressure pot and it seemed to work pretty well and was vastly cheaper.

Now with that being said, I would recommend that you *not *encapsulate any type of battery because they can vent and it's hard to say what might happen to one encased in resin. 

A better idea would be to use a small, single LED keychain light and build your beacon in it. That way the battery is not confined in anyway. Something along the lines of this re-purposed X-Light Micro housing:





You would want to use some mechanical means of holding the terminals of the circuit to the battery, the leads for the LED are way to weak. The above example uses the spring clip from the donor circuit and holds the battery in quite nicely. And with that whomping 180mah capacity CR2032 battery providing power, this beacon should run for years and years.

Good luck and thanks so much for the trip down memory lane!


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## kaichu dento (Jun 29, 2015)

*Re: Which polymer to use?*

Norland 61 is probably the best epoxy for this. UV curing no-mix optical grade epoxy which it seems everyone on CPF was stocking up for trit installs. I've still got a bit stashed away but haven't paid any attention to trits in a while.


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## danjcla (Jul 1, 2015)

*Re: Which polymer to use?*



kaichu dento said:


> Norland 61 is probably the best epoxy for this.



The Norland 61 does look awesome, but you'd have to be made of money to do a lot with it... $30 an ounce. Whereas the "Alumilite Amazing Clear Cast" is $1/oz.


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## kaichu dento (Jul 1, 2015)

*Re: Which polymer to use?*



danjcla said:


> The Norland 61 does look awesome, but you'd have to be made of money to do a lot with it... $30 an ounce. Whereas the "Alumilite Amazing Clear Cast" is $1/oz.


There was a lot of disbelief when we first found out about the Norland pricing, but as there was so little needed to set a trit it became accepted. 
For Beacon Lights the Alumilite might well be the best, and Devcon and other epoxies that yellow after curing will be some of the worst. Anyone with the ability to build a small vacuum chamber will be able to minimize bubbles which form during the mixing process from remaining in the finished product.


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## kaichu dento (Jul 1, 2015)

Reading some reviews it looks like the ICE Resin Jewelers Grade Clear Casting Epoxy although a little more expensive option could possibly be another good option with some reviewers having cited slightly better clarity with concern to bubbles and coloration.


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## sunny_nites (Jul 2, 2015)

Been a while since I worked with resins but another concern is that some resins remain flexible to a degree after they cure or if they become warm, like say, from being carried in a pocket.

This flexibility can lead to equipment malfunctions with the embedded parts. If I recall correctly, polyester type resins (Castin' Craft, etc) seemed to be the worse while Alumilite appeared to remain structurally stable. One suggestion I've mentioned is to use a mechanical method of holding your circuit to the battery. Something that will put apply spring tension without shorting the battery like a metal clip would. Polyester tubing works well if you can find the right size that will fit on the battery and within your mold. Wire glue can work too but even that can loose connection if the resin is flexible enough.


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