Project Lamplighter - my homemade LED keychain fob

[calipsoii]

Can you tell me what kind of LEDs you ordered, brand, part #, etc.

Digikey part numbers
754-1130-1-ND
754-1133-1-ND
754-1437-1-ND
754-1438-1-ND

 

[DFiorentino]

You've inspired me. I just got in:

516-1396-ND
516-1397-ND

Both of these have a Vf low enough to not need any circuitry when run off of a 1.5V watch watch battery (379). I need to make myself some new test leads for my Fluke, however as the current is so low, the resistance in my old leads is throwing my readings off. Still as bright or brighter than the tritium vials I have, however.

-DF

 

[BobVA]

oo:

Wow, that's pretty crazy. Definitely going to give that circuit a try when I get a chance. ...

Awesome - Keep us posted and thanks for the feedback on the Kingbright green!

(I've got the circuit printed out and on my "to do" list, too.)

 

[3zuli]

great idea! I made one on Sunday (after reading this thread), just a red smd led connected directly to a LR44 (1.5V) button cell battery. it glows! let's see, how long it lasts.

I want to try this flasher: http://www.discovercircuits.com/DJ-Circuits/OSC4.htm (the one on the right)

 

[calipsoii]

You've inspired me. I just got in:

516-1396-ND
516-1397-ND

Both of these have a Vf low enough to not need any circuitry when run off of a 1.5V watch watch battery (379). I need to make myself some new test leads for my Fluke, however as the current is so low, the resistance in my old leads is throwing my readings off. Still as bright or brighter than the tritium vials I have, however.

-DF

Nice! I like the idea of those LED's - do you find the long leads off each side make them easier to work with? Can we get some pictures of the final product?

great idea! I made one on Sunday (after reading this thread), just a red smd led connected directly to a LR44 (1.5V) button cell battery. it glows! let's see, how long it lasts.

I want to try this flasher: http://www.discovercircuits.com/DJ-Circuits/OSC4.htm (the one on the right)

Looks awesome! Did you find it difficult soldering directly to the battery? I've never tried out of fear of overheating it and having it blow up in my face. The few times I've tried to solder leads to rare-earth magnets has been traumatizing enough...

 

[DFiorentino]

No final product yet as I'm just beta testing different parts and ideas. I prefer red myself, so I'll likely won't test any other color possibilities. Here are some quick comparo shots with some tritium vials and some tritium keychain markers. The LED in the upper left is a 516-1311-ND (3mm) and the one to the lower left is a 516-1397-ND. The 1397's leads may be a nice touch or could be a hindrance according to the final host I decide on. I will say they are VERY frail/delicate to handle.

Pics descending in exposure; starting with 15 seconds...

#1

#2

#3

#4

#5

#6

#7

#4 is pretty close to what my eyes see. And this was taken in an almost dark room, save the LED stand-by lighting from my many digital/electronic devices.

-DF

 

[DFiorentino]

I may try driving 5 or 6 of these LEDs off of a small 9V A32 battery I just got. If I can keep the current low enough, it would make a nice 360 degree keychain marker. Don't know how long it would last though...

-DF

 

[3zuli]

Looks awesome! Did you find it difficult soldering directly to the battery? I've never tried out of fear of overheating it and having it blow up in my face. The few times I've tried to solder leads to rare-earth magnets has been traumatizing enough...

It's a bit tricky, but pretty simple: just sand the place, where you want to solder and use some soldering paste. I recommend to use 100W soldering iron, because you want it to be able to heat up the entire battery quickly. also, use a vice to hold the battery while soldering, this makes things a lot easier.

 

[adubbz]

Very cool, Calipsoii!!!

They look very awesome and are so simple(not that I could ever do it ) and sweet. I would buy one if you ever make more???

 

[calipsoii]

Hi all!

Well, I'm happy to say that the runtime test continues - it just passed the 1 month mark and shows no signs of stopping. :thumbsup:

I mentioned a while ago that my new LED's arrived, but it took until today to find the free time to sit down and try them out. They're easily a few times brighter than the original red one I made and the green is very eye-catching in the dark.

I'm trying a new surface treatment that'll hopefully keep the top nice and transparent. Hot glue seems to pick up a ton of lint and scratches and after a couple weeks in your pocket it just doesn't look that good. I'll let you know how this one holds up.

 

[tylernt]

I love the green! I wonder if you can get an aqua/cyan/teal/505nm SMT LED. Our eyes are very sensitive to that wavelength.

BTW a coat or three of superglue over the hot glue should make for a pretty tough surface.

 

[archimedes]

It's kinda/sorta a little bit like a see-thru ZA-4 Firefli ? Those have been tough to find for quite a while.

Is it on/off ? Or constant on for glow?

I would be interested in these if you plan to make them available....

 

[nein166]

What happens if the battery dies in the night and you need your keys, you won't be able to see where it is.
You need redundancy! Could you use that tritium keyfob as the plug in the battery end?
Heating the tubing with a hair dryer should make it pliable enough to drop the batteries in and shove it over the trit fob.

 

[sunny_nites]

Take a look at two part, 5 minute epoxies for a top coat over the hot melt glue. In thin coats it is clear, (thicker coats would have an amber tint) very hard and does not attract lint. It does tend to trap air bubbles but with some practice and very thin coats you could probably get some good results. There are a bunch of different brands but I usually use loctite.

 

[calipsoii]

Finished another lamplighter this evening, this time with an orange LED. I'm trying a different treatment on this one as well - instead of using hot glue on the business end, I'm going with a clear epoxy. Even with a hard scratch-proof coating over it, the hot glue cures somewhat opaque over a couple day period, so this should hopefully keep everything nice and clear for a long time.

First up: a comparison pic of the three I've completed so far!

And next, a little shot to show you what they look like on my bedside table. I've thrown a couple lights with trits in there for good measure.

That's it for pictures right now. I'm currently working out a graceful way to remove the batteries. It's possible right now, but it's somewhat... violent.

More to come!

 

[AnAppleSnail]

That's it for pictures right now. I'm currently working out a graceful way to remove the batteries. It's possible right now, but it's somewhat... violent.

More to come!

This seems like an ideal place for 2 ultracapacitors in series for 5v, and a mini USB socket with a 20 ohm resistor. Plug your keys in once every few weeks and they'll glow forever...

Call it "NiteLight for Life" and you've got a winner.

Edit: Further, it turns out that using 2 2.5v ultracapacitors as described gives you about half as many mW-weeks as you had farads of capacitance.

 

[sunny_nites]

Looking good!

 

[Everett]

I used 100k ohm resistors for both. At first I couldn't even tell if the LED was lit, but it's more than enough light at night.

With a sense resistor this high, your constant current supply isn't doing much. You'll likely get results that are just as good if you simply drive the LED through the 100k resistor alone and save yourself the space and trouble of building the whole circuit. With a green LED and 4 alkaline cells, you'd get (1.5V*4-3V)/100000ohms = 30uA, which is a theoretical runtime of 42 days with your 30mAh cells (likely longer due to voltage droop). With your constant current supply, it's impossible for the drain to be any higher than that 30uA, so if 42 days is enough, I'd go with just the resistor.

 

[sunny_nites]

Good point, Everett.

Since calipsoii got me thinking about low power LED drivers I've been playing around with constant current circuits and resistors as well. In my experiments I found that with the high value of the sense resistor, the traditional 100k bias resistor would not work and you ended up driving the LED with what ever value the sense resistor gives you. But with the right combination of resistors (I used 330k bias and 33k sense resistors), I'm able to run my LED with 20 micro amps from 9 to about 4 volts. Drops under 20 micro amps with less than about 3.6 volts but still bright enough to be useful.

Changing the voltage across the circuit is an easy way to tell if your circuit is actually working or not. If it is maintaining a constant current, the draw will stay approximately the same at 9, 6 or 4.5 volts. If the current draw changes with the voltage by a proportional degree, the circuit is not really working and you are just using the drop across the sense resistor.

Using a resistor is vastly simpler but you would get variable brightness as the batteries fade. Although over the time frame for use (with LR44s with 200mah capacity, should run well over a year), not sure if you would really notice it.

This is the first circuit I've built and etched in about 20 years and the first time I've built one from scratch with surface mount devices and that has really been fun. So, you do get some payback from the satisfaction of getting something that tiny to work the way you want it to.

 

[mcmc]

Calipsoli, these look awesome! I'd be in for like five =)

Interesting thing, is that I have a NiteIze little tiny button cell light intended for zippers. I forget the name. I had it on my First Aid bag on a camping trip and forgot to turn it off. On fresh cells it's pretty bright, but it was dim and I figured the batteries were dead. Well, like 5 weeks later, lo and behold, the First Aid bag was in my truck, at night, and the darn led was still glowing! Very visible in nighttime. I hadn't actually turned it off (has this little turny knob), and I guess it was on the whole time. Amazing.

So it's neat that a couple days later I stumble across this thread with a similar idea!! =D