Modded Keychain Light

[sunny_nites]

I had one of these solar rechargeable key chain lights and have to admit, it worked surprisingly well right out of the box.

It was powered by a 3.6V, 80mah LiOn battery and as long as I fed it some sunlight or room light once in a while it was pretty reliable.

The main issues I had with it were that it had a two stage circuit that either turned on the two outside while LEDs or the one inside 405nm UV LED (in a two step sequence, from off to UV to white and back off). Neither the white nor the UV lights were terribly bright and there was no way, other than pulling the case apart and hooking a DVM to the battery, to determine the charge status of the cell.

I really liked the size of the light but of course wanted it to be brighter and have a bigger battery. And so on to the build.

I thought about using the two stage circuit that came with the light but really just wanted to have three white LEDs running at a moderate level. This light is for keychain duty after all. So, I went with a single stage circuit from a DX 6V (dual 2016 lithium coin cells) keychain light. I removed the metal “clicker” switch that came with the circuit and wired up the momentary switch that came with the solar light.

I pulled the circuit in the picture from another light I had built previously that was running at a much higher current, hence the P-type mossfet and SMD resistors. I am just running the light at 60 mah (approx 20mah to each LED) and the mosfet was totally unnecessary but would have been more work to remove it than to just run as is. Using a simple 15ohm resistor to limit the current.

The LEDs are 5mm Crees, very generously provided by another CPF member. Each light is running well within its operational limits so they should last a long time. The three Crees produce a nice, warm light that is much brighter than any other three, 5MM LED light I’ve seen so far.

The coin cell was replaced with a 220mah Lipo. I had originally planned building an onboard battery charger with a USB micro connector and the 3.5mm DC jack was supposed to be temporary but after using the light daily for about 4 months now I’m just going to keep it as is. I can keep an eye on the battery via the jack and at the low current consumption, I really don’t have to charge it up very often. The port cover is a fibre optic cable end protector. That was supposed to be temporary as well and I was going to mold up a silicone GID cover but the fibre protector fits perfectly so it will probably stay as is too.

The silicon solar cell had to go to provide room for the Lipo. I used polyester resin as the replacement and the original cover was translucent to allow the charge indicator light for the never installed Lipo charger to shine through. It really wasn’t esthetically appealing though without the charger, really didn’t’ serve a purpose. I replaced it with a GID cover. I like the way it looks much better and the GID could possibly help me find it if dropped in the dark.

GID and non-GID.

The light when in use will charge the GID as well.

Although rare, the light did occasionally turn in my pocket with the original switch cover. The quick fix was to just remove the cover. The recess on the switch has completely fixed the issue. There was a sizeable gap between the switch and the sides of the case without the cover. Fixed that with some black “liquid electrical tape”. I have an idea for a silicone GID switch cover that I am working on. I think the “give” in the silicone might be enough to allow the use of the cover but not allow accidental turn ons.

"Finished" build.

Thanks for looking.

 

[The_bad_Frag]

Nice! :)

Where did you get that lipo?

 

[sunny_nites]

Thanks!

I usually get my lipos from something I've taken apart for parts.

This 220mah lipo came from:

It's not a bad rechargeable light itself but it does have some limitations. Primarily, it has a single LED that is extremely dim. I have several of these and have replaced the LED with a better one and reduced the current limiting resistor from 50ohms to 10ohms and have had good results. I also have a couple that I have added a cree XPG and an aspheric that work pretty well.

The other problem, that keeps me from using it as a keychain or EDC pocket light, is the switch sitting on top of the unit makes it way to easy to accidentally turn on in your pocket. I do use one of the XPG aspherics on my name badge lanyard and haven't had any problems with accidental turn ons in that configuration.

I got these from close outs at a couple of local Radioshacks. I do see them on Ebay from time to time as well.

 

[potpot]

Nice mod! Nothing much left though from the original light except mostly for the housing. :D

I'm also interested on the green key fob, could you give more details on that?

 

[sunny_nites]

Lol, good point! The case was really what I was after. It is really flat and totally disappears in my pocket, yet has enough room for some current and future mods.

I have to give calipsoii and his "Lamplighter Project" for the idea behind the keyfob beacon.

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. 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.

Most of the time I spent on the project was looking for the "right" LEDs. 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 the odd looking 5mm (clear or colored, didn't seem to make much of a difference) units with the dimple in the top. Not sure what these are officially called but I've seen them used in a lot of Christmas lighting. The point on the inside of the dome actually does all the work and it makes the lights much brighter than they should be. Also, the color made a huge difference. Green and Blue were the clear winners.

 

[VegasF6]

They call them inverted cone leds. Mine are all salvaged from Christmas lights too, but you can buy them individually. I really like your keychain beacon. I would ask you if I could steal the idea, but you kind of borrowed it yourself :)
Either way, it's going on my to-do list somewhere.

 

[legtu]

sorry to bring your thread to a tangent. :D imo, your key fob deserves it's very own thread. :naughty:

the beacon light looks like it could be a good addition to your modded keychain light.

as for the led's, they remind me of the lux 1 side-emitters.

 

[sunny_nites]

Good points; this thread is kind of a smorgasboard of projects :oops:

For sure, I can't claim credit for thinking up the beacon lights, this is just my spin on them.

This version is pretty simple to make. Probably the hardest part is creating the circular circuit board. I just go a hold of some round metal punchs and so far they show promise.

I'll post a picture of the next board I put together. It is really simple with only one SMD resistor, two holes for the LED and the battery clamp. I just used a dremel to make the two cuts rather than etching them.

Thanks for the name of the LED. Makes sense since the most prominent feature is of course the inverted cone. Now is a good time to stock up, I've found them in stores priced at $6.00 for 70 LEDs. Probably be even cheaper after Dec 26th.

The one without the case is pretty neat. You can change between red and green by reversing the polarity of the battery.

 

[beach honda]

subscribed for info on beacon lights!

p.s. sweet mod!!

 

[sunny_nites]

Hey guys, I took legtus advice and created a separate post under "Beacon Light".

All future posts concerning the beacons will be updated there, thanks!

 

[sunny_nites]

Came up with an easier and less expensive way to build these little beacon lights.

Single CR2032 battery.

Dual CR1220s

The lithium batteries aren't really any cheaper than the LR types but they allowed a much easier build. I realized that the batteries are the most expensive components and came to the conclusion that with 1 year plus run times it would be easier to just build a new potted unit rather than machining a housing that a user could change the batteries in.

These are also water proof and extremely reliable.

 

[FRITZHID]

Came up with an easier and less expensive way to build these little beacon lights.

Single CR2032 battery.

Dual CR1220s

The lithium batteries aren't really any cheaper than the LR types but they allowed a much easier build. I realized that the batteries are the most expensive components and came to the conclusion that with 1 year plus run times it would be easier to just build a new potted unit rather than machining a housing that a user could change the batteries in.

These are also water proof and extremely reliable.

Details??? Or Link to them? :D

 

[sunny_nites]

I had created another link "Beacon lights" to split the subject out from the modded keychain light post but there wasn't much traffic or interest, so I just posted the update here for the guys that said they were interested in following the project.

I'll get a build shot up but basically the lights use a 220k ohm resistor, one or two lithium primary button cells, clear heat shrink tubing to hold pressure on the wires, are potted with clear polyester resin and run at approx 10micro amps.

The smaller light used two CR1220s but I think there is enough room to switch to two CR1225s for longer run time.

 

[sunny_nites]

Assembled components ready to be embedded: green inverted cone LED, 220k resister, two CR1220 batteries and clear heat shrink tubing.

Almost forgot to mention one crucial crucial component. It's kind of hard to see but there is a piece of clear tape over the end of the inverted cone. You need to keep an air gap between the cone and the resin, otherwise the resin will fill in the space and cone disappears along with its point of light.

 

[kland1234]

Cute, gotta give it a try, what have you used for the molds for the resin? Or do you mold a block and then cut and polish to size?

 

[sunny_nites]

It's a generic resin mold multi pack, like this one:

http://www.amazon.com/dp/B00114OTXI/?tag=cpf0b6-20