The Greenlite

[jrmcferren]

Okay I was goofing around with some LEDs and a Minimag. I found that you can run a green LED direct drive off of a Minimag though current goes to about 70ma on fresh alkaline cells the current on NiMh (Hybrid setting for a few weeks) is only about 45ma. While still overdriven 45ma is not too bad as the LED is replacable. Current on freshly charged cells tops out at about 57ma but drops quickly. The Greenlite is not designed to be bright, it is designed to provide a low level of illumination where needed in a potential emergency situation. Here are the materials you need for the Greenlite:

-1 MiniMag 2 AA Incan
-1 5mm green LED
-2 AA NiMh Cells

Construction:
-Take the green LED out of its packaging
-Remove the reflector from the MiniMag Head
-Drill the hole in the reflector to allow the 5mm green LED to pass freely.
-Insert 2AA NiMh Cells
-Remove Incan bulb
-Insert LED into lampholder, if LED does not light, reverse LED leads
-Remove LED and trim to length (this may take a few tries)
-Insert LED into lampholder, make sure polarity is correct and LED lights
-reassemble head and screw onto minimag, it should not twist the LED, the LED should turn off when the head is tight

The Theory of operation on the Greenlite is very simple. The NiMh Cells output approx 2.4 volts total (about 2.8 when freshly charged). The LED has a voltage drop of 2.0 volts, leaving 0.4 volts or 0.8 volts left over. The voltage drop of the LED in conjuntion with circuit resistance brings the current level down. Alkalines cells can be used if they are partially discharged first or are only used intermittently. It is easy to tell when a green LED is getting hot as the color will shift to yellow as the diode case gets hot.

 

[StarHalo]

Or you could just use a greed LED Minimag drop-in: http://www.batteryjunction.com/grledmikitwi.html

 

[kramer5150]

... Or a green lens filter combined with a low current drop in.

 

[Jarl]

Or you could congratulate someone on thinking outside the box and coming up with a useful and dirt cheap idea

 

[kramer5150]

Or you could congratulate someone on thinking outside the box and coming up with a useful and dirt cheap idea

Thumbs up for that!!:twothumbs

 

[DUQ]

jrmcferren: thanks for reminding me that I have some green 5mm LED's waiting to be used. I've built a similar light with a white LED. Very simple and straight forward. I think it may have been my first mod

 

[jrmcferren]

Edited first post with updates.

 

[jrmcferren]

jrmcferren: thanks for reminding me that I have some green 5mm LED's waiting to be used. I've built a similar light with a white LED. Very simple and straight forward. I think it may have been my first mod

I'd hold off on that until I finish some testing, I have no idea of LED longevity. If you build it right now, I suggest operating the light no more than a minute or two at a time until the voltage on the cells drops. Once I get back from my second round of schooling and I get a job I may due some more experiments with a breadboard and see if I can get the current down by using different battery types. This whole thing started out as an experiment with LEDs in a Minimag socket, then I was able to get a second minimag to do the actual mod to. The name Greenlite came from a few things. First the color of the LED is green, second in order to prevent extremely high currents you have to use NiMh cells, Third, the current is very low (for the cells) regardless of the overdrive level, forth the spelling lite comes from the fact that it is made from a Mini Maglite.

 

[jugg2]

Hmm, I will go by radioshack and pick up a few 5mm to mess around with. This sounds like a good use for my unused minimag!

 

[angelofwar]

Yeah, I was looking at something like this a few days ago. I guess to get the LED to fit, you need to use a 1/4" bit to bore the reflector out? I've done this with several of mine (I bought 4 mixed bags of LED's at RS for stuff just like this), and to teach my son some electronic basics...great idea!

 

[jrmcferren]

Yeah, I was looking at something like this a few days ago. I guess to get the LED to fit, you need to use a 1/4" bit to bore the reflector out? I've done this with several of mine (I bought 4 mixed bags of LED's at RS for stuff just like this), and to teach my son some electronic basics...great idea!

I just shaved the hole away with my pocket knife, I suggested a drill to make things easier. The more I think about the theory of operation, the more I realize that the LED itself is the current limiting resistor which explains why the LED gets hot, but it was just a little project for me to seek out a curiosity. Remember to use a Green LED, IR, Red, Amber, Yellow, and Orange have the forward voltage too low for this, while Blue, White, Violet, and UV have forward voltages too high to be used.

 

[jrmcferren]

Bump!

 

[Holepuncher]

Remember to use a Green LED, IR, Red, Amber, Yellow, and Orange have the forward voltage too low for this, while Blue, White, Violet, and UV have forward voltages too high to be used.

Actually this works with a 5mm white LED. I did it a couple of years ago. You will get about 10 ma into the led with fresh alkalines. Its actually bright enough to see around the house in total darkness but I keep it on my workbench as a sort of penlight. Battery life is incredible. Still has the same batterys.

 

[jrmcferren]

Actually this works with a 5mm white LED. I did it a couple of years ago. You will get about 10 ma into the led with fresh alkalines. Its actually bright enough to see around the house in total darkness but I keep it on my workbench as a sort of penlight. Battery life is incredible. Still has the same batterys.

Hmm, I may need to get a white and try it, have you tried NiMh cells to see if it works on those?

 

[Holepuncher]

Hmm, I may need to get a white and try it, have you tried NiMh cells to see if it works on those?

I have not tried it with NIMH but I will. My guess is that it will either not light at all or just barely if it does.

 

[Holepuncher]

OK I tried it with NIMH. I get about 2 ma into the LED. Barely useable light output in total darkness. The 5mm I am using is Cree C503B-WAN-CCACB231 and rated 28,000 mcd and 3.2v at 20 ma. Two fresh alkalines will give almost 3.2v.

jrmcferren: If you want PM me a ship address and I'll drop a couple of those Cree 5mm in an envelope on Monday IF YOU LIVE IN THE US. I think I still have about 8 of those.

 

[jrmcferren]

Thanks for the info, PM has been sent.

 

[jrmcferren]

I have accepted Holepuncher's offer and I will post updates to the mod when I get the LEDs. I still feel that the name Greenlite is still appropriate due to the low power consumption. This update will allow for continuous operation due to being operated below rated current. This may allow for limited use in Candle mode as well, meaning you will retain full funtionality of the Minimag.

SUPER IMPORTANT EDIT!:
I will NOT be able to take full or possibly any credit for this mod after this update is complete. For those that have read prior to this edit, I'm sorry if I left any impression otherwise.