Dorcy Metal Gear Mod?

[IndecisiveFlashaholic]

Im very new to modding, but would a dorcy Metal Gear (which runs off of 3 AAA cells) be able to use either this seoul or cree led? The driving voltage is 3.7 but 3 AAA cells give off 4.5. Please correct me if i am wrong ( I probally am ).

 

[Nitroz]

Im very new to modding, but would a dorcy Metal Gear (which runs off of 3 AAA cells) be able to use either this seoul or cree led? The driving voltage is 3.7 but 3 AAA cells give off 4.5. Please correct me if i am wrong ( I probally am ).

I had great results with the Cree in the Metal Gear. Here's some pictures of the mod.

http://www.candlepowerforums.com/vb/showthread.php?t=144164

 

[IndecisiveFlashaholic]

Thank you very much Nitroz!

 

[Nitroz]

Glad I could help. Good Luck!

 

[needforspeed]

I have done two of them, both with crees and cree optics.

Both rock, nothing but emitter and reflector/optic swap.

One I actually use a single rcr123 3.7v and get excelent output.

They are easy and fun.

Bill
Massachusetts

 

[IndecisiveFlashaholic]

needforspeed- Where were you able to find crees with reflectors?

 

[Nitroz]

I have done two of them, both with crees and cree reflectors.

Both rock, nothing but emitter and reflector/optic swap.

One I actually use a single rcr123 3.7v and get excelent output.

They are easy and fun.

Bill
Massachusetts

Why use the cr123 when you can use one 18650?

 

[ace0001a]

After Nitroz did the one he linked to above for me, I decided to try myself as I've got many Metal Gears to play with. Anyway, I've found that CreeXREs work well in them, albeit I can't say I've ever been a fan of the beam pattern. And if you want to screw the head all the way tight, I've found that you need something like 1 and 1/2 pennies worth of metal to raise the star plate if you're using a CreeXRE star rather than a bare emitter. What does work great and is a simple straight swap out of the star is going with an SSCP4 star. I've done a couple going that route and it works great. No need to raise the emitter or star. Think I'm going to try optics with the Crees next on some other Metal Gears I got...

Oh and someone has already done a CR123 mod here:

http://www.flashlightreviews.com/mods/dorcymg.htm

Anyway, the Metal Gear's a good flashlight to play with. I've been trying to find the right driver to put in one. The plastic chamber behind the star and metal plate affords room for one. I got a real good 700mA converter from Arcmania I haven't gotten around to trying yet, but it's next on my Metal Gear mods list. Happy Flashlighting!! :rock:

 

[IndecisiveFlashaholic]

Can anyone explain why the Seoul and Cree leds are able to run off of 4.5 volts when their driving voltage is only 3.7? I am a beginner to modding/electronic knowledge.

 

[sysadmn]

It's not the voltage that kills the LED, it's the current. Presumably the Metal Gear has either a resistor or a more sophisticated regulator that limits the current.

Put a resistor in series with the LED (connected one-after-the-other). If you have 4.5 volts, and the voltage across the LED is 3.7, the voltage across the resistor will be (4.5 - 3.7) = 0.8 volts. (voltage / current) = resistance. If the LED runs at 350 milliamps (current), then (0.8 / .350 ) = 2.3 ohms.

 

[IndecisiveFlashaholic]

Ok, it does have some type of circutry below the Luxeon emitter so that must be some type of resistor. Thanks for clearing that up sysadmn.

 

[rheslip]

It's not the voltage that kills the LED, it's the current. Presumably the Metal Gear has either a resistor or a more sophisticated regulator that limits the current.

Put a resistor in series with the LED (connected one-after-the-other). If you have 4.5 volts, and the voltage across the LED is 3.7, the voltage across the resistor will be (4.5 - 3.7) = 0.8 volts. (voltage / current) = resistance. If the LED runs at 350 milliamps (current), then (0.8 / .350 ) = 2.3 ohms.

I just modded a similar light (Dealextreme "Raket") with a Cree. I didn't have to raise the led since the head/reflector will screw down over the emitter on this light. The Raket has a 1 ohm dropper for the stock Lux knockoff in it. I bypassed the resistor and got a big increase in output with the Cree. With 3 fresh AAAs its close to 1A which is the limit for the Cree emitter but it quickly drops to about 600ma as the batteries heat up/discharge. AAAs can't sustain that output for long which in this case avoids overdriving the led.

I've tried an 18650 in this light and it WILL sustain 1A or more. A dropping resistor is a good idea in this case to preserve the emitter. The Cree is rated for 1A max but you have to have very good heatsinking. I decided just to stay with the 3 AAAs - still great output.

Rich

 

[ace0001a]

Well when it comes to flashlights that use 3AAA carriers, there is almost always resistance presented by the carrier. Since the Metal Gear has a LuxI 1 Watt LED, they put a 1 ohm resistor on the internal circuit board in the plastic cylinder. If you plan on sticking to AAA batteries, you'll need to remove or bypass the resistor to get it brighter. Also, going with NiMH batteries will give you steadier discharge along with longer single use runtime. For occasional use, I recommend either sticking with Alkaline or the new Rayovac Hybrid NiMH batteries.

 

[IndecisiveFlashaholic]

So removing the resistor would not be a problem if i continue to use alkaline AAA's?

 

[ace0001a]

So removing the resistor would not be a problem if i continue to use alkaline AAA's?

As Sysadmn pointed out, it's not necessarily the voltage that will fry the LED as it would be the current. The facts here are that AAA batteries are low capacity which plays in limiting their ability to deliver a lot of current. Battery carriers will always have some resistance in them. Combine those two facts together and that's why you're able run 3AAA batteries without a resistor on Luxeon III, K2, SSCP4 and CreeXRE LEDs in these kind of flashlights. Part of how I figured this out is that every 3AAA Luxeon III flashlight I've taken apart has no resistor in it, whereas the same (or similar) model with a Luxeon I in it has a reistor. That lead to me swapping them out without a resistor and they've been working great and bright since...

 

[IndecisiveFlashaholic]

Then I think I will have to order a new led for my light. Thanks for the feedback guys!

 

[needforspeed]

IndecisiveFlashaholic- Sorry about my error. I meant to type in Optic but my happy fingers got the best of me and typed in reflector. Original post has be fixed.

Nitroz- I use rcr123's because thats what I have lying around, 18650's would be better, but i don't want to buy them. I'm a little cheap in that respect.

Bill
Massachusetts

 

[IndecisiveFlashaholic]

No problem! Thanks for clearing that up.