4xAA DIY, LD41 @ 190Lm=7.5Hours, What Emitter and Driver to do the same?

FireWire

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Hello,

In advance thank you to anyone who wants to help me, it is very kind and gracious of you.

Question
A 4xAA battery, LD41 runninng in the 190 Lumens setting, runs for about 7.5Hours Nimh.

I would like to make a DIY LED torch/flashlight that runs on 4xAA batteries, and gets 7.5 hours with constant current.

What Emitter and Driver do I need to do the same?

Ps. Thank your in advance, i have been trying, and trying to make this DIY myself, but I am not very knowledgable, about pairing an emitter and a driver. I wanted to see if I could make it myself, and learn by making.
 
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DIWdiver

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The Nichia 219B warm white high CRI with D180/sw35 ranking should give you just about 190 lm (at the emitter) at 700 mA with a CCT of 3500K. Any driver with two AMC7135 chips should work pretty well with your batteries and desired output.

There are a ton of other LEDs that would work just fine as well. The Cree XPG2 immediately comes to mind. Like most of the other modern options, it would probably give you more lumens and lower CRI. Also, I think the 219C is available now. Anything rated at 2-5W should be fine. Lower CRI will generally get you more lumens, as will higher CCT. Keep in mind that there are lots of bins and rankings within any product family. There are 219Bs with higher and lower luminous flux, other color temps, and lower CRI.

AMC7135 based drivers come in increments of 350 mA, and they are only adjustable using PWM dimming, which is how the drivers achieve different brightness modes. There are other types of drivers available, including other current levels, but for your setup I think '7135 types are your best bet.
 

FireWire

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Your the best! Thank you for taking the time and effort to help me.

Can I use a XML2 to give a nice wide flood light, using a optical lens?
i found its
OPERATING VOLTAGE2.9-3.5 -volt
Running it on 4xAA that's 4.8 volts in series or 2.4 volts in parallel, could you kindly assist me, what do I do?

here is what I am thinking of:

XML2
https://m.fasttech.com/products/1609/10001903/1136801-cree-xm-l2-t4-7c-2800-3000k-white-led-emitter

DRIVER - CONSTANT CURRENT 7135 type
https://m.fasttech.com/p/1127408

how does that look to you so far

ps thank you in advance
 
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DIWdiver

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You definitely want series connection of the batteries. That will give 4.8V on full charge (actually somewhat over 5V initially, dropping rapidly to around 4.8V). The parallel connection will not give enough voltage to run the light.

The LED and driver you selected should work well together, and with the batteries you intend to use.

The XM-L2, like most high-power LEDs will provide a very wide flood with no optics at all. Shallow reflectors can narrow the beam a little, deep reflectors can narrow it some more, TIR optics are probably a bit better at narrow beams, and aspheric lenses will provide the best performance with narrowest beams.

For what you want, a shallow or medium reflector is probably best.

The driver you linked is a 350 mA driver. You probably want a 700 mA driver to meet your goals.
 
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FireWire

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Hello

Thank you for being so kind as to help me.

Driving at a constant current of 700ma, will I still need a heat sink for the led and driver? I could only find one like this, not to flat though.

HEATSINK
https://m.fasttech.com/p/1349601

Also does a constant current driver, deal with supplying the correct votage, as the votage range of the led may mean it's blown by the 5-4.8 votls.

Thank you in advance
 
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DIWdiver

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The LED will be generating somewhat over a watt of heat. That's pretty easy to deal with, but you do need something of a heatsink. The one you linked is probably okay if it is in free air. If the airflow will be restricted, you probably want something bigger.

The whole point of the constant current driver is that it takes care of the voltage difference between your battery and your LED. This type of driver is basically a variable resistor that's controlled by a circuit that monitors the output current. If the current is too high, it increases the resistance. If it's too low, it decreases the resistance.

You need to make sure the driver input voltage range includes ALL of the battery's voltage range (it does), that the driver's output voltage range includes your LED voltage (it does), and that the current setting or settings meet your goals (it does not).
 

FireWire

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Hello,

you are great at this! Very kind of you take the time to help us in the forum as you do.


I have have seen really nice and flat coin or disc shaped heatsinks on here, I hope to put it in a flashlight one day when it's all setup. I just don't know where to purchase them. Please could you kindly offer me assistance.

Will I need a heatsink for the constant current driver if it goes in a flashlight?


Thank you for your help, you are a really nice person.
 

FREI

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Lets do a little bit math:

If you take eneloops you have round about 2000mAh. If you take a 700mA linear driver you get 2000mAh/700mA= 2,87h runtime. Not what you want.

From the other direktion:

you want 190lm. If this 190lm should be OTF Lumen, you need round about 220 LED lumen (efficiency of lens/optic/reflector). One of the most efficient LED is the xm-l2 U3.
For 220lm the xm-l2 needs 1,173 watts. 1,173Wx7,5h=8,8Wh. 4 eneloop gives you 4x1,2Vx2000mAh=9,6Wh(simplified). If you choose an efficient 400mA buck driver (not linear) it could be possible.
 

DIWdiver

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Lets do a little bit math:

If you take eneloops you have round about 2000mAh. If you take a 700mA linear driver you get 2000mAh/700mA= 2,87h runtime. Not what you want.

From the other direktion:

you want 190lm. If this 190lm should be OTF Lumen, you need round about 220 LED lumen (efficiency of lens/optic/reflector). One of the most efficient LED is the xm-l2 U3.
For 220lm the xm-l2 needs 1,173 watts. 1,173Wx7,5h=8,8Wh. 4 eneloop gives you 4x1,2Vx2000mAh=9,6Wh(simplified). If you choose an efficient 400mA buck driver (not linear) it could be possible.

I don't recall what I was smoking when I calculated that the batteries would be sufficient. I must have calculated based on 3.5 hours, not 7.5 hours.

1.2V is pretty optimistic for an average voltage for NiMH cells. They usually drop pretty quickly to 1.2V, then gradually to 1.0V, at which point they are pretty dead. I usually use 1.1V for this kind of calculation.

EDIT: Just looked at an Eneloop Pro discharge curve, and at 500mA it looks like 1.2V is actually pessimistic. It appears 1.25V would be better. At least for new cells. END EDIT

On the other hand, there are much higher capacity cells available. I don't know if any of the 3000's are real, but I know Sanyo offers 2700. Even Eneloops are available at 2550.

I had a hard time believing your numbers so I looked up the data sheet (had to download a new one for the U3). I never knew how low the Vf would go at 400 mA. Only 2.75V. Wow!

You might have been more careful than me, I calculated 1.1W for 220 lm (at 25C) That would be 200 lm/W! Even if it's only close to that, that's still impressive.

Of course real world performance won't have the die at 25C, but with way under a watt of heat, there's no reason for it to be anywhere near 85C.
 
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FireWire

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Hello

You both are great, like Flashaholic Jedi Knights!

with this new turn, could you kindly advise me, I canceled my order, now ready to buy a new lots of what you say: :)


which LED to use
which regulator: buck, constant current, etc
which heatsink that can be put in a flashlight (maybe a 2 C - similar to 4AA in size)
are there any links you may know of for the items


thank you in advance Flashaholic Jedi Knights
 
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FireWire

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Thank you!

Your help is greatly appreciated.

I have been looking around, for a 350mA (approx) constant current driver, runs on 4AA, any idea where I could find one?

thank you!
 

scs

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Given the low output and therefore low Vf required, wouldn't a buck driver work even better than a linear driver?
As I understand it, with a linear driver, cell voltage over the required Vf goes unused, so the constant current the driver is delivering is pumping in extra wattage that produces heat, not light.
Would a buck driver substantially reduce this waste of wattage?
 

DIWdiver

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That depends on how well the driver is made. If it's good and pretty efficient, then it could make a substantial improvement.

Simple but well made buck regs should be in the 80-90% efficiency range at these low voltages. More complex ones or at higher voltages they can exceed 95%. At the other hand, I recall reports of some super cheap ones being below 70%.

If you can change the design, you may find some interesting things. For example, it's now feasible to run some designs on 3S NiMH, and a super-cheap linear regulator could achieve average efficiency around 85%.
 

DIWdiver

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The blue wire is marked OUT-. I assume the red wire is marked OUT+, but I can't see it in the pic. If so, red to positive, blue to negative on the LED.

I don't see the back, but normally there's a large center circle for battery+ and the outer ring is battery-.
 

FireWire

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The blue wire is marked OUT-. I assume the red wire is marked OUT+, but I can't see it in the pic. If so, red to positive, blue to negative on the LED.

I don't see the back, but normally there's a large center circle for battery+ and the outer ring is battery-.

:)Thank you:)
On the non-micro chip side of the driver, the side that the battery solders on to, can we solder on it or will the heat destoy it?
 
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DIWdiver

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you can solder on it. It should solder quite easily. MUCH easier than soldering stars.

It IS possible to destroy it this way, but those big areas of copper make it pretty hard to do. It's much easier when soldering itty bitty little pads. Just don't hold the iron on there for more than 5-10 seconds, and you should be fine.

It definitely helps get a good strong bond if you 'tin' the wire first. This means to get the solder to flow on the wire, into the strands, to make a solid mass before soldering it to the board.

If you are having a hard time, let the board cool off and come back later, rather than keeping at it until the thing is ruined. What will happen if you are there too long is the copper will come unglued from the fiberglass. Since you have such a big area of copper, it wouldn't even be a big deal if you did 'lift' a little of it.
 

FireWire

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Hello

Question 1
I am about to solder it, its a tin and i think copper mix solder, is it safe to solder in a sitting room or should i do it out doors?

Question 2
If I drive the XML2 at a constant current at 700mAh, will i need to have a heat sink, other than he mini round one under the LED (I guess its a type of star)?

Question 3
I am going to put it in one of these, if i cut the reflector is there anything toxic in the silvering of the plastic reflector?
http://i.ebayimg.com/00/s/NTAwWDUwMA==/z/f-cAAOSwcwhVQk5W/$_12.JPG

Thank you
 
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