What LED and Regulator?

[Shsesc]

Hi, I'm new here. I'm looking to mod a light and long story short, I need a regulator/downconverter and help picking an LED.

The knowns are...
The input voltage will be 7.2-8.4 from 4 protected 18650s 2 parallel pairs in series, is my math right?

There will be room to add my own regulator circuit in the space of the third D Cell.

I want at least 250 lumens I don't know if I'll get it, but that's what I want.

It's going into a 3D Maglite body, it's going to be a car light so size is not an issue.

I have basic tools to work with.


The unknowns are...plenty!...
What LED should I use?

Is there a regulator I should be using or should I make my own? I know depending on the LED I'll have the current output determined for me.

If I make my own regulator where do I go for schematics? I'm handy with a soldering iron and I know some electrickery, but I want a starting point.

What optics and reflectors would make the best light for throw? I have a low powered headlamp for up close stuff.


Is there anything else I should know? If you need more info please ask.

Also, I want to thank you all not only for the help I'm asking for but for everything I've read while I was a lurker.

 

[Shsesc]

I'm now thinking that I'd like more lumens, maybe use a Seoul p7, and instead of 2x2 14500 2x4 14500 using something like an aventrade. Now I'm still stuck on the driver circuit...

Thanks again for all the info here.

 

[Shsesc]

Once I decided on the p7 my searches were more fruitful and I found this... http://www.candlepowerforums.com/vb/showthread.php?t=195358&page=8
I'm going to try the first driver described, I'll have to modify the aventrades I ordered so that they run in parallel with each other. I'm using a 2D instead of 3 as I had planned.

I setup the wires as in... http://www.candlepowerforums.com/vb/showthread.php?t=167866

I'm waiting for the components to arrive. I'll keep you all posted.

 

[Shsesc]

... I'll have to modify the aventrades I ordered so that they run in parallel with each other. I'm using a 2D instead of 3 as I had planned....

What if I used a 7805 voltage regulator or similar to provide the 5V for the 16 mode driver? That way I would be able to run 2x4 14500s in series (7.2-8.4V) as I originally intended with the 18650s.

If I ever needed to I could use 8 NiMH AA cells in a custom holder that puts them in series for 8.4V.

Will the 7805 work with ~8.4 input and/or is there something better?

:poke:

 

[VegasF6]

What if I used a 7805 voltage regulator or similar to provide the 5V for the 16 mode driver? That way I would be able to run 2x4 14500s in series (7.2-8.4V) as I originally intended with the 18650s.

If I ever needed to I could use 8 NiMH AA cells in a custom holder that puts them in series for 8.4V.

Will the 7805 work with ~8.4 input and/or is there something better?

:poke:

Are you talking about this, the national lm78m5?
http://www.national.com/mpf/LM/LM78M05.html
The specs I see say output only 500ma.
If you are trying to drive the P7 I am sure you will want higher driver currents than that.
To the best of my knowledge, and I could be wrong, but I am pretty sure the LM series regulators and most any other 3 pin voltage regulator will waste a significent amount of energy as heat. They are not a switch mode power supply. It sounds like a somewhat clumsy solution.

From your link I am not quite sure which driver you are talking about. The amc7135 sandwich?

I am all for original designs, but, there are already tried and true options for running your P7. You could use 3 nimh cells direct drive. Perhaps 3C or 3D. You could use 4 nimh and a resistor or a linear regulator like the amc7135 found in the thread you linked.

If you prefer lithium you could use 1 cell, perhaps an 18650, or the larger C or D size. (I forget the exact size, 25500 for C, D is 33something.)

Or, if you did choose 2 lithium you would need a good buck converter, one option is the Der Wichtel driver sold here, or the shark buck from the sandwich shoppe. There is a KD buck driver but I won't really recomend that.

1 18650 has a higher capacity on it's own than 2 14500 parallel, so I am not sure what you are trying to acclompish with that setup.

You didn't actually say what your host light will be, I am going to go under the assumption that it is a maglite.

Check this thread:
http://www.candlepowerforums.com/vb/showthread.php?t=193434
And just do a search for mag p7 and I am sure you will be able to come up with a design you like.

If I got anything wrong here pardon me, but since no one else had answered you yet, this should get you going.

 

[Shsesc]

Thanks for responding.
The host light is a 2 D maglite. I think I will try the sharkbuck, but I can't find anything about the output voltage. Could I use that before the configuration of drivers I was going to use... DX SKU.7612 16-mode Driver connect with DX SKU.1886 4x AMC7135 board from the Netkid post.

I want the modes.

So if I connected the battery leads to the Sharkbuck and the output of the sharkbuck to the Netkid setup, would that work?
What's the output voltage of the Sharkbuck?

 

[VegasF6]

The Shark Buck is a constant current driver, the output voltage will be whatever is needed to drive your led at the current specified. At 2.8 amps on a P7 that could be anywhere from 3.25 - 4 volts. You can adjust the output with a trimpot, or by changing sense resistor. One way would be a rocker or toggle switch on your mag. You could have full power-off-custom power. You can also purchase the Remora board with the Shark Buck to give you a full function mode controller. I am not very familiar with the functions of it, but both the Remora and the Shark Buck are of the highest quality and efficiency out there.

Using it to drive the 7135 solution with mode controller is a novel idea, frankly I don't know what the drawback vs benefits would be. I would be worried about efficiency. But, for 9 dollars more I would stick with the Remora.

I am going to refer you to the Shark Buck thread for answers from people that really know what they are talking about.
http://www.candlepowerforums.com/vb/showthread.php?t=211599

 

[Shsesc]

Project Complete, pictures coming soon

I went with the shark buck and finally got the darn D Li Ion cells from KD after 3 months. The build is complete. Works great on either the above mentioned cells or AA batteries in a 6xaa series modamag gizmo from sandwich shoppe 8xaa in series wouldn't fit. Different springs are required for the different setups.