DX DIY Body Shell advice and guidance needed

[Wolf359]

http://www.dealextreme.com/details.dx/sku.15687

i have order this DIY flashlight kit from DX what i want to do is put in a Q5 LED, with an AMC7135 350mA Regulated Circuit Board from DX, to use with a 18650.

i think i would get about 100 lumin with this setup running for about 6+ hours.

would the DX AMC7135 give flat regulation or will it dimm alot as the battery depletes ?

i am looking fo advice and guidance on wether this will work and suggestions from those better versed in DIY. this is my way of dipping my toe into the DIY arena.

thanks for your help

ian

 

[Black Rose]

Is that a new one they just added?

That seems to be the first DIY kit they offer that includes a pill. The other two DIY kits they offer do not include the pill.

 

[Flashfirstask?later]

Yes, this is the only one so far that comes with a pill. DX has said they were going to have pills for the other two either separately or with but that has not happened yet.

The 15687 is really the 12346 but without a driver and emitter.

 

[VegasF6]

Ok, here goes. Standard disclaimer, I am no expert etc.
But, 1st run time is going to vary depending on the forward voltage of your led. No way to know in advance, you will have to test your led with that driver. Used to be Q5's had higher forward voltage than lower series leds. Supposedly that mostly solved? I would imagine you will be well under 3.0 volts at that current, so you should be good.

As I am sure you know, amc7135 is not a boost circuit of any sort, so yes, you will get a linear dimming of your light, not the sudden moon mode of others. However, lithium has a relatively flat discharge curve anyhow, especially at that current level.

Runtime will also depend on your battery quality as well, both the brand, and how many charges and discharges you have had and the quality of your charger too. Over charge, hurt the battery. Under charge even a little and lose run time.

You would think, OK I have an 18650 rated at 2400 mAh, so dived that by 350 to get my runtime. But of course, first many of these batteries are over rated, and probably best you can hope for is 2000 mAh if lucky. Now you are down to about 5.7 hours.

But of course the big problem will be efficiency of the driver it self. When the forward voltage of the led and the battery are at the same level this driver gives very good results, as I recall over 90%. But when your battery voltage is higher, and it certainly will be at around 4.2, the excess voltage is burned off as heat. You can expect significant drops in efficiency then.

I forget the exact #, but at a certain voltage they will drop out of regulation and direct drive.

So, it will certainly work, but I wonder if you would be better served either buying a premade light with modes, or a quality switching regulator. If run time is truly what you are after, and it sounds that way from your drive levels, then efficiency is what you are really after.

For instance, the sandwich shoppe has the GD400 for 18$ which is a buck boost regulator. Problem is it is only 14mm so I am not sure how you would mount it in the ring of that diy kit. Gotta be a way though

 

[TigerhawkT3]

You don't always need a boost circuit to run an XR-E off a Li-Ion - only if the Vf at the current you want is higher than the cell voltage. The output won't dim unless and until Vbatt reaches and drops below the Vf, as the 7135 is a CC LDO regulator. The Vf of an XR-E at 350mA is about 3.1-3.2V, so it should stay in regulation for the entire runtime on a Li-Ion.

You'd probably get 70-80L out the front for 5-6 hours.

 

[Black Rose]

DX has released another DIY kit that includes the pill.

http://www.dealextreme.com/details.dx/sku.15693

I guess it proves they did listen to all the complaints about the missing pills in the first two DIY kits they released.