First Build: Need HELP matching drivers & batteries to the LED

[365nm]

600-700ma at 4-4.5v

The sku3256 according to DX:

"Accepts 3.6~16V input voltage, needs to be 0.5~0.9V higher than total LED Vf,"
​

so I would need at least a 4.1~4.5v source. at 700ma, that leaves me 3AA alkalines, or 4AA NIMH.

Everything looked good until I found that. I like that the sku3256 is customizable and you can't beat the price if you want 4 of them. Quick calculations show I need a 0.39- 0.42 ohm resistor replacement to get 650-700ma. .39 =~ 650ma. Still looking for a good source - not something most people have laying around.

I am beginning to realize that I'll need 4 AA NIHM or a boost driver.
I'm trying to focus on a driver that will deliver 600-700ma at 4-4.5v

If I go the boots route, I'm looking at this 128086 but I am not sure if it will give 4+ volts. If this works with 2AA I can call it a day and start looking for a 2AA shell.

 

[kosPap]

Re: 600-700ma at 4-4.5v

Now that yuo lnow what the DX3256 looks like you can go to Fasttech and buy the driver from there AND an assortment of SMD resistors

BTW 3xAA alkalines will not be helpful. They wil suffer voltage drop and they will be lower than your needed voltage

 

[365nm]

Thanks I should have checked Fasttech first! Anyone need 99 0.39 ohm resistors?

by DX3256 I assume you are referring to the AX2002 buck driver.

I would still to have to find a housing that holds 4AA NIMH. Any suggestions?

 

[bshanahan14rulz]

Often, zoomable lights will take 1xAA. Some take 3xAAA or 1x18650. Because of this, you may want to go with 18650 unless you can find another zoomable light with the battery configuration you are looking for. If you have other Li Ion lights, then go for it, but if this will be your first, you may want to think long and hard about whether you want to learn about a new battery chemistry or go with a bulkier host and not worry about your batteries as much.

 

[365nm]

Thanks. if I do use a 18650, I'll need a boost driver since one does not meet the voltage requirements and two would waste too much in bucking. I've gone overboard ordering cheap flashlights on ebay, so I'll have a range of options. even though I don't know the exact diameter of the existing drivers, I'll be ordering a boost driver and a standard 700ma buck driver to use in an existing flashlight today.

The time for research is over: I've reached ACTION potential. Ready, Aim..... :thumbsup:

 

[365nm]

Revolvr:

I wanted to report back on my eBay UV LED purchase.

I got a Canadian $5 bill from a travel agency.
I hooked up the LED to a heatsink & good power supply.
I looked for the UV marking as shown on this DIYphysics blog.

I could see the marking shown on the 365nm picture. I have not tested with my cheaper 395nm flashlight yet.
So... I believe this is at least a 3W LED with a wavelength less than 395nm. I don't know of any LEDs produced with wavelengths between these two.

Seller: 2012topdeal

 

[Revolvr]

Revolvr:

I wanted to report back on my eBay UV LED purchase.

I got a Canadian $5 bill from a travel agency.
I hooked up the LED to a heatsink & good power supply.
I looked for the UV marking as shown on this DIYphysics blog.

I could see the marking shown on the 365nm picture. I have not tested with my cheaper 395nm flashlight yet.
So... I believe this is at least a 3W LED with a wavelength less than 395nm. I don't know of any LEDs produced with wavelengths between these two.

Seller: 2012topdeal

Thanks for the feedback. I might give one a try. Did you decide on a driver and host?

BTW, like the idea of testing these with currency. I have quite a few bills from several countries I could try. But I need to catch me a scorpion.

 

[365nm]

Thanks for the feedback. I might give one a try. Did you decide on a driver and host?

I ended up getting a range of cheap flashlights from eBay. all < $5.

I got three drivers:

• direct drive with low voltage protection for lithium. SKU: 1114500
• basic 2x amc7135 (700ma) SKU: 1122403
• boost. (only 550ma though) SKU: 1124802

The problem I didn't forsee was the size of the drivers. I figured they were standard, but there are a dozen different standards from 8mm to 22mm. :duh2: Now I am stuck trying to fit a 17mm driver into a 22ish mm hole. (suggestions welcome) I was looking for 22mm o.d. washer as a quick fix. The LED I tested never took more than 4.1 volts to get to 700ma, and did work at less than 3.5v without significant loss of brightness. So I can use the direct driver, best for single 18650, or the 700ma constant current driver for any source over 4v. I just have to find a way to put it all together.

 

[bshanahan14rulz]

If the lights you bought already have the right sized driver, just use those as contact boards, wrap the driver in kapton or other insulating tape, and just use the original flashlight driver as a contact board by finding the right pads to solder wires to feed the real driver. Just knock off the components with pliers, or use it as practice desoldering.

 

[365nm]

Huh - never thought of that! If there is enough room, it should work.

Thanks!

 

[Revolvr]

I ended up getting a range of cheap flashlights from eBay. all < $5.

I got three drivers:

• direct drive with low voltage protection for lithium. SKU: 1114500
• basic 2x amc7135 (700ma) SKU: 1122403
• boost. (only 550ma though) SKU: 1124802

The problem I didn't forsee was the size of the drivers. I figured they were standard, but there are a dozen different standards from 8mm to 22mm. :duh2: Now I am stuck trying to fit a 17mm driver into a 22ish mm hole. (suggestions welcome) I was looking for 22mm o.d. washer as a quick fix. The LED I tested never took more than 4.1 volts to get to 700ma, and did work at less than 3.5v without significant loss of brightness. So I can use the direct driver, best for single 18650, or the 700ma constant current driver for any source over 4v. I just have to find a way to put it all together.

One host that might work well is the Dorcy 41-4750. This is a yellow plastic flashlight I've seen on Amazon for around $15. It uses a Cree XR-E on a 20mm star at a nominal 700mA, and 4 AA batteries.

The good thing about it is that there is lots of room behind the LED for a circuit board or two. The flashlight actually uses a simple 2.2 Ohm resistor as a driver. This gives about 850mA on fully charged AA batteries, but drops to less than 300mA at 4V. You could remove the LED and replace it with yours, and replace the resistor with a real driver. There's probably enough room for an adjustable voltage boost driver like

http://www.fasttech.com/p/1219203

Where you could fine tune the output voltage to get the current you need from the LED.

The basic basic 2x amc7135 would work as long as the battery voltage was above the LED forward voltage.

Just an idea.

 

[365nm]

I like the driver, but it's not constant current. Maybe 'll order one for another project. I am not sure how it would behave as the input voltage varies . It would probably be just fine. It would take me another few weeks of waiting though, so I think I'll try bshanahan14rulz's suggestion of piggybacking my driver first. then I can use what I already have, no waiting, and I'll have zoom too.

The hard part is getting the existing driver out to work on it, and getting the existing LED out. They seem to be wedged in there pretty good. I'll post pics when I get it done - Perhaps with a list of things I learned to help beat a path for others.
:huh:

 

[365nm]

OK, I wrote it up here

Thanks for your help!