driver for a xpg r5 emitter

looking for a small driver (16-17mm) to fit in a keychain host. I currently have direct drive and the current sag is killing me. it runs for 30 seconds before i notice a big drop in output off of one imr16340 battery. let me know what you think! would the KD PIN 1845 work? thanks in advance!!

I've heard current can kill, but current sag? (See my tagline link.)

:laughing: sorry, I think the term I was going for was voltage sag. I am still kinda new at this.

Here is your huckleberry http://www.shiningbeam.com/servlet/the-133/**NEW**-3-dsh-Mode-Regulated-Circuit/Detail

Happy Mods!

If you are suffering from voltage sag when driving an XP-G with an IMR16340, then I would suspect that your circuit has an excessive parasitic resistance problem. Otherwise, the nominally 3.7V that the IMR can deliver is more than enough to run an XP-G at full power (and beyond). Even at 1500mA drive current, an XP-G's Vf should be only about 3.5V.

Thus, no buck or LDO regulator driver is going to help until you solve the problem causing your voltage drop in direct drive. The Shiningbeam 7135-based driver most likely will not run at full power because the voltage drop you are suffering in direct drive will result in a Vbatt well below what that driver needs to run in regulation.

A boost driver could work, but again, you really should address the apparent parasitic resistance problem first.

oldspice10 said:

it runs for 30 seconds before i notice a big drop in output off of one imr16340 battery.

Click to expand...

Is your IMR fully charged, ≈4.2 volts? Do you notice a color shift towards blue as the output drops?

Fulgeo said:

Here is your huckleberry http://www.shiningbeam.com/servlet/the-133/**NEW**-3-dsh-Mode-Regulated-Circuit/Detail

Happy Mods!

Click to expand...

I have a couple of those drivers on the way, along with the XP-G R4 that SB is selling.

Sag is odd, I've pulled more than 3 amps from one of those before. 1.5 should be fine.

Black Rose said:

I have a couple of those drivers on the way, along with the XP-G R4 that SB is selling.

Click to expand...

Let us know how good they are, when you get them. I'm interested in buying a few.

~Brian

oldspice10 said:

I currently have direct drive and the current sag is killing me. it runs for 30 seconds before i notice a big drop in output off of one imr16340 battery.

Click to expand...

The issue may not be power in. The symptom is output drop and power is only one of the things that might be causing it. Al hinted at it but the issue could be a thermal. Even if you don't see it turning blue before you turn it off a poor thermal path could be producing a noticeable output drop. The light could even still be cool since the heat isn't flowing out to the body where you feel it.

I am not sure what the issue is, could parasitic resistance be result of poor connection between threads on the body/head and tailcap? seems like this set up should be pulling much more current...then again it could also be a false reading from my DMM. I will look into the possibility of a poor connection, or parasitic resistance. Thanks for all the replies!

I think it might be a heat issue !

From past exp , I have noticed a serious drop in output as the LED heats up over a certain current level ..

To much current , and the LED overheats , and performance drops quickly .

One of my R5's when fed about 1.4A just cooked , but when you limited the current to say 1.2A it ran just fine ...

What current is it doing ? Shiningbeam has a new 1.4A 3 mode driver , + there are plenty of 1.4 / 1.2A single mode drivers out there ...

Check out DX ....

bstrickler said:

Let us know how good they are, when you get them. I'm interested in buying a few.

~Brian

Click to expand...

I posted my impressions and readings in this thread:
https://www.candlepowerforums.com/threads/270128

For a single cell (3.7v protected) you need a buck boost driver, otherwise the output is going to drop considerably as voltage decreases.

Personally, my favorite driver is the gd1000 (from the sandwich shoppe). You can add a 0.1 ohm resister to make it output 1500ma.

Runtime isn't going to be fantastic, but at least you will get full output until the cell is depleted.

well, the emitter is working just fine (I think) it is still very bright, but a tailcap reading off a fresh IMR16340 is about .49A. this cant be the case. It is very bright, the heat doesn't seem to be an issue, it gets warm, but not hot. Output drops noticeably after about 5 min. I ordered more of the host flashlights to make more of these for friends and parents, so I will try with one of shiningbeam's drivers (ordered 4 yesterday!) and fresh emitters. We shall see...should I try this with the less expensive R4's or will the output be noticeably less than my current R5? Thank you all for the excellent help, this is fantastic.

:thumbsup:

I received my order from ShiningBeam, and installed the 3 mode driver to the light. It works flawlessly, and output is alittle higher, however I am still getting the .46 - .49A output, I think there is a problem with the DMM, not the light at this point. Maybe the included wires are too thin to get an accurate reading? anyways, thank you all for the tips about SB's drivers, I ordered a bunch more, with some P7 drivers and XP-G R4's too!
:sigh: this addiction never ends does it?

This 17mm boost board claims a max output of 3A, adjustable by onboard pot:

http://www.dealextreme.com/details.dx/sku.7882

I'm thinking of trying it after I chase down how to bypass all those modes and mode groups.

Techjunkie said:

This 17mm boost board claims a max output of 3A, adjustable by onboard pot:

http://www.dealextreme.com/details.dx/sku.7882

Click to expand...

You'll be disappointed if you really expect 3 A output. It will suck 3 A from a single AA if you turn it right up, but that's input current. The 3 A output figure may have come from using it with a Li-ion cell, in which case it would have been direct drive.

TorchBoy said:

You'll be disappointed if you really expect 3 A output. It will suck 3 A from a single AA if you turn it right up, but that's input current. The 3 A output figure may have come from using it with a Li-ion cell, in which case it would have been direct drive.

Click to expand...

I wasn't expecting 3A output, that'd cook an XPG. What I meant was this board can boost output from a single Li-Ion and maintain 1.5A to the XPG for the entire discharge instead of current dropping as Vbatt drops as with non-boost 1 cell "drivers".

Vf of an XP-G at 1.5 A is what? 3.55V? Using a Li-ion cell - starting at 4.2 V - through a boost driver would just give direct drive with basically no current limiting. I honestly wouldn't like to try it. Those 4x AMC7135 drivers seem much more sensible to me.