i assembled the drop in yesterday which was a major pain, the thing is i pushed the driver board into the pill and cant get it back out, and only realized this morning that i was driving to 1400ma. it is being driven by 3 AAA and good heatsinking. is the color im getting going to be extra blue or am i going to have severely shortened lifespan?
blue xr-e driven to 1400ma
- Thread starter doctaq
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kramer5150
Flashaholic
If your DC-DC board bucks Vin down sufficiently, you should be just fine with 3xAAA cells. Hot off the charger Eneloops are ~1.35V. So with freshly charged cells your driver will have to buck down a little.
Double check the data sheet on the blue colored XRE. Make sure your driver bucks Vin down enough to avoid over driving the Vf of that LED. I can't recall what the Vf is for the blue XRE.
IIRC the Eneloop AAA starts to sag somewhere shy of ~1A (don't quote me on that... I can't recall specifically). So even though your 4x7135 board is capable of delivering ~1.4A, I speculate that its not going to push too much more than ~1A to the LED.
Make sure you are using an insulator to isolate LED- from the reflector back-side of the pill. If -LED from the DC-DC board is allowed to contact the reflector back-side you will be direct driving the LED. (which actually might not be a bad thing with 3AAA). The 7135 chip behaves much like a direct drive circuit, it only limits Vout to the LED, when Vin>3.6V. Its like a voltage protection circuit for the LED when cells are freshly charged.
I usually like to file down my 17mm boards so they drop easily in/out of the pill. If you have crammed it in there really tight, you can push it back out with an allen key through the LED wire holes.
Good Luck with the DIY... I hope this helps.
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thanks kramer, i ended up poking it back out with some sharp forceps i had, i hadent considered the current limiting nature of the batteries, i still did remove one of those amc7135 boards though. i will certianly note the isolating as i plan to mod up a couple of the 14500 size akoray from dx
