These drivers focus on performance. The PWM frequency is over 5KHz so there's absolutely no noticeable flickering. The microprocessor uses "on" time to control mode switching - if you turn it off within 2 seconds since you turned it on, then it will be in the next mode when you turn it on again. If you leave it on for more than 2 seconds, then the next time you turn it on it will stay in the same mode (last mode memory).
Size: 16x6.5mm (L1P size); Diameter can be trimmed down to 14.5mm
Full output: 800mA
Reverse polarity won't fry the board nor the LED. But there's a current draw. So if you've just changed battery and find the light not working, turn it off and check the battery polarity.
a) 4% - 20% - 100% (no strobe)
b) 4% - 20% - 100% - 10Hz Strobe
3.7V Li Ion
Full output: 1A until 90% discharge with a typical Cree and 18650; then gradually goes down until 98% discharge, when output will drop below 2mA and the battery voltage is around 3.1V. Safe to use with unprotected batteries. Full output level can be changed by replacing a resistor on the board.
Reverse polarity protection
a) 1% - 7% - 30% - 100% (no strobe)
b) 1% - 7% - 30% - 100% - 10Hz Strobe
-- 1AA Beam Shots ----------------------------
I modified a DX Elite (Elly with Cree) using one of my boards. Here are some comparison beamshots. The Rex2.0 has the whitest tint and the best beam pattern, while both the Elite and the MK2X are yellowish. Probably due to the difference in tints, in the photo the Rex appears brighter but to my eyes it's the contrary. After 10 minutes on high, Rex got hot but the Elite was just warm, supposedly due to its bigger size.
-- 1AA driver beta batch - July 20 --------------------------------------------------------
Some 1AA boards have been assembled. In 100% mode the board outputs 750mA at an efficiency of 81%. If you use a good switch and a Q2 Cree, don't be surprised to see 1A at the LED at 77% efficiency. StefanFS gets more than 1A with a 18650 sized NiMH. It can light up at 0.75V and outputs 70mA at 86% efficiency. With a 2300mAH battery the runtime (to 50%) is about 40 minutes in 100% mode and 4.5 hours in 15%. I believe this driver is taking the power and efficiency of 1AA booster to a new level. Now you get Li Ion performance with NiMH! Vive la NiMH!
Areas to improve: Compensation needed for the nonlinear relation between PWM percentage and actual output percentage (see beamshots below); efficiency in lower modes can be better; the size can be smaller (15x6.5mm). A friend of mine and I are working on these and will come up with an improved version in a couple months. But I'd like to keep this a hobby and thus can't promise a delivery date.
For those who have been waiting and are interested in trying out the current version, I'm offering a limited quantity at $8 each. No more of this version will be made.
Update: The beta batch was sold out on Aug 2.