I know , from reading in the forum, that people reprogram only the 7135s’ drivers.
I am searching for a dual li-ion driver which will be programmable as well, is there any out there?
If not, that possible to take any driver with unknown micro-controller on it, and replace it with ATtiny13A (for example)?
OR in addition does anyone know any other single li-ion driver that works on mosfet and not on 7135, which can be reprogrammed as well?
because all the 105c based drivers are linear, they dont step the voltage down, just pass it straight threw, to run on 2s cells it would output 6v (8.4v) so it could run 1 MT-G2 or 2s XM-L2’s, on 3s cells it would run 3s XM-L2’s but the only way to run a single 3v emitter (XM-L/XP-G) is to run on 4.2v only (1s)
Cereal_killer’s explanation is close, but actually only describes the behavior of an FET driver. I’ll explain about each driver in your list:
MOSFET modded Nanjg 105c work like Cereal_killer described. They do not have current or voltage limiting. They will always allow as much voltage (and current) through as they are able to. 2s will destroy your LED. Dimming is done via PWM and does not reduce instantaneous voltage or current.
The 7135 based (commonly called 105c based) drivers will probably output the correct voltage for a single XM-L2 when run on a 2s Li-Ion battery. The linear driver will produce too much heat. The driver will die. A zener mod will protect the 7135's from getting too high a voltage on the VCC pin, but that mod will not protect them from too much wattage being turned into heat.
The Knucklehead may be an option for you, but you should understand that it is still in testing. So far it's been determined that it *must* be heatsinked when run above approximately 2 amps. We do not yet know exactly how much heatsinking is required. Rufusbduck plans to do more testing on this. DBCstm does already have one working at nearly 4 amps; it is driving an MT-G2 which is a significantly higher Vout than your XM-L2. The lower Vout of an XM-L2 will put more strain on the driver. If you build one of these you will be in experimental territory.
WarHawk-AVG mentioned that I have a buck driver, but it is also experimental and not yet publicly available. Therefore it's not what you want right now. Here is the development thread.
There is good news! Since you have 20mm, you are actually not in bad shape. Can you tell us what host you are using?
The LD-29 may be a good choice for you. HKJ has reviewed 2 variants of the LD-29, but only the one from FastTech is currently available. Here is his review of that one.
wight, Thanks for your great reply , Now I understood all the differences between the drivers.
I need something that I will be able to reprogram, because I’ll add it a hall effect switch (electronic switch), and I want it to work with 1-mode only.
I am using some diving flashlight hosts right now, one of them is TR-J2, another is maxtoch 2*26650, aletocn and non-branded Chinese.
All of them for diving, so heat is not my problem it will be always cooled by the water.
About the LD-29, I have some , and it is nice, as it could be modded to 3.6A with a change of the current resistors, BUT, I couldn’t make it to work with 1-mode only. and I cannot reprogram it to work with an electronic switch.
Is that possible to change the MCU on LD-29? or in any other way, make it 1-mode and add an electronic switch?
And about your buck Driver,it looks amazing, Ill keep watching you posts, maybe your driver will be the one suit my purpose
I do intend to investigate the modding potential for the LD-29. It appears to use a MicroChip PIC controller. I would replace that with what I’m familiar with, an Atmel ATtiny13A. The pins on the PIC need to be scoped and maybe checked with a DMM to find where the (hopefully) PWM comes out and where the voltage divider for LVP is. I have no immediate plan to do this work, but it’s on my to-do list. Figuring that stuff out should make it easy to use a piggyback board or deadbug style wiring and one of the standard e-switch firmwares.
If you truly only wanted 1-mode and were willing to lose LVP (low voltage protection) it might be easy to do with the LD-29. Find the PWM pin and short it to the PIC’s VCC. That should leave the driver on high all the time with no low voltage protection or warning. It would still need a clicky switch though.
PWM probably goes to the MOSFET’s gate. Possibly through a resistor or other component such as a gate driver it may be easier to follow the trace back from the gate pin towards the MCU.- VCC will not come from BAT+ because BAT+ can be higher than the maximum VCC (when used with 2 cells). VCC will come from a voltage regulator. The voltage regulator is probably one of the 5-pin packages you see on the board. You should own a digital multimeter (DMM), if not I recommend you purchase a cheap one. You can use your DMM to verify VCC.
IIRC the markings on the chip are legible - in that case you can just look at the datasheet to figure out where VCC is. Yeah, Microchip PIC 12F683.
On the PIC Vcc is called Vdd and it’s on Pin 1.
EDIT: I had a “blonde moment”. PWM will not go to the MOSFET’s gate. PWM will go to a “buck controller” chip. You still may be able to find the buck controller by following the gate trace back from the MOSFET.