46mm - SRK V2 FET + 7135 Driver

46mm - SRK V2 FET + 7135 Driver
Product Code: SRKFETV2-DRVR
Availability: 10
Price: $14.99

Available Options

* SRK V2 Firmware:

* SRK V2 FW Stepdown:

* SRK V2 Input Voltage:

Qty:     - OR -   Add to Wish List
Add to Compare

This is an updated version of the popular SRK FET driver.  This version adds more LED pads, a 7135 option for lower moonlight mode (STAR firmware only), an LDO voltage regulator option for 2S or 3S cell use, support for an external temperature sensor (STAR firmware only) and much more.

This driver will give you near-direct-drive performance in a drop-in package.   Because of the high output potential, this driver should probably not be used with most aluminum MCPCBs, unless it is a light with a lot of emitters.  Check out the current regulated 7135 based SRK driver instead for use with stock or aluminum MCPCBs.

The driver features tabs that will need to be filed down to achieve a tight fit in your host light of choice.  They are necessary due to the slightly different tolerances that exist in these lights. Every driver is tested before being shipped!  It may take 10 days for this item to be built, tested, and shipped.


  • Approximately 46mm diameter (larger with fitment tabs)
  • Fits most SRK style "soup can" lights
  • Low-voltage protection for 1S, 2S, 3S, or 4S cell configurations 
    • Input voltage must closely match output voltage; this is NOT a buck or boost driver
  • An LDO option for use with 2S, 3S, or 4S cell configurations
  • Gives near direct-drive performance (direct-thermal path MCPCB recommended!)
  • 5 LED+ and LED- pads
  • Provisions for an external temperature sensor (currently only compatible with STAR firmware)
  • 7135 for extra-low and efficient moonlight mode (1S and 2S only)
  • Reverse polarity protection

Firmware Options:

There are three great firmware options for this driver:

1. STAR Momentary - No External Temperature Sensor

This firmware provides a simple, yet powerful, user interface.  Starting from off, or any other mode, a short click moves the modes forwards, while a long press moves the modes backwards.  This means that you can start in either the highest, or lowest, mode with either a short click or long press, and then move up or down through the modes at any time.  This firmware also offers an ultra-low moonlight mode, thanks to the secondary output 7135 (1S and 2S only). 

With this option there is also the option for a turbo timer.  The turbo timer will step the light down from the highest level to the next lowest mode at a preset time.  Here are the turbo timer options (STAR Firmware, no temperature sensor only):

  • 30 Seconds
  • 60 Seconds
  • 90 Seconds
  • 120 Seconds
  • 180 Seconds
  • 240 Seconds
  • 360 Seconds

STAR Momentary Mode Options:

  • a. "SRK Special"
    • 7 visually well spaced modes ranging from moonlight to all-out-power
  • b. "Simple"
    • 3 modes: moonlight - 33% - 100%
  • c. "Custom"
    • Choose your own modes.  Here are the options (please enter in checkout comments):
      • Number of modes: Between 1 and 7
      • Mode levels: For example: Moonlight - 5% - 33% - 100%

2. STAR Momentary - External Temperature Sensor

Same user interface and mode level selections as above, but with an external temperature sensor included which steps down modes as the light heats up.  The temperature sensor is set to around 60 degrees celcius, which is about as hot as you typically want a flashlight body to get without burning the user.  It can be affixed to your desired location with an epoxy such as Arctic Alumina or JB Weld (Arctic Alumina is much easier to remove in the future if desired).

The external temperature sensor wiring is as follows:

With pins oriented down, at the 6 o'clock position

  • Left pin: ground (T-)
  • Middle pin: output (tIN)
  • Right pin: VCC (T+)

2. moppydrv (No 7135 or external temperature sensor option)

moppydrv Multi-Group Electronic Switch Firmware Option

This firmware allows the ultimate in user customizability, with 16 built-in mode groups, that the user can select via a series of button presses and a user programmable turbo timer that will automatically step the power down to 50% after the set time is hit (see below for instructions).  On the SRK V2 driver there is no 7135 or external temperature sensor support or 7135 support.


Low voltage protection:  The light will begin to step down output at around 3V/6V/9V/12V (depending on cells used) under load.  The light will not shut completely off, but will continue to run at a moonlight level.  


User Selectable Groups:



  1. 100% Only
  2. 5% - 100% | [100%]
  3. 30% - 100% | [100%]
  4. 70% - 100% | [100%]
  5. 50% - 10% | [100%]
  6. 75% - 20% | [100%]
  7. Moon - 30% - 100% | [100%]
  8. 100% - 30% - Moon | [Strobe]
  9. Moon - 20% - 70% - 100% | [100%]
  10. 100% - 70% - 20% - 0% | [Strobe]
  11. Moon - 5% - 15% - 50% - 70% - 100% | [100%]
  12. 100% - 70% - 50% - 15% - 5% - Moon | [Strobe]
  13. 100% | [Strobe]
  14. Strobe | [100%]
  15. 100% | [Blink1]
  16. 5% - 33% - 100% - Blink1 - Blink 3 - Beacon | [Strobe]

moppydrv ​Instructions



  • short tap switches the light on to the previously used mode, or off if the light is already on.
  • press & hold while the light is on cycles through the modes in the selected mode group.  
    • press & hold while the light is off switches the light on in the first mode of the selected group.
  • double-click from either off or on puts the light into the special designated mode in that particular mode group.

To switch mode groups: rapidly tap the switch 8 times from either off or on.  The light will then enter the programming mode and begin to flash, reading out the battery charge state.  With the light in programming mode, tap the switch the same number of times as your desired mode group.  The light will blink and your mode group will be memorized. 


Example: To select mode group 3, tap the switch 8 times quickly to enter programming mode.  When the light enters programming mode and beings flashing, tap the switch three times.  The light will blink to recognize the mode group change.


To set the turbo timer: rapidly tap the switch 8 times.  The light will then enter the programming mode and begin to flash.  With the light in programming mode, tap the switch 20 times to enter the turbo timer set mode.  The light will then switch to 100% power.  When the light is at the desired temperature for the turbo step down, turn the light off.  The turbo timer will then be set.  The turbo timer steps the light down to 50% regardless of the mode group set.  To disable the turbo timer, simply set the time to under 4 seconds.  

Input Voltage / LVP Options:

  • 1S (~3V rampdown)
    • This is used for a single cell, or multiple cells in parallel (4.2v)
    • This is the most common SRK / soupcan light configuration
  • 2S (~6V rampdown)
    • For two cells in series (8.4v)
    • Includes LDO
  • 3S (~9V rampdown)
    • For three cells in series (12.6v)
    • Includes LDO
    • No 7135 Option
  • 4S (~12V rampdown)
    • For four cells in series (16.8v)
    • Includes LDO
    • No 7135 Option


This board was created with the collaboration of many of the great members over at BLF such as Mattaus and comfychair, along with JonnyC with help on the firmware.  Check out this thread for more information.

Write a review

Your Name:

Your Review: Note: HTML is not translated!

Rating: Bad           Good

Enter the code in the box below:

Powered By Lumens
Mountain Electronics LLC © 2023