46mm SRK FET V2 PCB - Bare DIY

46mm SRK FET V2 PCB - Bare DIY
Product Code: SRKFETV2-PCB
Availability: 50
Price: $4.25

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This is an updated version of the popular SRK FET driver PCB.  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.  

Once built, 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.  

The PCB 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. 

Parts kit. 


  • 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 
  • 7135 for extra-low and efficient moonlight mode (1S and 2S only)

Parts List:

REQUIRED Parts List (1S Input):

  • FET: D2PAK
  • RGATE: 0805 - 10 ohm - 100 ohm
  • R1: 19.1K (1S input)
  • R2: 4.7K
  • U1: attiny13a-SSU
  • C1: 0805 - 10uF - X5R (or better)
  • D1: SOD-323 Schottky Diode

REQUIRED Parts List (2S+ Input):

  • FET: D2PAK
  • RGATE: 0805 - 10 ohm - 50 ohm
  • R1: 36K (2S-3S input)
  • R2: 4.7K
  • U1: attiny13a-SSU
  • C1: 0805 - 10uF - X5R (or better)
  • CLDO: 0805 - 10uF - X5R (or better)
  • LDO: Many fit - choose on price and availability - 5V variant preferred
    • A few that do fit:
    • LD2981 (can do up to 3S)
    • MIC5235 (can do up to 4S)


  • 7135: Optional 7135 for secondary PWM output (Pin 5)
  • OTC (for clicky FW use): 0805 - 1uF - X7R
  • Ctemp: 0805 Capacitor - 1uF - X7R
  • RT1; RT2; T-; T+: Connection points and related component pads for external temperature sensor


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.

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