Hardware

Block Level Design

FrothFET Block Level Design

Controllable Loads

FrothFET is designed to control just about any DC load, up to 20A. This includes, but is not limited to:

  • LED lighting (dimmable or on/off)
  • Pumps
  • Motors
  • Solenoids
  • Relays
  • Fans
  • Other Electronics
  • Buzzers / Speakers
  • DC Heaters

Where To Buy

Details on how to get FrothFET here

Revisions

  • Revision F — latest version
  • Revision E - prototype
  • Revision D - prototype
  • Revision C - prototype
  • Revision B - prototype
  • Revision A - prototype

FrothFET hardware is fully open source and licensed under the Open Hardware License (OHL) license.

All hardware design files (schematics, gerbers, and BOM) are available on GitHub.

Changelog

Rev F Release Notes

Power & Regulation

  • 5V Regulator: Switched to RT7272B for improved efficiency.
  • USB Power: USB 5V now powers the ADC, buzzer, etc.
  • Traces: Beefed up 5V traces and added a partial 3.3V power plane.
  • Level Shifting: Added 3.3V to 5.0V level shifter for RGB LEDs.

Control & Logic

  • ESP32-S3: Pulled in updated schematic.
  • PWM Buffers: Added buffer to PWM pins for better MOSFET control.
    • Accepted parts: 74VHC540FT, 74VHC541FT, 74LVC540A, or 74LVC541A (TSSOP-20).
    • Added Output Enable (OE) pin from ESP32-S3 to buffer (with pullup resistor to keep disabled during boot).
    • Added pullup resistors to buffer outputs to ensure MOSFETs remain off during boot.
  • OV Pin: Changed pulldown to pullup on the LM74502H OV pin (PWM).

Sensing & ADC

  • Current Sensing: Switched to INA226 with 2mΩ / 3920 shunt resistor (C5224159, ASR-F-5-2F, etc.).
    • Added support for the ALERT pin from INA226 for overcurrent protection.
  • Temp Sensor: Improved thermal coupling; sensor now has copper from the power trace running underneath.
  • Clean-up: Removed old ADC VREF, MCP3526R ADC schematic, and bleed circuit.

Protection & Safety

  • Fuses:
    • Changed to 3 separate fuse clips for the channel fuse (C41371870).
    • Moved bypass fuse to only bypass the MOSFET; the shunt resistor is now solid.
  • ESD: Added ESD protection to each channel output.

Connectors & Mechanical

  • Mounting: Switched to SMTSO3080CTJ for mounting holes.
  • Connectors:
    • Added Qwiic connector.
    • Added generic pin header.
    • Changed to XFCN 507 (replaced JLC unavailable part).
  • Test Points:
    • Added test points for 3.3V, 5.0V, 24V, GND, SDA, SCL, MOSFET Gate, Load+, etc.
    • Standardized all test points to 1.5 x 0.7mm.

Rev E

Upgrades based on real world usage of the Rev D. Changes include:

  • switched to on-board esp32-s3 instead of devkit module
  • changed to LM74502H gate driver to bring price down (about $2 vs $6)
  • added WS2812B leds to each channel for more informative channel status
  • fixed error with adc irq being unconnected
  • added piezo buzzer
  • changed to TPS7A2033 adc voltage regulator and REF3533 voltage reference chips
  • added a few extra ESD and overvoltage protections
  • changed to actual barrier screw terminals for positive connections
  • positive busbar now longer so cables can safely come out the bottom of board as well as sides
  • fan control now has an on/off mosfet in addition to pwm for using simple 2 or 3 wire fans
  • changed to TMCS1108 for current measurement due to supply issues

Rev D

Biggest change is moving to the LTC7004 gate driver chip to enable PWM control and a switch to N-channel mosfets.

Some other changes:

  • Switched to a 4 layer PCB
  • Added individual channel voltage monitoring
  • Added separate ADC VCC regulator

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