Logic Level Low Side Switch

This is a hobby project and comes with no official support. The PCB schematic and board design files are offered 'as is' with no claims made about their fitness for any specific purpose.

A low-side, logic level MOSFET switch for use with ESP 8266, ESP32 and other 3.3V logic.

The PCB was designed for a Meshtastic node build that used a Heltec V3 (ESP32-based) board, but it can be used in many other situations.

In the original use case, the switch controls the power supply to a GPS module, allowing the Heltec V3 board to turn it on/off to save power. As well as the switched output, there's a pair of power rails that run from side to side on the board; these are provided as extra + and - connection points if needed.

The switch design is based on the Meshtastic recommendation below, with additional resistors to ensure proper MOSFET turn-off and to protect the I/O pin from ringing and current surges.

https://meshtastic.org/docs/hardware/devices/heltec-automation/lora32/peripherals/

The MOSFET can be any logic-level, N-Channel, low RDS type. The original design uses an AO3400A. If you use a different part, make sure it has the same pinout.

The board is laid out to support optional PCB pin headers, but these can be omitted to make the whole unit smaller. One build idea is to fit the the board with flying wires (with a bit of optional hot melt glue for strain relief) and then put the whole lot in some heatshrink tubing.

V1.0 of the board used 0603 size resistors, V1.1 uses 0805 to make DIY assembly a little easier.