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PWM Lighting Adapter

4x N-Channel MOSFETs designed to fit on common PCA9685 modules

Overview

An extremely simple test of using a commonly available PCA9685 module to modulate low-power LEDs like DC puck lights. Each module has 4 N-channel MOSFETs rated at a max power dissipation of 7w and were chosen without much knowledge of how to choose MOSFETs.
A handful of these have been in service for over a year without issue, but only seem to be useful for puck lights and short LED strips. Much more capable MOSFETs are available in a similar package size.
This is likely a stepping stone to better design. It answered a lot of questions while in use.

Problems

The intent of these boards were to improve ease of deployment, but there are several issues with this design.
  • Output is intended for 2.54mm 1x2P pin headers requires crimping dupont connectors if they aren't already installed or wiring needs to be extended.
    • Lesson: Don't design to what's on hand - re-ordering the same thing presented a different connector.
  • Soldering the board was a pain
    • The last pin header was oriented at a right angle to the rest requiring a separate 2p header
    • Was originally designed for individual sets of 2p headers for some reason
    • The 4P female headers were also hard to solder due to diving board effects.
    • Screw terminals suck in general - always use spring connectors moving forward.
  • Mounting wasn't taken into account
    • A DIN Rail adapter was designed for the PCA9685 board, but it was only implemented in one deployment.
  • Cable management wasn't taken into account
    • Eventually using right angle pin headers helped with this, but still a PITA
  • Silkscreen wasn't clear about polarity
    • Constantly checking other boards or docs when changes are made

Design Files

This project was made in EasyEDA and will be available via OSHWLab
TODO: Links