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This is a small board to drive eight opto-isolators from an i2c GPIO expander,  to be connected to the i2c bus of an embedded board.

I designed this board to interact remotely with the various devices in my board farm.  It is used to control system reset, system wake-up, and soft power-on for the individual boards, and to power on/off the board farm main power supply (power to the individual boards is controlled differently).

Of course it can be used to mimic keypresses or deliver "open collector" (or emitter) signals in other projects.

Please see my presentation "Herd Your Boards, Become a Farmer" at the Embedded Linux Conference Europe 2016 for more information:

Noteworthy slides:

  • Slide 25 contains the rationale behind using optocouplers,
  • Slide 26 shows v1 of the board (on protoboard),
  • Slide 40-42 show the "software setup".

KiCad board design files: https://github.com/geertu/Optoboard (CC-BY-SA-4.0)

Parts

Name Description
9x D3 / D1 / D2 / D4 / D5 / D6 / D7 / D8 / D9 LED YELLOW CLEAR 0805 SMD
2x R2 / R1 Res Thick Film 0805 4.7K Ohm 1% 1/8W ±100ppm/°C Molded SMD SMD Paper Tape on Plastic Reel
8x R15 / R13 / R18 / R11 / R12 / R14 / R16 / R17 Res Thick Film 0805 220 Ohm 1% 1/8W ±100ppm/°C Molded SMD SMD Paper Tape on Plastic Reel
2x P2 / P1 PH Series 4 Position 2 mm Pitch Through Hole Crimp Top Entry Shrouded Header
9x R10 / R19 / R3 / R4 / R5 / R6 / R7 / R8 / R9 Res Thick Film 0805 1K Ohm 1% 1/8W ±100ppm/°C Molded SMD SMD Paper Tape on Plastic Reel
8x U9 / U8 / U7 / U6 / U5 / U4 / U3 / U2 Optocoupler DC-IN 1-CH Transistor DC-OUT 4-Pin Mini-Flat T/R
1x U1 Remote 8-Bit I/O Expander for I2C-Bus 16-SOIC -40 to 85
1x C1 CAP CER 0.1UF 50V X7R 0805

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