fischertechnik I2C port expander

thingiverse

Changelog:\r\n2019-03-27: Files for etching PCB in extended gerber, PDF, and SVG formats added to archive PCB.zip (cf. last two images)\r\n\r\nThis easy-to-build PCB with printed enclosure offers an additional 8 digital inputs or 25mA outputs and 8 outputs with 500mA each, controlled by I2C. It's based on the MCP23017 16-Bit I2C I/O Expander, with outputs driven by a ULN2803.\r\n\r\nThe enclosure has connectors for fischertechnik construction toy system and uses printed flush sleeve design ("Printbuchse") for fischertechnik typical 2.6mm jacks. Outputs can drive ft-parts like lamps, magnets, valves, or (undirectional, mono-speed) motors. Combine two or more ULN2803 driven outputs if you need more than 500mA.\r\n\r\n* The 2x3 pin I2C connector is pin compatible with other ft I2C cables (ftDuino, TX).\r\n* MCP23017's specs show the expander should work both with 5V or 3.3V I2C devices; only tested 5V, though.\r\n* The I2C address can be changed by DIP switches hidden under a print-in-place cover.\r\n* The fourth DIP switch connects interrupt B of MCP23017 to one of the unused I2C connector pins.\r\n* Two male headers provide access to interrupts A and B.\r\n* For Arduino, use this Adafruit library: Outputs are 0 to 7, Inputs are 8 to 15; don't forget to activate internal pull-ups.\r\n\r\nI'm not an electronics expert, so use my circuit at your own risk. And yes, Fritzing sucks at turning out proper schematics, but it's what I know.\r\n\r\nPlease consider leaving a "like" or posting your make as a token of appreciation for my work.\r\n\r\nFind my other fischertechnik designs here: https://www.thingiverse.com/juh/designs.\r\n\r\nhttps://youtu.be/QT0vX92g17Y