What's new:
- Firmware open source - The board is Arduino- compatible (behaves like a Sparkfun Pro micro 5v/16MHz) so that you can program it with a USB cable and Arduino IDE.
- More precise - The new linescan image sensor is a bit more precise (90% pixel size of V3). Also the D to A conversion is improved, and the output has a 2nd order filter and buffer amp to improve the signal.
- I2C output - The board outputs the micrometer reading via I2C digital output compatible with 3v or 5v MCUs.
- USB Serial output - The board has USB serial output of the micrometer reading, so could be connected to a PC or Raspberry Pi (Want to write an Octoprint plugin?).
- It Exists! - With the demise of the TSL1401CL image sensor, and inexpensive linescan image sensors in general. Its been hard to find a suitable replacement. This design uses the Melexis MLX75306, which is 2X as expensive and is unfortunately harder to get.
What's the same as the prior version:
- Power supply: The filament sensor is powered by 5v.
- Analog output: The sensor outputs a voltage in milimeters ( ie 1.50v=1.50mm, 2.00v=2.00mm,...) that can be read by a voltmeter, Arduino analog pin, or anything that accepts a 0-5v voltage input.
- Principle of operation: Still the same, subpixel image processing of the shadow of the filament to detect the edges.
What's lost:
- Image Sensor TSL1401CL: Prototypes 1-3 relied on this great image sensor, which was inexpensive, worked well, and ran at 5v. The sensor is no longer manufactured, so I had to find a replacement.
- Simplicity - The circuit is more complex to support the new interfaces, Arduino compatibility, and the line-scan image sensor.
- Form Factor - The board is very similar in size, but it will not fit in the housings of V3 as components have been moved on the board and get in the way.