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# Embedded Etcher
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Design files related to a photo-sensitive layering method etching machine
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everyone can build to produce prototypes quickly at home or in the lab.
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## Architecture
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The etching machine consists basically out of two parts. The
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first part is a UV light, which is used to develop a photo-sensitive PCB. Once
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this has been done. The PCB has to be treated with sodium hydroxide (NaOH)
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dissolved in water. This removes the UV-sensitive plastic, where it has been
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tackeled by the light.
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The second part is the actual etching machine, which is designed to be
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compatible to euro cards (and even bigger ones). The etching machine is either
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filled with sodium persulfate (Na<sub>2</sub>S<sub>2</sub>O<sub>8</sub>) or
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iron(III) chloride (FeCl<sub>3</sub>) dissolved in water of course.
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## Cuvette
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![alt text](https://github.com/m3x1m0m/ecthing/blob/master/photos/cuvette.jpg)
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## UV Light
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### Driver Extension Board
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![3D Preview from KiCad (1).](https://github.com/m3x1m0m/ecthing/blob/master/pcbs/extension_board/output/3d_pic_1.jpg)
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This PCB is made to fit the [Nucleo-F103RB](http://www.st.com/en/evaluation-tools/nucleo-f103rb.html)
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development board from STM. Features:
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- 64 LED driving stages
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- 6.4 A and 24 V max. input (0.1 A per stage)
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- 0.2 A max. and 350 mW dissipation max. per stage
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- 10 Bit DAC to steer the driver
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- Optional potentiometer to steer the drivers
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- Control-loop for constant current
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- Feedback amplification to get a high current resolution
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- I2C header
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- SPI header
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- 2 rotary encoders and 1 tactile switch
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![3D Preview from KiCad (2).](https://github.com/m3x1m0m/ecthing/blob/master/pcbs/extension_board/output/3d_pic_2.jpg)
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It is important to mention, that the resistors for the non-inverting amplifier
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in the feedback loop are optimized to result in a maximum current of 33 mA for
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3.3 V in order to achieve higher currents different resistor values have to be
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chosen.
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![alt text](https://github.com/m3x1m0m/ecthing/blob/master/photos/uv_lamp.jpg)
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## Etching Instruction
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TBD
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