week 03 | 2016/02/17 - 2016/02/24 | electronics production
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This week I had to produce a FabISP by myself. I've seen PCB production like etching, milling when Christoph did this in our FabLab/labor all the time. But this time, it is the first time to produce a PCB by myself. Instead of using one of the existing designs, I decided to go through the whole process to learn to design schematics and produce PCBs , while soldering SMD parts (even 0402) is nothing new for me. As I normally use OSX, I wanted to use a native and open-source program which gave me the option to try KiCad.
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The requirements for this assignment were simple: every FabLab should be able to produce them. This excludes all the wicked stuff and options like solder resist, stencil, ENIG etc. - but it does not exclude the option to make through-hole connections with our toggle lever press, which is very affordable (~$330) and could be replaced with enameled copper wire. I tried to design my whole PCB on a 1-sided PCB, but failed with routing one circuit path, which forced me to use the second side. To reduce the number of holes and save a lot of space, I tried to use as much SMD parts as I could. Under normal conditions, I would solder such PCB in our forced air circulation oven TR60 from Nabertherm. Instead of using this oven, my goal was to verify if this PCB is solderable by hand, because not every FabLab owns a reflow oven.
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My design is based on David's design with some modifications. I've added two LEDs, changed the Mini-USB-B connector to a USB-B connector and changed some packages. Here is my BOM...
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1 Attiny44A-SSU 68T3711 Newark
1 7A-12.000MAAJ-T CRYSTAL, 12MHZ 84R5400 Newark
2 Zener diode 3.3V 12T1447 Newark
1 3M ribbon cable 28AWG 98K8815 Newark
3 RC0603FR-071K5L 1.5kOhm resistor 68R0045 Newark
1 MCWR06X1002FTL 10kOhm resistor 94X1379 Newark
2 MC0063W0603148R7 48.7Ohm resistor 26M0947 Newark
1 GRM188R61A106ME69D 10 µF capacitor 31Y1762 Newark
1 TE 1734346 USB B connector 31M6448 Newark
1 0.1µF 0603 capacitor (in stock before)
2 18pF 0402 capacitor (in stock before)
2 LEDs 0603 (in stock before)
1 2x3 pin header w/ shroud (in stock before)
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Download my modded FabISP firmware
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After editing a lot of pictures, I decided to seperate the different stages of this assignment.
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Stage 1: Schematic, create parts/footprints, routing
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Stage 2: PCB production, milling
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Stage 3: Soldering, initial startup
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This work by Daniel Bruns is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.