Homemade Hardware Week 3: Milling Custom Boards on the Othermill
My assigned letter for the custom PCB assignment was T. I started out by designing the schematic and board in Eagle, using the transistor board from week two as a guide. I chose to use a potentiometer as my input source, to dim and brighten the green LEDs on my board.
Next, it was time to mill the board on the Othermill. I followed the steps from the guide religiously and didn’t have too many problems (other than breaking my engraving bit…I’ve since bought another.)
Once the board was milled, I gathered the components and solderpaste and began to assemble the board. This is where I made my first of several errors: I accidentally used 220k ohm resistors instead of the 220 ohm. I also used an uneven amount of solder paste, which resulted in several of my resistors “tombstoning.” Surface mounting is definitely a challenge!
After everything was soldered (and re-soldered) on, I couldn’t get my LEDs to light up. I re-wrote my Arduino code to be consistent with the ATTiny85 pinout. I beep tested EVERYTHING with the multimeter, which is when I discovered how strong the resistors were. That led to me needing to desolder eleven resistors and replace them with the correct strength of resistor (well, close to that, because I couldn’t find the 220k resistors in the hard lab.) Still, my LEDs wouldn’t light up. Finally, after an hour of fruitless de-bugging, James figured out that my potentiometer wasn’t pushed in enough to my header pins. And voila! It worked.