PCBs
Milling
Milling the board was rather straightforward, since I had the luck to watch and learn from the mistakes of the students before me. First, one problem that I saw was that the milling bit was broken, so some of the traces weren't milled. In addition, I didn't securely tape down the first board that I tried to mill, so once I started milling deeper for the outline, the board detached from the platform and I had to remill another board.
Soldering
- Get a tile, a spray bottle, and a soldering iron
- Wet the sponge of the soldering iron
- Iron should be around 680 F
- Use tweezers to manipulate surface-mount components
- Place your hand over clippers when you cut components so they don't go flying
There's a very helpful tutorial for learning how the FabISP works. ISP stands for in-system programming, which means that the microcontroller can be programmed while installed in a system. The RST line is used to reset the ISP (by setting RST to high), which also enables MOSI, MISO, SCK.
Components
- FCI header: 6 pins
- atTiny44A-SSU
- mini USB 2.0
- Zener diode
- Kirchoff's voltage and current laws
- Remove high-frequency variations in voltage, always add at least one of these to an integrated circuit (0.1 microFarad usually works)
- Decoupling capacitor
- Remove high-frequency variations in voltage, always add at least one of these to an integrated circuit (0.1 microFarad usually works)
- Diodes
- Allow current to move in one direction but not the other, usually made up of semiconducting materials.
- Differential signals
- One signal goes down one trace, and the opposite signal travels down a parallel trace. If the two signals are subtracted, noise canceling is achieved. The traces must be equal in length, so that the signals travel the same distance and are in sync. They should be close together, so that induction effects aren't significant and so that noise in one trace is closely mirrored in the other trace. Traces must be a constant width apart, since trace impedence/coupling must remain constant over the entire trace length.
- Microcontroller
- A small computer containing memory, a processor, and input/output
- Pullup resistor
- A resistor connecting an input to a power supply, along with a connection to ground: https://learn.sparkfun.com/tutorials/pull-up-resistors. There is usually a switch/button involved. When the switch is closed, the input is at voltage level 0. When the switch is open, the input is at voltage level V.
- Voltage clippers
- Usually made by adding a diode to an AC circuit. When the diode is forward biased, the waveform is clipped because there is little voltage drop across the diode.
