I like making small and good looking boards. When doing Charlieplexing, two LEDs share one pin, meaning the resistor should be divided in half to supply with the right amount of current. That gave me a required resistance of 100 ohm. I bought LEDs with a forward voltage of 2V, and I wanted to keep the current through the LED at 10 mA. It is important to me that the LEDs shine bright, but I also didn't want to burn out the pins that can do a maximum of 20mA. I calculated the value for the resistors connected to the LEDs using Ohm Law Resistance equals the voltage source minus the voltage drop from the LED divided by the current running through the LED R=(V SOUCE-V LED)/I LED.
How to connect the cable when programming the board and reading serial Orientation and placement of LEDs Pin out Orientation of sensors I make notes to remember the orientation of the board, the anode and cathode of the LEDs, the different pins and which wire should go where.
PGN file ready for tracing PGN file ready for cutting Settings in Mods Mods show the traces Newly cut board Prior to soldering I made sure I had all components
The holes are part of the cut file, and you have to make sure the holes are bigger than the diameter of your tool. I cut the board using the Roland MDX-20 milling machine, first the traces and then the cutting, just like in previous weeks but this time I also made holes.
I decided that I wanted to place the battery on the back of the board, but not using a two-sided copper board, but to make through-hole design instead. I had to use three 0 Ohm resistors to jump a few traces. The hardest part is always to have enough space for the traces going from the ATtiny and out to the different components. The board design is always a bit more tricky and time-consuming. Making the schematic in Eagle wasn’t that hard after all these weeks of making boards. Since my cube is made to be taken apart, the battery can be changed when it runs out. The voltage is also enough to run my board.
I wanted a coin battery since that doesn’t take up that much space. The cube runs on a 3V coin battery placed on the backside of the board. I read this one and this one about Charlieplexing to understand what was needed for that. I followed this tutorial about capacitive sensors to get a better understanding of the components and the connections. I designed my board and decided the components based on similar boards I have been doing during the Fab Academy, the Echo Hello board gave me a good understanding of the main components the ATtiny84, the resonator that I would use as my external clock, the 10k Ohm resistor connected from the reset pin to VCC, the connections on the 6-pin header to be able to program the board, the capacitor between VCC and GND, etc. My final project in greater detail The different parts of the interactive cardboard cube