Our instructor this week was Antti Mäntyniemi. This week we need to design a micro with an outpout. We have to make something do something. I have decided to go with Charlieplexing. I have a lot of LEDS in my final project, and up to now, I am going on using ATtiny44A. So I think it will be good to learn how to handle multiple LEDs with small amount of pins. Also, I know there is neopixel, and I might use it at some point. But I feel chalieplexing will allow me more flexibility on where to put the LEDs. I want to try to do a tower of LEDs. Basically, I am experimenting a bit on LEDs
- Understand charlieplexing
- Understand how to build the tower of LEDS
- Design the boards and mill them and solder them
- Group work
Charlieplexing and The Tower
- 3 possible states of the pins: High, low and High resistance
- Persistence of vision
- The LED working curve, with the different areas: no glowing, dim, operating, burnout
Checking other's work for creating cubes, I managed to understand how to create a clear schematic for identifying the different LEDS and lines.
Then, I have decided to use 4 pins of the ATtiny44A as starters. This means I can use up to 4*3 = 12 LEDs. So I create the schematic, 2D view structure and "3D" view structure for 12 LEDs.
Building the towerFirst, to solder the LEDs together, I need a support for them. The fastest way was to use some blue-tack like material to create a "mould". Then, I solder each layer, for a total of four. Then I can start to solder the layers together. I have to go layer by layer, checking the connections from the design above. I would need to plan a bit better the connections next time.
Design, milling, soldering
I wanted to link this to the input board, but I decided to also make a board with a button, to interact with the output, and later link the two boards.
Microcontroller board For soldering the resistors board, the bill of Materials:
- 5 110ohms resistors
- 2 3x2 header pins
I started with a breadboard, as I did not have the tower of LEDs built yet. I wanted to test the structure of LEDs first, and then build the tower. I am not adding a picture of that, because it was really a mess of cables a pin heads.
Once it worked well in the breadboard, I moved to the tower of LEDs.
- I have understood how Charlieplexing works
- I have learnt to create an schematic for charlieplexing
- I have learnt how, with the correct schematic, it is possible to build a tower of LEDs for Charlieplexing
- Time, time, time... (again)
- understand how to build the tower
- Take it easy with the milling: things happen.
- Keep on checking shorts on freshly milled boards, even when you do not have much time. This can save a lot of time afterwards.
- I usually check for shorts in the board before soldering. This time I was in a hurry, and did not do it very well. This a paid afterwards, as I had some shorts beneath a soldered pin head
- To solder the LEDs, it is really necessary to have a mould
- main.c C file for showing patters of lights in charlieplexing when pressing a button
- Eagle board file and Eagle schematic file for the board: microcontroller
- Outline for the controller board
- Traces for the controller board
- Eagle board file and Eagle schematic file for the board: button
- Outline for the button board
- Traces for the button board
- Eagle board file and Eagle schematic file for the board: resistors
- Outline for the resistors board
- Traces for the resistors board