Electronics Design
For this week’s assignment we had to redraw an echo hello-world board, and add (at least) a button and LED (with current-limiting resistors).
Group work
Schematic Design
I selected the IC (Attiny 44) and the board version that I wanted to redraw, I decided to add a switch and RBG LED to my board. I opened a new EAGLE schematic to redraw the circuit, but before starting, I had to download the fab library to EAGLE libraries to be available to use, so I downloaded it to my PC and opened from the schematic window, Libraries then selected libraries manager and then browsed the fab library and selected it.
Then I started selecting the components to my schematic, by just clicking the add part button and selecting the component name from the drop down menu, since the names of the components in the library may be different from the names we know, I had some troubles recognizing them , but our electronics engineer in the lab Yazan, and my instructor Nadine helped me with this problem, so I listed down all the components names in the fab library.
| # Used | Component Name | the Fab Library Name |
|---|---|---|
| 1 | switch | 6mm_switch_6mm |
| 1 | Attiny 44 IC | attiny44-SSU |
| 6 | Reasistors | RES-US1206FAB (RES-US) |
| 1 | Capacitors | CAP-US1206FAB (CAP-US) |
| 1 | ISP | AVRISPSMD (AVRISP) |
| 1 | FTDI Pin Header | FTDI-SMDH-EADER |
| 1 | Crystal | RESONATOR |
| 1 | Jack | JACK.65MM (JACK) |
| 1 | RGB Led | LEDRGBNEW |
The next step was to connect all components together, I could use the line connections, but I selected the naming option to keep the schematic clear and easy to edit. I started connecting the coponents by giving each mutual end the same name.
for the switch I connected one end with the IC and the other with the ground, and from the IC connection I added in parallel a large resistor and then a VCC.
For the RBG LED I read in its manual that the blue and green ones needs more power to light, so I decided to give them a smaller resistors than the red led, from the sheet the forward current for the red led was 25AMP and the voltage V, so by simple calculations the resistor equals 90 ohm, but since we don’t have 90 ohm resistor I used a 100 ohm resistor, and for the green and blue I used a half value resistors.
The Board Design
After finishing the schematic I opened the board from the top left button in eagle, in the board all the components show out of the area, so I started dragging them in to draw the traces. Before start drawing the traces I had to change the clearance values and the diameter size for the trace, to match the 1/64 inch diameter tool that I will use in Rolland.
After that, I started arranging the components in the area, I tried to stack them in the best way I could, then I started to draw the traces between them. After finishing all the connections I had one line left and couldent connect it without changing almost every thing, so I had to add a zero-ohm resistor to act like a jumper.
Then I had to export the traces and the outlines as a png images to mill them using our milling Rolland, so I select hide for all the layers except the Top and pads .in the option drop down menu go to setthen misc and unselected the display for all names and icons. then exported the file as a monochrome and with 1500 px resolution, and did the same with the outline but by showing the dimensions layer only. But for the outline image, I went to 3D paint and edited its inside contours to be white, and the outline borders kept black, so the FAB MOD can recognize the races better.
Production
By achieving this point, I had finished all this week’s new topics, and started producing the board exactly as we learned in the production week, I used the fab modules interface, selected the exported image from the EAGLE as an input, and selected the output to be Rolland milling, and the process for the traces to be trace 1/64, and for the outlines to be outline 1/32. All the settings I selected for each image is shown in the pictures below.
For the Rolland, I set the XY-zero first, and started setting the Z-axis to its zero to be touching the board, I used the digital multimeter to check the connectivity between the mill and the copper sheet, then I set the point as a z-zero. After that I pulled it up from the surface, and gave the machine the cut order.
After the board traces and outlines finished, I pulled it off, and cleaned it using a tooth brush dedicated to clean the PCBs in the lab, and then I covered all the traces with the flux and the copper to make the soldering process easier.
The I collected all my components and started soldering them to the board, it’s the fun part for me though its hard task. see below the final result.
Testing the boared
the last step in this assignment is to test my board, using arduino. I will list down the testing steps, and I will atach photos of the whole process once we back to the lab.
- connect your arduino to the pc and open the arduino software.
- from files >> examples >> arduinoISP.
- from the tools menu slelect the arduino type and the port as shown below.
- click upload, it will start compiling and will give you DONE massage.
- connect your board to the aruuino, and open a new empty file from arduino software.
- if this is your first time to programm an attiny in your pc, you might need to download IC library so you can find attiny44 in your boards list in the arduino. to do so follow the steps in this tutorial.
- from the tools menu set the settings for the board as shown below.
- select burn bootloader.
- after it finish, open any example from the files menu, I opend blink example.
- edit in the codethe pins numbers depending in your board pins.
- from sketch menu, click on Upload using programmer, and your board should start blinking.
Board Design