This week is about designing a PCB board with a micro-controller and understand it by displaying the in and output. First find out how our lab equipment works. Than individually redesign a ‘Hello World’ board, Mill it, Solder it and program it. We will use A LED an LDR and button as input and output.

  extra credit: simulate its operation

How can I use this in my final project?

  • I need to know how logic works
  • I need a PCB for WiFi (ESP)
  • I need a PCB to heat the wires (30 mosfets)
  • I need to use serial communication to drive these mosfets with one dataline
  • I need

The steps for this assignment

1. Group: use the test equipment in your lab

Use the test equipment in our lab to observe the operation of a microcontroller circuit board read all about this group assignment

2. Draw the schematics to redesign the ‘Hello World board’

We had instruction using KiCad, but since I didn’t like the UI so mutch I tried Fusion Eagle. To get started is really hard, just like Fusion 360. I watched this video to get the basics.


0Ad the fab Library to eagleI downloaded the Fab library and followed this nice manual ‘how to install an Library (including footprints) in Eagle’
1Here are the components
2When ready with placement press escape
3Drawing wires works simular
4While drawing, rightclick is rotate. Escape= end of wire
5To connect wires you use Labels
6You Add the labels to the wires, not the components
7First select the name change
8Then click the wire to rename the wire
10If the name you enter is similar to a name on one of the other wires. The wires will be ‘connected’
11First select a component, than in the information panel, enter the value
12Final check of the scemetitics. Printed

Mistakes/mental notes

  1. It took me a few hours to find out eagle was not working with shortcuts. You first activate the command line mode (use CMD-L). Then type the command. Most used commands are
    • Net: for a wire
    • Label: label wires to ‘connect invisible
    • Move: move a part or wire
  2. I didn’t understand the connection between a label and a name… So I first added labels and than changed the names in the labels. To find out a ‘name’ is the text in a ‘label’…
  3. The workflow for Eagle is: select a action, then apply this action to all components/wires. The steps I took are more from the mental model of the object. Next time I will first put ALL down > name/value ALL > wire ALL > move ALL etc.

The result

3. Design the PCB

1First try placing the components. I started with the component with the most legs, placed it in the center
2The name labels are really disturbing, so I wanted to remove them
3You can alter the view settings by First selecting the component with Group and disable the Value or name
4It took me some time to find out why I was so frustrated selecting components (with the Group tool). You have to Click the Cross to select a component
5My fist atempt of many, just ONE Airwire to go
6I found out switching off the labels (name and or value is a lot better in the layers)
7I got rid of the labels, but still no luck in generating a PCB
8Looked for strategies to place components. But besides first placing the components with most connections and than starting to draw VCC and GND, I found not MuchAutodesk PCB placement tips for beginners

Problem - traces too narrow

I managed to create a board. But the traces are too narrow

So I had to remove all the wires and I desided to set the Design rules for the board (Henk explained this for Kicad but not for Eagle).

3.1 Set the Design Rules for the board

1Tools > DRC
2Feedback error: One ‘Airwire’
3The GND wire was not connected
4I re-draw the wire with ‘Redraw Airwire’ and this error was solved. Then only 25 Errors remained…
5I used the page of Catherine Blanchard
6After redrawing I went to Tools > DRC… > Check. A new error appeared. A small piece of copper was behind the VCC. I removed it.
7Again did the DRC check. No more Errors. But this is very subtle in the UI.
8Before export as PNG, make the label visible you would like to export
9Match the resolution of the exported image to the resolution of the milling machine

I used these settings for DRC

Lessons learned

  • When not setting the design rules, wiretraces and distance between traces will not work for our specific milling machine. First set the Design rules, than draw the board!

mental note

  • In eagle use the command line (most used move, name, value, trace, delete, ripup DRC)

The result

4. Mill the board

For the milling of the boards I used the steps of week 4

1While milling the mill went to the outside of the board. It turned out the board was to big.
2Measuring the board in Eagle and in real life it turned out my board was twice the size
3The Same image in Eagle 35,6 x 45.21 mm and in Mods 71.20 x 81,43 mm!!! So exactly twice the size. Both settings are 1000 dpi
4This post in autodesk mentions the same problem 
5I changed the setting in the Image MOD to 2000 DPI. Now the dimensions are right.
6milling the traces went well, But milling the outline didn’t work well. I forgot to lower mill enough. The head was in its lowest position. So I put the Mill down and started the outline again.
7The outcome was disappointing Two pads where connected.
8I should have been looking in the MODS: VIEW. Before milling
9I moved the traces a bit and now the mill will divide the copper.
10But I had a board and not so much time… So for the first version I Used a knife to cut away the false copper I used the Multimeter to make sure I succeeded to insulate the traces.

Thanks to my global evaluator I found out one of the connections I had to cut was coused by text over the pad. Next time I will use these settings to make names and values smaller: Thank you Yuichitamiya!

5. Program the board

1I looked at the scematics of my AttinyISP and the Hello44Harmboard to see how I should connect these board via a Flatcable.
2This should be the way to connect both boards
3[I looked at the steps Joey van der Bie took last year
4Connected the board to my USB 2.0 hub and tested. But It could Not talk to the ATTiny44 Hello board ;-(
5I looked up how the MiSo Mosi etc pins of the 44 should be connected in the 44 Datasheet
7And put the pin number next to the PSI header. I used the continuity setting on the multimeter to see if the pins on the PSI header on the SPI where connected to the ATtiny44 chip
7I looked for the connections, But the RST was not connected to the board.
8IN the schemetics the Reset was simply not available
9I Added the label for the next version of the board
10But first tried if I could fix the board with a Wire
11Tried again “avrdude: Error: Could not find USBtiny device (0x1781/0xc9f)
12I tried ioreg -p IOUSB to see if my laptop could ‘see’ the TinyISP. Even this didn’t work anymore 
11DON’T connect without the USB2. 0 adaptor!!
12This is the right way
11Now it works!

5.1 Test the board (Using Arduino)

I wanted to test the board and the sensors and actuators. So I tried to program the board with Arduino IDE. But Didn’t know how to address the LED, Button. Thanks to Hyjin’s page I managed to find the library where the setting are. But only for the 84. With some help from Henk we found the 84 is a bit better. More memory etc. But pin-outs are the same on the WIKI page of the ATtiny

In the header file ‘pins.h’ file in /Users/harmvanvugt/Library/Arduino15/packages/attiny/hardware/avr/1.0.2/variants/tiny14 I found:

//                           +-\/-+
//                     VCC  1|    |14  GND
//             (D 10)  PB0  2|    |13  AREF (D  0)
//             (D  9)  PB1  3|    |12  PA1  (D  1) 
//                     PB3  4|    |11  PA2  (D  2) 
//  PWM  INT0  (D  8)  PB2  5|    |10  PA3  (D  3) 
//  PWM        (D  7)  PA7  6|    |9   PA4  (D  4) 
//  PWM        (D  6)  PA6  7|    |8   PA5  (D  5)        PWM
//                           +----+

I looked in my schematics of the board and this should be the way to address the components:

Componentconnection on chipCode (pin)

To test the button, the LED and the Photo Transistor I made a code where:

  • Default the LED is on
  • But if you press the button, the led blinks. With the frequency of the light on the Photo transistor.

In code it looks like this:

int ledPin = 7;
int buttonPin = 3;
int knoppie = 0;
int sensorPin = 2;

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP);

void loop() {
  knoppie = digitalRead(buttonPin);
  int sensorWaarde = analogRead (sensorPin);

  if (knoppie) {
    digitalWrite(ledPin, HIGH);
  }  else {
    digitalWrite(ledPin, HIGH);
    delay (sensorWaarde / 50); //I divided the sensor-value by 50, it was trail and error. 
    digitalWrite(ledPin, LOW);
    delay (sensorWaarde / 50);

At first this code Didn’t work. The led was simply ON. I remembered I had a lot of doubt when soldering the Photo transistor. I could choose one out of 3 and couldn’t rationale which was the correct one. With some help form Tessel she found the data-sheet and since the package should be 1206, I picked the one with 1206 package.

Hero Shots

Not working? Youtube to the rescue


Final conclusion for this week

Conclusion on the process of electronics design

  • Don’t rush: The process of electronics production is a slow one. Every tiny mistake will have huge consequenses at the end.
  • Work in series: don’t jump from one step to the other in the process. First complete AND check the step and than continue with the next one
  • For a next electronics design I have to really rethink how I set up Eagle. Now the grid and the traces do not perfectly align with the components.
  • Electronics production is Hard, how can Electrics be so cheap???

Biggest Mistakes and lessons this week Other from the ons described in all the steps in this page ;-)

  • In Eagle: Set the Design rules before designing the PCB
  • In the Mods for milling: Check the traces before starting the Miller

Wat went really good

  • When I finally understood the idea behind Eagle is was okey to work with.
  • I liked the soldering
  • I liked the end result, the LED blinks depending on the quantity of light

My concerns

  • If I have to produce a complex board, with Internet connection in my final project, I need mere than two weeks to complete this. So fall-back would be an ‘almost ready’ WiFi micro-controller and custom made boards for input and output…

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