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6. Electronic Design

Hero Shot of the Week

Editor

Summary

Half of this was new for me.
I already had some knowledge about electronic components, but still learned (or sometimes relearned) things.

The part that I most like is the design schematics. Putting down the little drawings, connecting them together, adding color coded lines... That was fun.
On the other hand making all that a realty, and making tracks is the PCB design was a real headache...
So many components that want to cross links...

Work Process

Calendar

Date To be done What was done
Thursday - Introduction by Henk and Erwin
- Introduction to a PCB printer
-		 - Done
- Postponed
-
Friday - FabLab normal work
Saturday - nothing, need time to recharge - thinking on what to design
Sunday - work on the design
Monday - Work on designing
- getting a headache with routing all the things together
Tuesday - FabLab normal work - repairing a 3D Printer
Wednesday - 12h Local
- 13h Regional
- 15h Global

Introduction

We got an introduction by Henk and Erwin.

Electronics & Electricity Basics

We got back to water analogy as with the discussion I had with a guy in the Zoom channel.

Also, a thing that also bugged me in the introduction is the how we constantly "simplify" kWh. The unit W has already time in it:

W = kg . m^2 . s^-3

With my (bio)engineering background I do have some electricity & electronic knowledge but I need to dig it up in my memory.

Components

Measuring and QC tools

  • multimeter
    • V measurement in parallel
    • A measurement in series
    • Black == Ground
    • Red == what we measure
    • it calculates an average signal
    • for DC signals
    • Analog signals

Manual MN35 Extech

  • Oscilloscope
    • measurement in time
    • for oscillating/AC signal
    • multiple signal measurement
    • analog signals
    • PWM measurement

Manual SDS 1072 CML+

  • Logic analyzer
    • digital signal
    • PWM measurement
    • Computer Data analysis
    • can translate the signal

Design

FabAc Library List
To add them to your Design program just follow the install instruction given on the Git page.

Component Search

KiCAD

Home Page

Collection of utilities.

Just like in Blender, you better know all your shortcuts.

And don't forget to add the Git libraries.

Schematic Editor
ShortCut What it does
a Opens Symbol Menu
e Add Annotations

Schematic menu

PCB Editor
ShortCut What it does
x Create Route Track (electronic connections on PCB)
F8 Update PCB drawing from Schematics

PCB menu

Use the Line Tool form the Edge.Cut Layer to define the size of the PCB.

Use SilkScreen Layer to add your text to the PCB.

PCB Side menu

Exporting for Fabrication & Fabrication Setup (not for this week but here it is):

Step 1:

  1. File > Plot
  2. Choose your parameters
  3. Verify Generate Drill Files settings (including the output format)
  4. Plot/Export the file

Step 2:

  1. Go to https://modsproject.org/
  2. right click to open menu
  3. open program
  4. select your machine
  5. import your SVG where it needs to be imported

Designer Check

File > Board Setup > Design Rules

The settings here depends on the Mill Head & the Machine.

Than you can run the integrated Design Rule Checker

Design Rules Help

Our design DRC:

DRC

Eagle

Home Page

Simulator

Spice

This weeks work

KiCAD

So we got some specific instruction from Henk on what our PCB design needs to include.

build around xiao rp2040 or esp32-s3
button
led (external, so the button on the xiao don't count)
and then either a
SPEAKER 8OHM 250MW
SENSOR PHOTO 940NM TOP VIEW 1206
and all the necessary resistors and capacitors
You are free to add your own in or output device

My first "trouble" was when I put the ESP32-S3 into the schematic editor and the number of physical pins (7x2) did not matchup with the pin number in KiCAD. Took some time to figure it out that there are pads underneath the ESP.

At the beginning I wanted to do something useful for my final project. But I could not think of anything.

Somehow the best idea that came up is to design something that could be used to send and receive morse code.

  • RGB Led for signals
  • 3 buttons
    • 1 for .
    • 1 for -
    • 1 for reset or other function
  • buzzer (or other speaker)
  • screen (if I still have enough pins)

initial idea

The issue now is that I am home and do not remember what we have at the FabLab...
Lets hope that what we use in design is what we have in stock.

ESP32

My second challenge was to find a socket for the ESP32. Somehow I have found that we have a generic socket for that in the FabAc repo. Thx Kris !

ESP32

Sound

For the buzzer, we were told to use the PSR-23F08S-JQ. Looking to the datasheet I did not found any specific connectivity.

Back to the FabLab, I cant find it. I will need to ask Axel if we have them in stock.

LED

For the LED I first took a random RGB LED (base that it is Cree LED PLCC4) and tried to found in the datasheet the information about the resistor(s) needed. Than when I will get back to the FabLab I can check exactly what model we have in storage. At least I will know (more or less) where to search for the information that I need.
Went through a datasheet. Did not found what I was looking for...
Forgot that what I am looking for is not directly an R but V and I. 

R = (V_source - V_LED) / I

Trying out a new mkdocs addon too:

\[ R = \frac{V_{source} - V_{LED}}{I} \]

So if my source is 5V; the forward voltage is 3.1V and I is 20mA

\[ R = \frac{5 - 3.1}{0.02} = 95 \Omega \]

And for RGB I need to do this calculation 3 times for each pin.

Discovering Anode & Cathode LEDs.

explains it really well: With a common anode you connect the anode to the +5v and each individual LED to a resistor each. Connect that resistor to an output pin. Then a write LOW to that pin will turn the LED on and a HIGH will turn it off. This is called current sinking. With a common cathode you connect the cathode to ground and connect each LED's anode through a resistor to the output pin. Then a HIGH turns it on. This is called current sourcing. Here is a longer video explanation if needed.



Fun !
I have an RGB LED but no indication of serial number...
I am parsing through digikey to see if I can found one that looks alike.

In the end Axel came and I asked.

The RGB LED that I will be using is the SW2812
This thing has a complicated pin layout (not really after you understand). Fortunately there was an example circuit at the end of the manual with what resistors and capacitors to use.

Libraries that can work with this LED :

Button

For the button I am going to use the F3SN-3112P. From all the buttons we have, it has the best feeling when pressing down. And the best click sound.

A point that Henk pointed out is if the XIAO ESP32-S3 has pull-up resistors or not. A quick search in the manual says that GPIO0, 3, 45 and 46 have a WEAK pull-up/pull-down resistor.

I asked Henk if I should stick with the weak one or if I should setup my own.

While waiting lets read some stuff.

In the end I decided to add my own pull up resistors.

Screen

I have a 16x2 QAPASS LCD I2C MODULE and also a I2C OLED Display but unfortunately I lost too much time with figuring out how to connect together all the previous components.

Schematics Editor

My final schematic:

Schematics

Components and their footprints (most of them from FabAc Library):

Footprint

PCB Editor

Now that the Schematics is done I need to figure out how to connect all this together. While doing that, sometimes I rearranged the pins so it simplifies the layout of the routes.
My head start to hurt.
So many cross overs...

I HAVE FOUND A WAY!!!

I just need to use 0 Ohm resistors to go 3D.

I am a genius. I just need to figure out where to put them.

Well.
Fun.
I just discovered that KiCAD Board setup is per project... So now the channels width settings have been updated, I can start rewiring...

For the Cut I wanted to make little fingers for the button but I struggled so much with connecting everything together that I wont do that anymore. Otherwise I would us up all our stock of 0R.

Editor

Showing this to one of my colleague he had some issues with it (& some issue that I have found later):

  1. I should never use 90° angles in circuits. It has a bad effect on the courant.
  2. I should put filaments close to each other to cancel out the magnetic field created by the passing courant to limit the noise generation.
  3. I should change the direction of the sound pin. But that is easy to correct.

THERE IS AN AUTO TRACER ?!?!
Should try it out to see if it does a better job than my brain. But using that would have saved time, that is for sure.

Another note from regional meeting: using cable (jumper wire) on the other side of the PCB to make it a two sided PCB.

Learning Outcome

This was a first for me.

The schematics is quite fun, until you need to find the correct footprint. That part can be sometimes complex. Otherwise I really enjoyed that part.

The PCB editor on the other hand...
That is quite a headache. To wire everything together is quite a challenge.

Assignment Check

  • group assignment:
    • use the test equipment in your lab to observe the operation of a microcontroller circuit board
      • Done
  • individual assignment:
    • use an EDA tool to design a development board that uses parts from the inventory to interact and communicate with an embedded microcontroller
      • Done
    • extra credit: try another design workflow
    • extra credit: design a case for it