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- Steps:
8. Electronics Design
Electronic circuit designing involves the selections and interconnections of physical devices, for
different purposes. It is important to define the requirements that you are going to use such as: resistors,
capacitors, buttons, leds, voltage regulator and one of the most important things the microcontroler (brain).
For this week assignment I will be creating my own pcb using Kicad and an ESP32-wroom32.
Group Site
If you want to read the Group Page, Click Here.
For this group assignement we had to test different equipment to know more about electronics and a microcontroler operation.
- Equipment (hover for more info):
There are different microcontrolers boards depending on the project your making. The most common ones are:
Arduino, RaspberryPi, ESP32, PIC, etc.
A power supply it is used to power up the circuits you build, depending on you requierements AC or DC.
It is used for meassuring voltage, current, resistance, capacitance, continuity, etc. Basically is a test tool
to meassure different values. You can change it mode by switching the dial to its position and verify the input jacks.
Voltage
If you want to meassure Voltage verify the dial is in V (DC or AC) and connect it in parallel in the part you want.
Current
For current change the dial to A and the input jack. For meassuring you have to open the circuit and make a series conection.
Resistance/Capacitance
In the case of resistance and capacitance when you dont know the value you only have to touch it with the 2 probes.
Continuity
The same thing as resitance but instead of giving you a value it will emit a beep when the circuit is closed.
It is used to visualize/analyze the behavior of the electronic signals. Commonly used for fixing mistakes, debugging and check the signal integrity.
It produces different type of waveforms (sine, square, triangle), used to test different signals conditions.
One of the most important parts of the components is the datasheet, in here you can find the lenght of the components, voltage, current,
schematics and everything you need for designing your circuits.
Let's try out with some test
For this part I will make a sampling on a digital system for later obtain the original signal.
For using most of the equipment from above I will use an arduino to obtain an analog reading (wave sign) from the function generator in the Pin A0 in an Arduino. Make a vector to store data. Send them to matlab by serial port to generate the graph in the oscilloscope.
Code in arduino
const int analogInPin = A0;
int k=49; // Number of samples
int sensorValue[50]; // Vector to storage data
int i;
unsigned long ts = 2.5; // Sample time mseg
unsigned long TiempoAhora = 0;
//sensorValue = 0; // value read
void setup() {
// initialize serial communications at 9600 bps:
Serial.begin(9600);
}
void loop() {
for(i=1;i < =k;i++){
TiempoAhora = millis();
sensorValue[i] = analogRead(analogInPin);
// wait n milliseconds before the next loop for the analog-to-digital
// converter to settle after the last reading:
while(millis() < TiempoAhora+ts){
// espere ts milisegundos
}
}
// print the results to the Serial Monitor:
for(i=1;i < =k;i++){
Serial.println(sensorValue[i]);
delay(5);
}
Serial.end();
}
Code in MatLab
function Matlab_Arduino(~)
% Matlab + Arduino Serial Port communication
close all;
clc;
frecuencia = 50;
periodo=1.0/frecuencia;
numero_muestras=40;
% Se tomaran 20 muestras por ciclo de la señal se graficaran 2 ciclos
% Total de muestras 40
% Con un tiempo de muestreo del Arduino cada
delay_arduino=2*periodo/numero_muestras;
y=zeros(1,numero_muestras); %Vector donde se guardarán los datos
x=(0 : 1: numero_muestras-1)*delay_arduino;
t=delay_arduino*(0:1:numero_muestras-1);
disp('fijar delay de arduino');
disp(delay_arduino*1000);
z=input('listo ???');
%Inicializo el puerto serial que se utilizará
delete(instrfind({'Port'},{'COM5'}));
puerto_serial=serial('COM5');
puerto_serial.BaudRate=9600;
warning('off','MATLAB:serial:fscanf:unsuccessfulRead');
%Abro el puerto serial
fopen(puerto_serial);
%Declaro un contador del número de muestras ya tomadas
contador_muestras=1;
ylim([0 5.1]);
xlim([0 numero_muestras]);
%Bucle while para que tome y dibuje las muestras que queremos
while contador_muestras < =numero_muestras
valor_potenciometro=fscanf(puerto_serial,'%d')';
y(contador_muestras)=(valor_potenciometro(1))*5/1024;
contador_muestras=contador_muestras+1;
end
%plot(x,y);
plot(x,y,'-o');
grid on;
figure;
sig=2.5*sin(2*pi*frecuencia*t)+2.5;
%plot(t,sig);
plot(t,sig,'-o');
grid on;
%Cierro la conexión con el puerto serial y elimino las variables
fclose(puerto_serial);
delete(puerto_serial);
clear all;
end
Designing
There are different softwres for designing circuits such as:
As I mention before I will be using KiCad. When you open it you find this main page where you can create a new project, open schematics, etc.
For the use of ESP32-wroom32 is used for base this ESP schematic.
My board wil have out pins for any use in the future, as well as power pins (+5v, 3.3v and ground) y also group some of the most common pins as power, I2C, UART, for testing adding a Neopixel and a button.
First it is important to install the library and footprints of the components we have available in FabLab Puebla.
Steps to add library
Open Symbol Library
Open Footprint Library
Configure Paths
Schematic
Interface
First we can se the work frame where we can add the components and its conections.
On the right bar are all the components, wire, labels, text, all you need for your Schematic.
And some more options on the top bar as: creating a PCB, zoom, mirror, rotation, etc.
Symbols/Shortcuts
In all the left side bar we can add items by clicking them or using its shortcut.
- Shortcuts:
Components
By clicking A or the button it will appear the window where you can find all the components schematics,
footprint, component name and datasheet.
*Note: It is importantto verify the footprint of your component.*
Components I use
- List:
Rules
On the navigation bar -> Inspect -> Electical Rules Checker -> Run ERC
Here you can find all you mistakes on your conections, design, power supplies, etc.
Final
So in my PCB I start adding the microcontroler I will use, in this case is the ESP32-wroom32, after that I investigated about the output pins, wich ones can I use, boot, reset, etc. Having on base this schematic. Afet knowing all the pins, I started by adding the buttons, resistors and capacitors. For testing my board I add a Neopixel and a button to make some actions. Finally we can add our pin headers for comunicating to other future devices. I joint the most common ones together such as I2C, UART, Programing and Power. In the case of the power I added a +5v of input in case of external battery with 2 voltage regulators to (5v and 3.3v).
If you don't have mistakes or the mistakes/warrnings don't affect your designing like ports not connected or something else, you can continue by routing all the PCB and giving it the final shape. On the top bar you find the Open Board to start.
PCB
Once you're creating a new PCB it appears this window:
- Steps:
By adding all the components the software makes and invisible autowire (green), this shows where you have to connect everything. First I started to make this lines straigh to the pins of the esp, so having the esp on the center of the board is the most optimal in this case. I always added the capacitor, led and resistor to his button like a single package. Lastly I put the pin headers on the border.
For the wire I choose a clearance of 0.4 and a track width of 0.5. This rules is fot the current that the board will support, I use 0.7 for data, 3.3v and ground. And for the +5v of input I put a 1mm track width.
For the border I use 1mm because the tool was of this diameter so for the software (mods) to generate the contourn correctly it cas to fit in.
Once all is complete we got the final PCB design after many attempts.
3D perspective
Once you have done all the conections you can preview a 3D image of your Board to see how it will finally look.
Export
We have to export it as an SVG
Once we have the both files we can upload them into mods to get de .rml for the Roland milling machine.
Fabrication
In this case instead of uploading a png file, right on top we upload the SVG format.
We modify the same parameters of milling and cutting, in my case I will lower the speed to 3 mm/s, 2 offset and
a tool diameter of 0.3 mm. I change this because some of my components have smaller paths.
Having this 2 different files for milling and cutting.
Case
For creating a case to the new PCB made I used Solidworks for the design, Cura for getting the g-code and print it in an
Ender.
- Steps:
Slicing in cura
Like we dont care about the resistance we only give a 8% of infill gyroid with Raft adhesion.
Final case
Soldering
For soldering the firt thing to do was getting all the components.
- Components (hover to see them):
Once we have all the components and the schematic in hand we can start to solder. After a while we got all the board done. To verify all its good we check continuity with the help of a Multimeter.
Test code
I added a button (GPIO4) and a Neopixel (GPIO2) for testing that the board works I will be changing its color by pressing the button.
Steps:
Code
#include
#define PIXEL_PIN 2
#define NUM_PIXELS 1
#define BUTTON_PIN 4
Adafruit_NeoPixel pixels(NUM_PIXELS, PIXEL_PIN, NEO_GRB + NEO_KHZ800);
// Define colors
uint32_t colors[] = {pixels.Color(255, 0, 0), // Red
pixels.Color(0, 255, 0), // Green
pixels.Color(0, 0, 255)}; // Blue
int current_color_index = 0;
void setup() {
pixels.begin();
pinMode(BUTTON_PIN, INPUT_PULLUP);
}
void loop() {
if (digitalRead(BUTTON_PIN) == LOW) { // Button is pressed
changeColor();
while (digitalRead(BUTTON_PIN) == LOW) { // Wait for button release
delay(10);
}
}
}
void changeColor() {
current_color_index = (current_color_index + 1) %
(sizeof(colors) / sizeof(colors[0]));
pixels.fill(colors[current_color_index]);
pixels.show();
}
Files
