10. Output Devices

Hero Shot of the Week

Summary

Disassembling stuff to create new stuff. This week we saw output devices. I played around with an OLED screen, audio output (kinda) and LEDs.

Work Process

Calendar

Date	To be done	What was done
Thursday	- 10h local	- local
Friday	- FabLab normal work	- 3D printer calibration - laser cleaning
Saturday		- OLED screen testing - socializing (needed some friendship energy)
Sunday		- further OLED tests
Monday		- PCBs - weird LED panel
Tuesday	- FabLab normal work	- emails - documenting
Wednesday	- 12h Local - 13h Regional - 15h Global

Safety

• ~1 mA: OK
• ~10 mA: shock, contraction
• ~100 mA: fibrillation

Capacitor Charged / Discharged status !

Introduction

Henk made an introduction based on Erwin's slides.

• LEDs
  • Anode VS Cathode
  • 1 color VS RGB
  • PWM (for discrete) VS microC (for digital)
• MOSFET VS BJT
• Displays
  • 7-segments
  • Dot-matrix
  • OLED
  • LCD
• Solenoid
  • "contactless" switch
• Speaker
  • coil + magnet + membrane
  • piezo
• Motors
  • DC
    • H bridges
  • Servo
    • DC Motor + gearbox + sensor (for position ctrl)
  • Stepper
    • control via phased signals
    • more steps = more precision

Brake

Some fun videos that where shared while talking about output designs. It all started with motors doing funny noises that could be converted into music.

Flopportron <- backup link

Science Vs. Music <- backup link

Tesla Coil - Thunderstruck <- backup link

Happy Holidays from ShopBot 2010

Measurements

In total (we) they measured three different things.

A motor

LED Strip

ESP32

My work

Screens

OLED

My first step was to create a holder for this screen. I went through different versions as I sometimes miss calculated stuff. I wanted to do this first so I would feel more comfortable with handling this screen.

I did not have any 1x4 socket so I dremelled off 3 pins of a 1x7 socket. I did that on a via socket. Now that I know it works I can do it on one that has his legs going to the side.

After that I wanted to create a PCB. And the original design that I wanted was too complicated. I could not figure out the traces layout. Even AI did not give me satisfactory answers. So I went with a simple design with the belief that I can change the text direction in software. I have no clue if that is something that is possible.

My first issue is that I have no clue what type of oled display I have. I should ask my colleague when monday comes.

Anyways, I followed this Tutorial as I brought home the different components.

First try did not work as I did the 128x64 screen. Doing the I2C scan revealed that I should have a 128x32 screen instead. When I tried that code it worked.

It is quite a complete guide.

So I did my PCB for connecting the OLEd. I also added the pins to the holder so that it can be used with the breadboard. For that I printed sideways. Of course now the hole for the screws are too wide...
When they were perfect previously printed horizontally...

For the PCB I also made a miscalculation in the position inside the CNC. So half of the PCB side is missing. It was also not totally flat (at the edge of my copper plate) so one of the sides traces was not cut properly (see photo).

So I tested for short circuits and it is ok. As it was symmetrical I soldered the ground to that side. So it should not create any problem.

The final pin design works just fine. I also added a pad that previously protected the pins of an input device to support the display and to push down onto the PCB as it is fixed with friction, instead of a screw as the other input devices.

I2C Scanner

//
#include <Arduino.h>

// I2C Communication
#include <Wire.h>

// ---------- Function declaration ----------
// I2C Scanner
void I2C_Scan(); //I2C Scanner, no Pin required, To check I2C devices connected to the board

// ---------- Setup ----------
void setup() {
// put your setup code here, to run once:
Wire.begin(); // Initialize I2C communication

Serial.begin(9600);   // Initialize Serial Monitor
while (!Serial) { delay(10); } // Wait for serial console to open!

}


// ---------- Loop ----------
void loop() {  

I2C_Scan();

}


// ---------- Function definitions ----------
// ---------- I2C Scanner
void I2C_Scan() {
byte error, address;
int nDevices;
Serial.println("Scanning...");
nDevices = 0;
for(address = 1; address < 127; address++ ) {
    Wire.beginTransmission(address);
    error = Wire.endTransmission();
    if (error == 0) {
    Serial.print("I2C device found at address 0x");
    if (address<16) {
        Serial.print("0");
    }
    Serial.println(address,HEX);
    nDevices++;
    }
    else if (error==4) {
    Serial.print("Unknown error at address 0x");
    if (address<16) {
        Serial.print("0");
    }
    Serial.println(address,HEX);
    }    
}
if (nDevices == 0) {
    Serial.println("No I2C devices found\n");
}
else {
    Serial.println("done\n");
}
delay(5000);          
}

OLED

//
#include <Arduino.h>

// I2C Communication
#include <Wire.h>

// For the OLED Display
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
//#include <SPI.h>
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 32 // OLED display height, in pixels
#define OLED_RESET     -1 // Reset pin # (or -1 if sharing Arduino reset pin)
#define SCREEN_ADDRESS 0x3C ///< See datasheet for Address; 0x3D for 128x64, 0x3C for 128x32
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
#include <Fonts/FreeSerif12pt7b.h>

// ---------- Function declaration ----------
// OLED Display
void OLED_STAR(bool initialize); //function to initialize the OLED Display
void OLED_DISPLAY(); //function to display the data on the OLED Display

// ---------- Setup ----------
void setup() {
// put your setup code here, to run once:
Wire.begin(); // Initialize I2C communication

Serial.begin(9600);   // Initialize Serial Monitor
while (!Serial) { delay(10); } // Wait for serial console to open!

// Initialize the OLED Display
OLED_STAR(true);

}


// ---------- Loop ----------
void loop() {  

OLED_DISPLAY();

}


// ---------- Function definitions ----------
// ---------- OLED Display
void OLED_STAR(bool initialize){
// SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
if(!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Don't proceed, loop forever
}
// Show initial display buffer contents on the screen --
// the library initializes this with an Adafruit splash screen.
display.display();
delay(2000); // Pause for 2 seconds

// Clear the buffer
display.clearDisplay();
}
void OLED_DISPLAY(){
// Clear the display buffer
display.clearDisplay();

// Text Settings
display.setTextSize(1); // Normal 1:1 pixel scale
display.setFont(); // Choose a font
display.setTextColor(WHITE); // Draw white text
display.setCursor(0, 0); // Start at top-left corner
display.setRotation(2); // Rotate the display 0 to 3 times 90 degrees

// Display static text test
display.print("Hello, World!");

// Display the buffer contents on the screen
display.display();
}

Qapass

It seems like it has an I2C 1602 LCD Controller preinstalled on it.

I also tried to follow the Tutorial from the same source but it seems that I have a library issue. When I check the github page of the library that the page wants you tu use it is said that it was archived and moved to gitlab, but the gitlab page is not found.
Wow
The story behind this library is quite something

So I asked in Mattermost if there is an alternative for this library. Adrian suggested that I go check out Niel's code. His code uses the LiquidCrystal_PCF8574 library.

As this was getting more and more complicated when I already had the OLED display working I will instead focus on my final project...

Other Links:

• LCD Displays
• I2C Liquid Crystal Display

LEDs

Weird LED

So there is this LED background light that was resourced from a broken scale balance. Tested with the multimeter and all leds are working. There were little resistor locking stuff on the PCB so I asked one of my colleague if he nows what it is. He told me that they are 130 Ohms resistors. With further testing we come to the conclusion that the LEDs are in parallel. Than I soldered two cable on the board to make it easier to work with.
When I gave it power the surprise came.

More exactly the witchcraft...

So the LED that has the ground will light up the brightest with all of them still lighting up.

So they are neither only in series or only in parallel. But some witchcraft connectivity that allows you to light it up with a brightest spot by playing with the ground.

Ok. So I asked Nicolas and he helped me to figure it out. I was doing Case 1, so putting the ground at the end of one of the LEDs. The other LEDs light up as it was short circuited with 2 resistors instead of one.

After this I resoldered my ground onto the right side of one of the resistors. And now all the LEDs light up with the same intensity.

RGB

• DataSheet WS2812
• ESP32: FastLED vs. NeoPixelBus vs. NeoPixel Library
• RGB Matrix project - Fab23

Charlieplexing

• Charlieplexing - Reduced Pin-Count LED Display Multiplexing

How to reduce pin count.

One cable can be used as cathode or anode alternatively (LED are directional)

A video to explain it more visually:

A quick look at Charlieplexing <- backup link

Audio

I also wanted to test out audio. But I wanted to do something modular. I do not have the time to create some ampli-op (and other audio stuff) right now so I wanted to have the option to add it later on. So I thought of a design where I can short circuit if I want to and also add some addon if I want to.

As I did not have any audio component, and my colleague who has all the stocks is not present today (general strike today, monday) I DIY it. So I took an old headset that was left here in the FabLab and nobody wanted to use and took it apart.

Than I started working on my PCB design. I have some Screw Terminal but did not know the footing that went with it...

So I asked on mattermost and with the help from there (thx Adrian) I tried to work out with something that has the same footing.
Somehow I still messed up...

Second PCB (right) was good.

While I did my second PCB I broke a mill head. I installed it, launched auto Z calibration, and it broke. The head went down down (into goblin town) and at one point it snapped. I have no clue why the auto calibration did not work...

In the meantime I also did some shopping.

I needed a female jack and a sandwich.

(be kind with your judgement)

After a lot of soldering (and some finger burning), my composition work. So at first test I did not work.
Why ?
Because I forgot the jumpers of the extension pins...

So it work when it is plugged into a laptop for sound. Now I just need to test it if it also works with a microcontroller

Now that I think on it. Isn't it better for audio to use 1 copper cable instead of copper cable made up from smaller cables ?

The hard part to play music is that for simple one it can be stored in a string form in the code. For more complex song you need to incorporate an SD card into the system where you can store your music.

• Simple Audio system
• Playing popular songs with Arduino and a buzzer
  • GitHub library
• Espressif Systems Audio Development Framework - GitHub

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Learning Outcome

Do not burn your finger while soldering.

Output devices can be fun, and somehow I found them easier than input devices (but maybe I only tested the easy ones...).

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Digital Files and Links

• Fluid Simulation Pendant
• OLED KiCAD
• OLED FreeCAD + STL
• Audio KiCAD

Other Reading

• Field Oriented Control with (almost any?) Stepper

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Assignment Check

• group assignment:
  • measure the power consumption of an output device
    • Done
• individual assignment:
  • add an output device to a microcontroller board you've designed, and program it to do something
    • Done

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