Naldi Carrión

Individual Assignment

Selecting the output device

With my instructor support, we review the components that I'm gonna need for my final project in order to decide which output could be the starting point. So I decide to start with a Servo motor that I'll probably use to open the hidden shelve. The following picture show the potential devices that I would use for my final project. I would use 2 Servo Motors, so the option could be to fabricate one or two boards. I decide to fabricate one.

Board Components

By acknowledging that servo motors function with 5V and common power supply sources provide 12V, we select the following components for this main board. It consists of the following:

1. One terminal block 2x1
2. Regulator LDO 5V 1A
3. Male connector header 2x3
4. Male connector header 90° 1x3 (GND+2DIO)
5. 2 Servo Motors
6. Capacitor 1uf

Regarding the Low Dropout Regulator, we review technical information here , and in summary its key technical characteristics are the following:

1. It has 4 pins (IN, GND, OUT)
2. Requires an output capacitor to maintain stability
3. Dropout Voltage 500 mV
4. Max Input Voltage 26 V
5. Max Operating Temperature 85 °C

Schematic Development with KiCad

We select KiCad to design our board, taking into account that when working on schematics, we need to be careful with labeling each component in/out or GND adequately. Further we need to phycally recognise each component, because we made a mistake on regulator pins order, so when working on PCB editor traces were crossing, and took me sometime to understand the problem.

This is the schematic where you can see all the components. You can download Schematic design file and the PNG file here.

PCB Designing

To obtain PCB design and fabricate it, we need to take the following steps:

1. Select the PCB Editor File from the KiCad Principal Menu.
2. Update PCB from Schemnatic option located at Tools Menu on PCB Editor.
3. Set track sizes (width) and appereance (material) option located at Edit Board SetUp Menu. Here we set 0.4 for traces width and 0.8 for ground and energy traces.
4. Setup constraints option located at Edit Board SetUp Menu. The most important it is to setup cleareance at 0.4 to no exceed the end mill diameter
5. Start drawing the traces selecting width and material correctly

This is the pcb design where you can see all the components. You can download design file and the SVG files here.

PCB Machining Setting

To fabricate PCB design we use SVG files applying following steps within FabModules Software:

1. Upload SVG Board file.
2. Convert SVG image inverted it using 1000dpi.
3. Set mill traces (material) using 1/64" end mill (select 2 as offsetting number).
4. Calculated Mill raster 2D.
5. Visualize the image selecting width and material correctly
6. Send file as final step
7. Applied same steps for Cutting Edges but use 1/32" End Mill

The machining was made with a Modela MDX-20. I have got the following problems while machining:

1. I machined a previous used board, and it seems that it wasn't attached firmly and moved while milling, so I had to stop the machine to avoid a broken end mill (photo 1)
2. I made a mistake while stablishing coordenates when cuting edge layer, and affect my traces (phot 2)

PCB Soldering

To proceed with soldering I fix the PCB with double contact tape. Thus, we can avoid any movement when tin soldering

1. I started soldering the small components
2. I kept as strategy was to fix one (pin) of each component and then the others
3. At The final step I soldered the terminal block, because it needed pcb perforations

I have a major problem with the terminal, because when selecting the componnets at the schematic, I didn't choose the correct model, and the distance between pins was shorter. Thus, after perforating the PCB the connector didn't fit. Thus I decided to fold the pins and tried to solder them. However the space between the capacitor and terminal's pins was short, and while soldering the cooper layer sliced. The following photo registered the problem. Thud, I have to machine another board and use new components

The Programing

For functional testing I used a modified coding provided by Adrian Torres and follow this Arduino IDE coding:

• Open Arduino IDE software.
• Connect the serial port to the board.
• Copy the original code provide by Adrian Torres.
• I only replace the pin number that correspond (Pin 3) at the begining, setting the output like shown in the code shown below:



	
#include 

Servo myservo;  // create servo object to control a servo
// twelve servo objects can be created on most boards
	
	
void setup() {
  myservo.attach(3);  // attaches the servo on pin to the servo object
}
	
void loop() {
  int pos;
	
  for (pos = 0; pos <= 180; pos += 1) { // goes from 0 degrees to 180 degrees
	// in steps of 1 degree
	myservo.write(pos);              // tell servo to go to position in variable 'pos'
	delay(15);                       // waits 15ms for the servo to reach the position
  }
  for (pos = 180; pos >= 0; pos -= 1) { // goes from 180 degrees to 0 degrees
	myservo.write(pos);              // tell servo to go to position in variable 'pos'
	delay(15);                       // waits 15ms for the servo to reach the position
  }
}



• The #include see Source file inclusion, in this case identifies Servo.h file from Arduino IDE library which need to be compiled and link with the code.
• The void setup is a function that contains the initialization of the component that I want to control (output), or that will send me information (input)
• myservo.attach, attach the Servo variable to the pin 3 setting it as an output
• void loop allows to repeat the code that follows over and over again
• int pos;, it is creating a variable called position, which limits will be set in the following code lines
• for (pos = 0; pos <= 180; pos +=1), for statement is used to repeat a block of output behave enclosed between curly braces. In this case, we are establishing position variable to move from 0° to 180°
• myservo.write(pos); will call the variable set in the previous code line, in this case to move in relation to "for" statement from 0° to 180°
• delay (15) will set the time that will took the servo movement to go from 0° to 180°
• for (pos = 180; pos >= 0; pos -= 1)In this case, we are establishing position variable to return from 180° to 0°
• myservo.write(pos); will call the variable set in the previous code line, in this case to move in relation to "for" statement from 180° to 0°
• delay (15) will set the time that will took the servo movement to go from 180° to 0°
  

  The following photo shows all system connection to test. I used XIAO RP2040 from Week 8 to test the board and the output device (Servomotor)

  
  

  The final test was made runing the conding Arduino IDE and using a variable energy source, like shown in the following video

  You can get access to the servo code here.

  Reflections

  1. KIDCad software has really friendly interface, even for a newbee on electronics like me. I reocmmend to take a look to KidCad Tutorials
  2. It is very useful to review previous FabAcademy's students work that bring us some information regarding previous coding and tips about problems or common mistakes that we could repeat. And it is recommendalbe when using codings, review the assignment's files, because sometimes what was included on web pages have some missing coding lines
  3. For every further electronic design it is recommendable to work on PCBs that we'll need for our final project. Thus, integration will be less complex
  4. The noise produce by the servomotor shows that the soldering needed to be reviewed, due to false contact