Week 6- Electronics Design

Overview

For this week we have two assignments:

Group assignment

to use the test equipment in our lab to observe the operation of a microcontroller circuit board. minimum, check operating voltage on the board with multimeter or voltmeter and use oscilloscope to check noise of operating voltage and interpret a data signal.

Individual assignment

Redraw one of the echo hello-world boards or something equivalent, add (at least) a button and LED (with current-limiting resistor) or equivalent input and output, check the design rules, make it, test it.

My Assignment Steps:

Step (1):Design The board (Sch- PCB Layout)

Step (2):Milling and solder the board.

Step (3): Test the board and program it.

The Process

Individual Assignments

This week is a complementary work to week 4 where we learned the Electronics Production, Now it is time to make our own PCB :).

Choose your Software

When it comes to electronics design, there is a huge number of software that we can use Eagle, EasyEDA, Kicad.. etc.

As an electronics engineer I'm pretty familier with bunch of them and my recommendation is either to use Eagle or Kicad

Kicad

Kicad is a cross platform open source Electronics Design Automation Suite.it's a little bit complex comparing to Eagle but, it's a full package program in which you are gonna find everything you need. for me it's my no.1 choice.

Kicad tutorials.

Eagle

EAGLE is a flexible and expandable EDA schematic capture, PCB layout, autorouter and CAM program. EAGLE is popular among hobbyists because of its freeware license and rich availability of component libraries on the web.

Eagle tutorials. he use an older version but, the difference is only in the GUI.

for the Redrawing assignment I' gonna use Eagle but, for my own board I'm gonna use Kicad.

Download Fab-library

Step 1:

you can find a fab-library with all the inventory component Here. download it then create a folder wherever you want the .lbr file to be kept.

Step 2:

open Eagle form option choose Directories

modify the libraries path location to tell Eagle exactly the folder location and name where it will find the library.

The path must look like -> $EAGLEDIR/lbr:/Users/yourUserName/FileLocation/LibName

Step 3:

finally from Libraries right click on lib-name andd choose use all.

Board Design

Eagle has two windows that you use simultaneously to design a board:

Schematic (.sch) - logical components

A schematic in electronics is a drawing representing a circuit. It uses symbols to represent real-world electronic components.

Board Layout (.brd) for the actual board that we mill

The board layout shows how the electrical components and traces will be laid out on the board.

you need to keep both open all the time as closing one view while the other view is open (and making edits) will break the link between the two

Schematic Design

I choose to redraw the Attiny45 circuit and add an indicator LED for power. plus an switch as a sensor to start the main led to blink.

First I add all the component I'm gonna use:

1 x Attiny 45.

1 x (2x3) pin header for AVRISP.

1 x (1x6)pinheader for Rx,Tx,VCC,GND.

1 x 1 uF Capacitor.

1 x Red LED.

1 x Green LED.

1 x Slider Switch.

2 x 10k Resistor

1 x 1k Resistor

2 x 499 Resistor

Then it's time to wire the circuit. There are two ways to connect components in a schematic:

You can connect the components with a wire (also called a "net" in Eagle). This may make connections obvious at first, but can get really messy quickly as nets cross over each other.

You can also name the nets attached to components that need to be connected by the same name. Eagle will ask you if you want them to be connected. (Say yes).

I wire my circuit using the second methods.

PCB Layout

Switch to PCB layout, the components you just added will be jumbled up in a corner with yellow unrouted traces attached.

Start move, organize, route the component as you need.

Design Rule check

After designing our board we need to check that the endmill we are using (1/64 usually) is able to go between and around all the traces so the machine is able to cut successfully the board.

a mill-bit with the diameter of 1/64 inch (~16 mil) is used; So I opened the DRC from The "Tools" menu. Then in the "Clearance" tab, I wrote "16mil" to all the fields there.

I came up with 4 errors and 2 warnnings. time to fix the circuit :)

To make sure all is good I run DCR one more time and it came out with no error as you can see in the left corner.

Hide all the layer except for the TOP in order to export the circuit as PNG.

(file -- export -- image),settings should be MONOCHROME and 500 DPI - this will export a image with white traces.

The final output ready to edit in GIMP.

Edit image using GIMP

crop the image, add text if you want, from image choose Flatten image and export as PNG.

for the outline create a new window with the size of the circuit + 5px for the outline, from select choose all then -> border with 5px , finally choose the bucket fill tool to coler the border with black and export as PNG.

Milling and solder the circuit

following the same steps we did in Electronics production week I was able to solder and mill the circuit.

I use the multimeter to verify the continuity of the tracks and to check the operating voltage on the board.

Testing the circuit

1) The Code:

The idea of the board is really simple we have a switch that work as an input to the Attiny 45 in the case it's high we aria-control any kind if output to be sent to our Led.

for rapid test I choose to write the code in ArduinoC and to use Arduino IDE to upload the code to my board.

#define LedPin 3
#define SwitchPin 2

void setup() {
  pinMode(SwitchPin,INPUT);
  pinMode(LedPin,OUTPUT);

}

void loop() {
  boolean switchState;
  switchState=digitalRead(SwitchPin);
 
  if(switchState){
    digitalWrite(LedPin,HIGH);
  }
  else{
    digitalWrite(LedPin,LOW);
  }
}

2) Program The board

Time to focuse now !!

we will going to upload the code to our board using arduino IDE and using arduino as our programmer as we did in Electronics production week

1- Install Attiny library support for Arduino IDE

go to File > Preferences > Additional Boards Manager URLs field near the bottom of the dialog box.

paste the following URL, then click ok

 https://raw.githubusercontent.com/damellis/attiny/ide-1.6.x-boards-manager/package_damellis_attiny_index.json

Tools >> Boards > Board Manager > search for attiny and then choose to install it.

2- Prepare the arduino Board as a programmer

Under File > Examples > ArduinoISP you can find the code you need to upload to your Arduino in order to transform it into an ISP

upload the code to the arduino board.

After programming the arduino, connect a 10 uF capacitor between RESET and GND.

3- Upload the Bootloader

you can then connect Arduino with your board. the configuration for connecting the Arduino is down here.of course VCC connected to 5V and GND connected to GND.

slave reset: 10
MOSI:        11
MISO:        12
SCK:         13

File > new

Tools > Programmer >Arduino as ISP

Tools > Boards > ATtiny 25/45/85

Tools > Processor > ATtiny 45

Tools > Clock > internal 8 MHz

Tools > Burn bootloader

4- Upload the Code

Upload the code to the board then remove the connections.

Final Project

Well first spiral it's all about hardware design and embedded programming by the end of it I should be able to :

Detect the clapping sound.

Control Aincrad lighting systems.

so without further ado let's jump to the steps.

ELECTRONIC CIRCUITS (PCB) DESIGN AND FABRICATION

I need to design 3 board for Aincrad:

The Master board that control the sound sensor and the lighting system
Sword lighting board 5 total.
Sword lighting - Master interface board.

1) Aincrad Master Board:

Specifications (Electrical)

Output drive capacity = 5V.
Input signal from any sound sensor and ""bluetooth in future""
Output signal to lighting system consist of 3 RGB led/castle body and 5 Led for each sword.
PWM channels to control the lighting system and the "motor in future"
Assume in all power calculation that copper layer is only “1 oz thickness”

Depend on this specification I could use either 2 Attiny-family board one for the input and the other for the output and let them communicate with each other through serial bus. or an atmega-family board with all in on system.

I go for the second option in order to save space and for more neatness in the final connections.

Specifications (Mechanical)

Use 32-pin TQFP For Atmega328p-au know more about it from datasheet
Board dimensions with curved angels

2) Block Design

3) Schematic Design using Kicad

I divided the master board into 3 main functioning citcuits

Atmega328p-au circuit + interface
Sound sensor circuit
Castle RGB lighting circuit

Atmega328p-au circuit + interface
your number one friend through this step is the datasheet. So from the Atmega328 datasheet I was able to know:

Atmega328p-au specifications

32K bytes of in-system self-programmable flash program memory

1Kbytes EEPROM, 2Kbytes internal SRAM

Two 8-bit Timer and One 16-bit Timer/Counter

Six PWM channels

8-channel 10-bit ADC in TQFP

Communications protocols USART, SPI, I2C.

32 programmable I/O lines in TQFP

Operating voltage: 2.7V to 5.5V and speed up to 16MHz.

Circuit Components

1* Atmega328p-au

1* 16MHz crystal

2* 22pf ceramic capacitor

1* 10uf ceramic capacitor

1* 10 kohm resistor

1* 499ohm resistor

1* green led

1* 2×2 pinheader

1* 1×3 pinheader

1* 2×3 pinheader for ISP

1* 1×6 pinheader for FTDI

schematic design for Atmega328p-au

Sound sensor circuit

SPU0414HR5H-SB MIC for sound sensor specifications

from SPU0414HR5H-SB datasheet

Up to 20dB of Gain
Maximum supply voltage 3.6V
Maximum Low Current 220uA
Signal to Noise Ratio SNR 94 dB SPL @ 1 kHz, A-weighted
RECOMMENDED REFLOW PROFILE Peak Temperature (TP) 260°C

This specification means I will need to use a voltage regulator with the sensor in order to convert the 5V power to 3.5V

Circuit Components

1* Mic MEMS analog SPU0414HR5H-SB

2* 0.1uf ceramic capacitor

1* 10uf ceramic capacitor

1* 1kohm resistor

1* LM3480- 3.3V

SPU0414HR5H-SB circuit from datasheet, I choose to design my circuit with Max Gain (20db).

SPU0414HR5H-SB pin configuration

So now in order to design the circuit I need to choose a voltage regulator to convert 5V power to 3.5V I go with LM3480 Low-Dropout Linear Voltage Regulator

LM3480 Linear Voltage Regulator specifications

from the datasheet

Input Voltage Range: up to 30 V
3.3-V, 5-V, 12-V, and 15-V Versions Available
100-mA Ensured Minimum Load Current
SOT-23 Package

Vout= Vin-1.5 which means :
Vout= 4.8-1.5= 3.3V

Knowing the detailed design procedure from datasheet

schematic design for sound sensor

Castle RGB lighting circuit

Cree PLCC4 3 in 1 SMD LED specifications

from RGB LED datasheet

Size (mm):3.2 x 2.8
Dominant Wavelength:
- Red (619 - 624nm)
- Green (520 - 535nm)
- Blue (460 - 475nm)
Current= 20mA/Led when
- Red (2V)
- Green (3.2V)
- Blue (3.2V)

Circuit Components

3* RGB led

3* N-Mosfet transistor

9* 1kohm resistor

3* 499ohm resistor

However I would like to add 2 more LED's to my project, but I don't want to take up every single PWM. So I'm going to use n-channel transistors and duplicate per color channel pin
At 20mA per led, 3 per channel, that's only 60mA. so make sure your power supply can support that. 60 * 3, that's 180mA on the leds alone, not including the rest of the board.

schematic design for Lighting system

Then for the master board:

schematic design Aincrad master board

ERC.

Add footprint to the circuit symbols

Generate the Netlsit is the final step after finishing all the design. This step is really important in order to connect the schematic with PCBnew in which we will going to create the PCB layout. Now it's time for the layout design.

4)PCB layout

Challenge time

As soon as I start reading the Netlist I got an error message about the rgb-led Pads. at first I didn't understand it's meaning then I found the issue once I move the rgb-led away It's not connected to any other component of the circuit.
So in this section I will walk you through the steps in which I was able to solve this Challenge

Netlist reading error message

All the pads of the rgb-led is not connected.which basically the meaning of the error message.

open the footprint of the rgb-led to find that the pad name is actually a number not a letter as the message said.

However when opening the symbol library I found that the pad name is a letter. so this the cause of the problem the diffrence between the footprint and the symbol libraries.

To be able to decide which library I should modify I opened the datasheet of the rgb-led to found the pad naming is similar to the footprint library.

So modified the symbol library and change the letter to a number corresponding to it's functionallity depend on the symbol datasheet

save the Netlist one more time.

it's all looking good now.

time to continue =).

Following the same process we did in electronics design weeks and After 12 hr of routing and component placment adjustment I was able to finish all the board in 1.5 layer + RST pin.

Run ERC to make everything is good. yet I ignore it's complaining about the 2 0ohm resistors.

Route all the components, add a copper fills and silkscreen.

Final PCB in 3D.

Export .svg file from kicad for the board and Edgecut layer then run our Automatic conversion using imagemagick to get the .png files ready to be used in mods.