# Electronics Design

This week is about "Electronic Design", I like such weekly tasks in which there is any electronic part. On 28th of the February, Sir Prof. Neil gave us online lecture about this week's related tasks. After His lecture I became able to clear my few queries regarding circuit production. In this week our task was to design echo hello world board.

Group Assignment

• Use the test equipment in your lab to observe the operation of a microcontroller circuit board
• Individual Assignment.

• Redraw the Echo Hello World Board.
• Add (at least) a button and LED (with current-limiting resistor).
• Checking the design rules, make it, and test it.
• Extra credit: Simulate its operation.
• Extra credit: Render it.

Digital Multimeter

"A multimeter is for electronic engineer as stethoscope is for doctor". It is most convenient and helpful equipment when we test or measure electronic components. We decided to check component in echo-hello world circuit using multimeter to confirm the values of components and to check either they are in working condition or not.

Multimeter Function description

Continuity check and Diode testing

To test the continuity and diode first turn the dial of multimeter on continuity testing function which is mentioned in above picture. Continuity test is done by checking circuit tracks with probes, if beep occurs it means that tracks are connected if there is no sound of beep or shown "1" on screen it means that tracks are not connected.

Connection testing FTDI to attiny44

Button testing, multimeter beeps when button is pressed

To check the LED we placed the black probe on cathode side (which is marked green in our LED) and red probe on anode side, if LED glows it means that it is in working condition.

LED testing

Measuring Resistance

In a echo-hello world circuit we have 3 resistors, 2 are 10k ohm and 1 is 499 ohm resistor with 1 % tolerance. To check their values we moved the dial to "20k" in resistor measuring portion and measured them.

Measuring resistance

Voltage Measurements

A circuit is powered via FTDI cable which has 6 pins in which black one is GND and red is VCC. We checked the potential difference by placing black probe on GND pin and red probe on VCC pin to check the voltage. Then we check voltage in circuit by powered it with FTDI Cable.

FTDI Cable pinouts

5V from FTDI Cable displays in Multimeter

5V is flowing in circuit

I redraw the given board of prof.Neil in eagle. As I am bit familiar with eagle software for designing the PCB boards, so it was not challenging for me to handle this week task. Here is the Neil's board:

Professor Neil's board for Echo-Hello world

I sketch the schematic of the board on a page then I followed the sketch on "schematic" part of eagle according to the specified pins.

Basic diagram of the circuit

Eagle software for PCB designing

Here, I choose Eagle CAD software for designing the PCB boards, I choose it because I worked on this software in my Final Year of my bachelors degree. In my opinion it's very easy to work with it. And, it provides well known features like printed circuit board layout, auto router, and computer aided manufacturing. I am handy with using Eagle cad software for designing of my PCBs.
Step by step process of designing the board on eagle are shown below:

Creating new file for the task in Eagle

Adding required components in schematic part of the eagle, I took all components from 'fab library'

Added all required components in schematic part of the eagle

Connected all required components in schematic part of the eagle

Board part, before routing

Design Rules:

Layers: The layers tab defines which signal layers the board actually uses, how thick the copper and isolation layers are.

Clearance: The clearance tab in eagle defines the various minimum clearance values between objects in signal layer. The actual minimum clearance between objects that belong to different signals will also be influenced by the net classes the two signals belongs too.

Size: The Sizes tab defines the minimum width of any objects in signal layers and the minimum drill diameter. The width size of objects/components which I used in this board are mostly of 2mm (~0.08in).
The minimum width of the route which i drew are 0.006 inches. It will be good if we use the route line width as 0.012 to 0.016 inches.

Distances:The Distance tab defines the minimum distance between objects in signal layers and the board dimensions, as well as that between any two drill holes. The minimum distance in traces which I used in this board are about 0.64 mm.

Checking Design Rule Check (DRC)

Size of the board in inches

Exporting image for further procedure

Setting resolution of the image as 2000 dpi, and monochrome the image

Open the exported monochrome image in paint for making another image for interior layout

Generating .rml file for interior

.rml file generated for interior (cutting the board)

Generating .rml file for traces of the board

.rml file generated for traces

Roland SRM 20 is busy in milling the board

Board is milled

Bill of materials (BoM)

Circuit board is soldered

Debugging the circuit

After soldering the board, now the next step is to check the connectivity and proper flow of the source into the board. This process is called debugging the board that is checking the connectivity of the paths and checking proper flow of source in the circuit on each component, And also mitigate the main problems which disable the board to circuit. To find out the error, we have to use digital multimeter which helps us to point out the problems, if any. So, for that I used digital multimeter, I checked connectivity of ground, VCC and other pins of microcontroller. When this step completed successfully, I jumped to the next step that is up the circuit. If this process is out of error then there is a huge chance of up the board successfully.

Now it is the time to burn boot load the circuit.

Here I burn bootloader successfully through AVR ISP circuit board. Blinking images of the circuit are shown below: