7. Electronics design

Redraw the echo hello-world board,add (at least) a button and LED (with current-limiting resistor) check the design rules, make it, and test it extra credit: simulate its operation.

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Intro

The current week’s task was to redraw the echo hello world board utilizing Eagle and after that fabricate it. I additionally needed to add a button and a LED to the circuit.

Click HereTo Download Attiny 44 Data Sheet

These are the list of components required to design my Hello echo board

Component list:

  • 1x ATtiny44
  • 1x 10kΩ resistors
  • 1x 10uF Capacitor
  • 1x FTDI Header
  • 1x 6 pin AVRISP Header
  • 1x 20Mhz Resonator

Additional components:

  • 1x LED
  • 1x 1kΩ resistors
  • 1xPush button

My Desgining Software

Workflow

  • The first step was to design the circuit in Eagle.
  • I created a project and then created a schematic within the project.
  • I used the fab.lbr file provided to add common fab lab components to my Eagle library.

why would you want to use fab library when other libraries are available?

  • There are lots of componets are available but in fab academy we will use some exert value and designed componet will be used that collected in fab library, that make easy to student to do design an electric boardthat they will geet from one side.

How to use fab.lbr which is fab library!

  • Click on the library and open the library manager.

  • Go to Available and search the location of the Fab library Search for the fab library, there are many built-in libraries here but we are recommended to use Fab-library to make nsure availability of the Components.

  • Select it and Click Use

Fab Library is is library which is help to get the same leg’s component (SMD) which is using in our Fab Acadmey

Fab Library

  • I basically just followed the picture of the traces provided above to determine which components needed to be connected to each other.
  • To add a button to the circuit, I used the 6mm Omron switch and connected it between an unused pin on the microcontroller and ground with the pin being pulled by VCC through a 10k Ohm resistor (see schematic below).
  • This makes it so that when the button is not pressed, the pin is guaranteed to be at VCC.

  • When the button is pressed, it drops the pin to ground.

  • To add the LED, I connected it to another unused pin, a resistor, and then to ground, making sure that the cathode of the LED is towards ground.

  • This makes it so that when the pin is activated, current will flow through the LED and resistor and to ground and the LED will light up.

  • You can connect the components by directly joining both the components with nets or by giving specific name one each side of the net with Name tool. This names help us to connect the components without making it complex.

  • For ERC, It generally checks the schematic of our eclectric design. It compares Schematic with the general rules of electric circuits.

  • For DRC, SETTINGS IN CLEARANCE

    • Mil

    • Mil is dimention for traces, it is 1000th(1/1000) of Inch

    • Wire

    • It is representing the Copper wire traces

    • Pad

    • Pads on which electric components will be mounted

Via - Its through hole Diameter.

  • But knowing that the LED and resistors have the same footprint,

  • This is complete schematic of my first design, i Request not to follow this schematic if you are , I made mistake on schematic, since i had no imformation of where to put Switch i put it on reset pin and it functionality will change It will reset the board instead of controlling the LED, i will redirect you to working schematic board. click here for Working Schematic and board.

  • Rounting Sucessfully done.

Finished Schematic

  • The next step was to create the traces.
  • I created a board from the schematic by clicking the “Generate/switch to board” button.
  • Again, I followed the example board provided to plan my traces and copied it as precisely as I could.
  • I set the grid to 10 mil (to ease in finding the centers of some components) and made sure that there was always about two grids between traces (16 mil is the minimum distance for a 1/64 endmill).

Traces

  • Next I made a box around the traces and shrunk the workspace around the box, each with 40 mil clearance.
  • This allowed me to export a png with only the bottom layer visiblie in order to create the profile cut.
  • I exported one png for the profile cut and one for the traces (adjusting layer visibility each time) using the settings monochrome and 500 dpi.

Layers in Eagle

  • Layers are an essential part of Eagle. They’re allow us to organize the many types of information that are required to make a PCB, and generate the documentation that we can use in process of milling.

Common Layers for Packages

  • Each ‘layer’ in Eagle has a dedicated number, and these layers are used to separate all the types of content that make up your PCB or your parts:

  • These layers contain documentation details (layer 51), actual manufacturing info such as the ‘paste layer’ (layer 31), the copper layers for you pads (layer 1), etc.

  • Since each layer has it’s own dedicated functions, it’s important that you use the right layer for the right type of information!

  • Many tools in Eagle use layers for many different things, and thankfully they generally select the most appropriate layer by default, but for reference sake we generally the following ‘layers’ when designing packages:

    • The Smd tool (to create pads) generally uses layer 1 to indicate which side of your PCB the pad should be placed on, though in very rare circumstances you may need to use layer 16 as well:
  • Layer 1 (Top) is used to draw pads on the top of the PCB
  • Layer 16 (Bottom) is used to draw pads on the bottom of the PCB
  • On multi-layer boards with the professional version of Eagle, - you also have access to layers 2-15, but we won’t worry about these for now

  • The Line Tool can draw lines on any layer, but we’ll see shortly there are two layers that are particularly important with this tool:

    • Layer 21 (tPlace), which is used to draw lines that will be rendered as the silk screen on your PCBs (the printed text/lines/shapes we see)
    • Layer t51 (tDocu) is used for documentation purposes, such as drawing the mechanical dimensions of your part (more on that shortly!). Normally this layer isn’t printed on the PCBs, but it’s very important for documentation and for PCB design.

  • When assigning Names and Values to packages (more on that shortly as well!), the following layers are used:

    • Layer 25 (tNames) is used to hold the unique ‘names’ for each part on your PCB (ex. C1, R5, X12, etc.)
    • Layer 27 (tValues) is used to hold the value for each part (such as 10K, 0.1µF, AT86RF212, etc.)
  • We’ll cover these and other layers on an as-needed basis, and this will start to make sense once you work with them, but for now these are the main ones to familiarize yourself with.

Box for making profile

COMPONENT LIST

  1. ATtiny44 (echo hello board) - Microcontroller - Microcontroller is a small computer on a single integrated circuit. it wil take command in the sense of programmes and execute them physically with the help of various components attached to it

  2. FTDI-SMD header - For serial communications, this header are used for the Asynchronous serial communication

  3. Resonator - 20 Mhz - For Generating specific clock speed to transfer data , clock is necessary for the transmitting the data in Synchronous serial communications

  4. AVRISP header pin - To program the micro-controller, as Asynchronous communication uses the FTDI pins , for Synchronous communications this header pins are used. interface is Serial Peripheral Interface

  5. Pull out Resistor -10k - pull-outs voltage from the microcontroller for safety, these resistors will be foiund in any circuits. their function is to give the reset pin High voltage. if pin is given low voltage it will reset the microcontroller, we can do intentionally by puting swith there.

  6. Power Filtering Capacitor -1uf - Filters the power input which will go into the micro-controller , should be kept near the MCU

  • The rest of the fabrication was exactly the same as for the FabISP In-Circuit Programmer (load pictures into the fab module, send to Modela, 1/64 mill for traces, 1/32 mill for profile, clean, flux, solder, remove flux).

  • I spent a couple of hours banging my head against the wall trying to get the fab module to communicate with the Modela because apparently the module had been changed and was not left in working order.

PINS DESCRIPTION

  • Vcc - 5 volt input

  • GND - refrence voltage - consider Zero

  • Port Pins - These are the pins which can be used for the input and output. In These pins some of have special purpose. pins which can be used for the SPI interfac or Serial communication using RX and TX as i written above inn terms

  • Arduino pins - These pins Indicates arduino pin number , If one is using Arduino IDE for the programming the board These pin will be used.

  • Analog pins - All the pins of the Attiny44 can be used as the Analog input , except VCC, GND, RESET, Pin8(PWM pin).

  • Serial interface Pins - SDA and SCl pins. pins are used communication protocaol I2c. Here is link forr compare communication protocols(I2C, SPI, Asynchronous).

  • SPI interface pins - MOSI , MISO , SCK , RST Pins for serial interface

  • Timer and PWM pins - These pins can be used for the Pulse generation and oscillator applications in electric circuit. PWM is very interesting ones , which can modify the duty cycles of zero and one state. click here to understand the PWM

  • Interrupt pins - In simle way i understand this pin can Pause the programm if some interrupt is accur and start them autometically when its gone

Eagle Project - All files

Conclusion

This week seemed easy at first but it wasn’t. When the task was set the goal seemed easy because it was just redrawing a circuit and the software wasn’t very complicated except for the components part and understand the basic tools and terminologies, but there were a lot more hurdles than anticipated to cross, but by the end of the week I did feel accomplished. I didn’t know making as simple as a LED glow could be so complicated. This made me think how we have taken so much for granted all our lives. I find electronics really interesting but at certain, I got frustrated when the circuit didn’t work, not because it didn’t work but I could come up with an explanation why it didn’t.Electronics seems like a whole new universe to me and still have a lot to explore.