Electronics design (Feb 27)

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Assignment
    Redraw the echo hello-world board, add (at least) a button and LED (with current-limiting resistor), check the design rules, and make it

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For design of the PCB, I used the Eagle software. This is a simple software and easy to learn. To install it,Choose "Run as Freeware" on first run.

• Eagle Library

Luciano sent us a Fablab library for Eagle, but the FTDI connectors I did not found. I found them in the SparkFun eagle library , specifically Sparkfun-Connectors.lbr

I added the FTDI connector to the Fab Hello.lbr and I changed the name to Fab RHello.lbr . To install, copy these files in your folder \Eagle\lbr

• Tutorials

http://www.cadsoftusa.com/download-eagle/

• Schematic note
  

1. Use the Fab RHello.lbr to add the components
2. Connect components with Net don't Wire
3. Microcontrollers note: 
   
1. You use a decoupling capacitor between VCC and GND near of the microcontroller, in general 100nF.
   
2. The micontroler IO ports usually are able to absorb more current than it can be supplied. Connect the LEDs to VCC instead of to GND and turn on by 0. LEDs have polarity be careful.
   
3. When reading a microcontroler port, make sure the cable is not in the air, you can use pull-up or pulldown resistors to force states reading.Some microcontrollers have them internally and are configurable

4. When you finish the schematic, click in Board to generate the PCB with this schematic.
5. If you have crossing tracks, you can use resistors 0 ohm as a bridge.
6. You can generate new components after, remember click in Board to refresh it.
   

• PCB note
  

1. The correct position of the components makes easier our job later. Check the correct position to minimize the distance between pins.
2. Then use the icon Route  to create tracks.Use 45 degrees to route, never 90. Electrons move along a track like water through a pipe.
3. You can undo a track routed by pressing RipUp.
   
4. Configure Eagle for black background. This is useful for creating the PNG image to the Modela. "Options -> User Interface" Layout/Bacground select black
5. To generate the ground plane use a polygon never a rectangle. Select these icons with 0.016 Isolate and 0.016 spacing
   

6. To create the PNG image, you select Display icon first, and choose None and after only Top. Then go to File -> Expot -> Image ( select Monocrome and 500dpi )
   

  Files of R hello world board

r hello world board.sch
r hello world board.brd
r hello world board.png
cut r hello world board.png

Schematic	PCB
Cut png	PCB png
PCB fabrication