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7. Electronics Design

Here is the echoHelloWorld board I made riffing off of Neil’s board. The different being it is much bigger and has a button, current limiting resistor and LED.


Eagle: Schematic | Board

Testing w/ Oscilloscope

I’ve never used an oscilloscope before. After a quick search I found a video that has a really great tutorial. I tested an arduino with a PWM LED that changed the brightness of the LED by varing the pulse time. The video below shows the time between pulses for each brightness.

Schematic in Eagle

When Eagle starts up I clicked to start a NEW SCHEMATIC. The blank schematic opened and I started adding/loading my favorite part libraries.

The Fab Academy library is a must and that Adafruit library has a bunch of parts that I also like to use.

After clicking EDIT/ADD I searched for all the parts on the circuit board.Once OK is clicked the part symbol can be moved around on the screen and rotated by right clicking.

Although the symbols don’t snap together it is easy to make basic connections and reselect the parts by clicking on the + at the center of each part.

The NET button on the bottom left of the toolbar allows you to make connections between parts. I think of it like adding wires or cicuit board traces.

Board Layout in Eagle

With all the parts arranged and connected on the schematic view I toggle over to the board layout view.

The board starts as a default size and all the parts are located in a pile off the board connected by yellow lines. These yellow lines reflect the connections made by the nets on the schematic view.

I learned with the previous board I designed that autotrace doesn’t work well for one sided boards. For this board I made all the wire paths manually by clicking the ROUTE button. There are several places to define the wire width. My favorite place to make this change it at the top menu bar when then ROUTE tool is selected. The width can be changed via a drop down menu.

.4064 works well for my mill and boards.

The width of each wire can be individually assigned by right clicking on the trace and clicking properties.

I noticed after milling the board that some of the wires are two close to the pads and were difficult to mill. As you can see in this image the wires snap to the GRID.

I was able to half the grid size and move the wire over, centered between the pads.

After the board was arranged in eagle I exported the gerber filed using Eagle’s CAMprocessor.

Milling Board

The board was fabricated using the same process as Week 5 using CopperCAM.

Here you can see the trace that was placed too close to the pad. With the board layout change made above I was able to re-mill the board and solve the problem. Luckily I noticed this issue before I soldered the board and plugged it in.

Stuffing Board

I gathered all the parts for the board.

Parts for Echo Hello World Board

  • Atmel Tiny44
  • 6 Pin FTDI Connector
  • ICSP Connector
  • 20 MHz Oscillator
  • 10K Ohm Resistor
  • 1uF Capacitor
  • 330 Ohm Resistor
  • LED
  • Button

Each part was anchored to the board with a single wolder point. This allowed me to shift the component by melting the solder. Then, I soldered all the other connection points.

The board came out really clean.