Homemade Hardware

Steps to Making a PCB

Design

  1. Prototype

  2. Bill of Materials

  3. Schematic

  4. Layout & Shape

  5. Design Copper

Production

  1. Cutout & Holes

  2. Remove Copper

  3. Board Finishing

  4. Populate & Reflow

  5. Programming

Physical Computing

Design #1

The Physical Computing website is packed with everything you'll need to know about electronics and programming for this class. Specifically, the following pages should be reviewed:

Topics

Labs

Microcontrollers

Design #2

We'll be sticking with Arduino-compatible chipsets in this class so we don't have to leave the Arduino IDE. However, when making your own boards, it helps to have a grasp of what's happenning at lower levels.

Under the hood

Arduino Board Manager

Bootload and Code on the ATtiny

  1. Turn your Uno into an In-System-Programmer (ISP) that can flash other AVR microcontrollers.

    • Select Arduino Uno in the IDE

    • upload the example sketch "File/Examples/ArduinoISP".

    • Go to the menu Tools->Programmer: and select Arduino as ISP (do NOT select "ArduinoISP", that is totally different).

  2. Select "ATtiny25/45/85" from Tools->Board

    • You need "ATTinyCore" installed, see link above to install if you don't see it in your menu

  3. Check that the settings are correct:

    • processor = ATtiny85
    • clock = internal 1mhz
      • ... or 8mhz or 16mhz are OK. Just make sure it's the same when both "flashing the bootloader" and uploading your code later on.

  4. Wire your ATtiny85's SPI and RESET pins to the Arduino Uno's SPI and D10 pins:

  5. Flash the bootloader! This will set the ATtiny85 to the clock speed you selected. Go to Tools->Burn Bootloader (make sure ATtiny85 is the target board, and you have "Arduino as ISP" as your programmer). If you get an ERROR, either:

    1. you're not powering the ATtiny85 correctly
    2. you have incorrect wiring or a broken cable
    3. you don't have "Tools/Programmer/Arduino as ISP" selected as your programmer (not "ArduinoISP")
    4. you don't have the "File/Examples/ArduinoISP" sketch uploaded to your Arduino Uno
    5. you don't have the ATtiny85 selected as your target board
    6. you accidentally broke you ATtiny85 or the Arduino Uno. Try another, and if it still errors, see reasons above.

  6. Make something :) Here is a link to ATtiny85 pin description (Arduino pins are labelled blue in the picture), and also other hardware descriptions for connecting to different sensors and outputs.

[FYI] ATmega328p on a Breadboard

Eagle Schematic

Design #3

Here's a thorough list of Eagle Commands from MIT's course on Eagle.

Adding Parts

The Adafruit Eagle library and the Sparkfun Eagle libraries have a ton of parts for you to use.

Here is a very helpful search tool created by Dangerous Prototypes. You enter a part number you need, and it searches GitHub for any Eagle files that contain that part, so you can simply copy/paste into your design.

Making a Schematic

Sparkfun tutorial on Eagle's schematic view.

Video from Class #2:

Eagle Board View

Design #4

A simple list of the Eagle commands, for quick reference.

Turning a Schematic in to a Board View

Sparkfun tutorial on Eagle's board view, stop when you get to "Routing the Board".

Eagle Routing

Design #5

A simple list of the Eagle commands, for quick reference.

Drawing Routes

Start at "Routing the Board" in the Sparkfun tutorial on Eagle's board view, stop when you get to "Generating Gerbers".

Using the OtherMill

Production #1

1 - Load design and bits

Drag and drop your Eagle .brd file into Otherplan, and your design will appear in 3d model and as a new entry on the right side. Add all the bits you will be using for this board (aka 1/32", 1/16")

2 - Inspect and adjust Eagle file

With the correct bits selected, carefully look over your design and check to see if any traces are too close, or any holes are too small they won't be drilled. (link to Bantam Tool's Design Considerations)

To fix any problems, keep Otherplan open, and also open the Eagle file to edit. Adjust your traces, or drop new holes, and press SAVE in Eagle. You can then press the refresh key on your file in Otherplan, and the changes will appear.

3 - Connect to Othermill

Once your file is ready to be milled, you can start using the machine.

Power the Othermill on, and connect to your laptop over the USB cable. Otherplan should now say that you are connected to a mill, and can control it.

4 - Optional: Attach Bracket and Locate

This is only needed if you are doing a double-sided PCB. Read Bantam Tool's guide for how to probe the bracket.

5 - Prepare copper plate

The Othermill is designed to hold plates 5"x4". If your board is larger than this, you can cut it to size in the shop.

Apply double-sided tape to the bottom of your board, and press if firmly down onto the Othermill's bed. Press firmly and for about 30 seconds, making sure that the tape fully stuck and flat to the aluminum bed.

6 - Change Tool and Locate

The top-right of Otherplan will show what bit it thinks is currently connected. This might not be a bit your using, or could just be completely wrong, the machine's not that smart.

Select Change Tool, and follow the instructions. You should add the smallest bit your job is using (aka 1/32"), and follow the instructions for locating. The bits must be located every time after they're inserted.

7 - [New Feature] PCB Probe

This is great. If you have the PCB Probing System, then the machine can measure the thickness of your board for you. Read Bantam's guide for how to use it.

Simply though, with the PCB probe touching your copper plate, go to Menu_Bar->BitBreaker->Probe_Material_Thickess.

If your bit doesn't cut through the copper while cutting, it means some spots on your plate are thinner than others. When this happens, cancel your job, and got up to the Material box in the software and open the Size section. Lower the thickness by 0.05-0.1mm, so if mine was 1.52mm before, I'll change it to 1.50 or even 1.47. Press ENTER so the value is saved, then try milling again.

8 - Run Job

Once correct bit is setup, and your material is ok, you can press "Start Cutting!". While the job is running, do not listen to headphones, and do not leave the machine alone.

If your job is using multiple bits, the machine will automatically stop and ask you to change bits. Follow the instructions just like before, and it will continue with the job.

9 - Remove and clean

Once the job is finished, use a vacuum to clean both your board and the entire insides of the Othermill (including those hard-to-reach places in the top).

Scrub your board with a scour pad to remove any roughness and copper hairs, and test all connections with a multimeter

Engraving Bit Isolation Milling

Production #2

Bantam Tool's has the feature of using an 30 degreen engraving bit to millout the a circuits traces. This is an amazing new feature that allows us to mill much much smaller traces and component pads.

Here's a link to their tutorial on using the new feature.

Cleaning a Milled Copper Plate

Production #3

[WARNING] The below video is old, and we now can mill double sided boards on the same plate. However, the same rules apply when cleaning it.

Tutorials on Soldering

Production #4

[WARNING] The below videos are old, and we now can mill double sided boards on the same plate. However, the same rules apply when soldering.

Sparkfun's Tutorials on SMD Soldering


Sparkfun's tutorials
are focused on how to solder the parts down, whether using an iron, hot air gun, skillet, or toaster oven.

Programming Jigs

Production #5

  • Here's a tutorial on making a "real" programming jig. This is too professional for what we'll be doing in class, but you can imagine how much design goes into just thinking about how something will be programmed.
  • Here's an example of someone hot-gluing some wire to program a dead Pro Mini. That's a jig too.

Bootloaders

Production #5

A Bootloader is a small piece of code that we usually need to put on our microcontrollers before we can program them with Arduino. Any board that works with the Arduino IDE has an "Arduino" bootloader inside it, giving it the ability to load code from the Arduino IDE.

Here's an explanation of what the Arduino Bootloader is from Sparkfun.

Whenever code is transfered from a computer to a microcontroller, something must be in the middle acting as a converter. This is a usb-to-serial converter, or a usb-to-spi converter, or something similar. These middle devices are call In-System Programmers (ISP).

Here's a tutorial on using Arduino as an ISP (In System Programmer)

Here's an example of adding a bootloader to an nRF51822, so that we can program it with Arduino. Unlike Atmel chips which use the mkii as an ISP, the nRF5x chips use the J-Link as an ISP.

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