My First Feather Wing: Analog-to-Digital Converter

Hello, my fellow Makers!

Today's instructable is about something truly special. This device is MY FIRST FEATHERWING - following Adafruit's form-factor. It is also my FIRST SURFACE MOUNTED PCB! My most prominent use of this shield is in a device I made called the EMF Meter. It helps students perform hands-on experiments with moving magnets and induced EMFs.

To learn more about building the EMF Meter, please see this instructable:

DISCLAIMER: THIS CURRENT INSTRUCTABLE ONLY DISCUSSES THE SHIELD, ITSELF.

Step 1: ADS1115: the Heart of the Shield. What Is the ADS1115?

The ADS1115 is an Analog-to-Digital Converter (ADC), meaning that it reads decimal input voltages (ex. 2.489 V) and converts the measurement into bits -0s and 1s. For the ADS1115, it converts the voltage into a 16 bit reading.

This chip serves two functions:

1) to read the inputted voltage.

2) to amplify the inputted voltage (can amplify by a factor of 1, 2, 4, 6, or 2/3 before sending the digital signal).

Step 2: What Is a Featherwing?

This shield incorporates the ADS1115 circuit into a featherwing form factor, as seen in the above image.

The feathers and featherwings are a family of circuit boards that have the same shape but can serve multiple functions, such as communicating through bluetooth, sending data to the wifi, or controlling motors. This makes them easy for new comers to electronics to connect feathers together and build complex projects with little difficulty. By making an ADS1115 featherwing, I am adding it to this family of interchangeable chips.

Feathers and Featherwings were invented and popularized by Limor Fried, CEO of Adafruit Industries. To learn more about the Adafruit feathers and featherwings, look here: https://learn.adafruit.com/adafruit-feather/community-feathers-wings

Step 3: How to Connect the Shield to a Voltage Source

The feather shield can measure two voltage sources simultaneously, each voltage source being connected to one of the prongs (labeled Channel 1 and 2), as seen in image A.

To connect a single voltage source to one of these channels, take two wires that are attached to the + and - terminals of your voltage source and stick each into the female headers on the channel, as seen in image B. Make sure that the terminals are placed separately into the Channel 1/2 A and Channel 1/2 B as well. Once this connection is made, you can attach this shield to any feather of your choice to help in your experiments.

Step 4: So You Want to Make This Featherwing Part 1: Sources

If you want to make one of these chips, yourself, you are in luck, as all of the materials for this shield are available at the following sources:

THE BOARD

GitHub: Here, you can access the EAGLE .brd file, which you can personally modify to fit your project. Since the PCB requires surface mounting, the file only has solder pads in the design.

Oshpark and Seeed Studio: Oshpark publicly has my design for the ADS1115 featherwing and can deliver copies to you. If you want to order them in bulk, I would highly recommend Seeed Studio.

ELECTRICAL COMPONENTS

To order the electrical components, I use digikey, which offers a wide variety of versions of chips to choose from. The versions I used are listed here:

Ferrite Bead Inductors: https://www.digikey.com/product-detail/en/tdk-corporation/MMZ2012Y152BTD25/445-172871-1-ND/5040502

1uF Capacitors: https://www.digikey.com/product-detail/en/taiyo-yuden/LMK212B7105KG-T/587-1285-1-ND/931062

ADS1115 IC Chip: https://www.digikey.com/product-detail/en/texas-instruments/ADS1115IDGST/296-24934-1-ND/2123298

10 K Resistor Array: https://www.digikey.com/product-detail/en/panasonic-electronic-components/EXB-38V103JV/Y9103CT-ND/256604

Step 5: So You Want to Make This Featherwing Part 2: Soldering

If you are making the shield from scratch, you will need to learn how to do surface mount soldering.

I learned how to surface mount at a place called Next Fab. They offer many lessons and one-on-one tutoring.

If you have the equipment to surface mount solder at home, then feel free to solder in the comforts of your personal makerspace. Otherwise, with membership, you can also do your soldering in Next Fab Lab. Currently, that is where all of my soldering takes place.

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