FabAcademy Final Project

FabAcademy Final Project

The project is a shelf that knows when a tool is missing. It should send a message to a webpage that shows which tools are missing.

The Skills
Planning. Designing.
I modeled my design using Fusion 360 and Sketchup for artistic work.
I used Pixlr for Raster Graphics
I used CorelDraw and Inkscape for Vector graphics.
Project Management
I wanted to focus on a single shelf especially the electronics and interfacing those electronics with the computer. Hopefully in future, I can expand functionality and scale.
LaserCut Pieces class=
CNC Laser Cutting
I used the laser cutter to cut a mockup wood shelf that I was going to use for testing. However, the mockup, looked better than the composite shelf. So I just started using the wood shelf.
I laser cut a case for one of the PCB boards.
I laser cut burlap pieces for building the shelf(which I did not like.)

Milled Boards
Electronic Production
I designed a board using a raster graphic program.
I planned out future boards for LEDs and RFID using Eagle.
The board is made using a Carvey
Embedded Programming
I programmed Attiny45 to read capacitance and relay the signal to a second board(Arduino Uno/Arduino Mega). That board is connected to a computer via FTDI cable.
Input Devices
I have built the TX/RX step response example and modified the board for my use.

I have a simple serial connection between the sensors and an additional microcontroller that is connected to a computer.
I designed my own app. It used Node.js to communicate with the microcontroller. It used javascript to display the info.
In my second iteration, I adapted the python program that came with the RXTX application.
The Process
I had three major areas to work on. To keep the project moving, I worked on these three areas in parallel.
Machining, Milling, & Molding


  • Construct a shelf to hold tools.
  • Construct a mount for electronics.
  • Construct a frame to hold shelf and accessories(CNC mill.)
  • Plan

    The shelf is constructed out of burlap/resin composite. The technique is wet layup with compression. In order to make the tool trays, I am modling the composite around a XPS foam mold. The mold is made using the CNC Mill(Carvey).
  • Design the mold using Autodesk Fusion
  • Generate the GCode using FAbModules.
  • Cut the Molds using CNC Mill(Carvey).
  • Soak the Burlap in the Resin(SuperSap One)
  • Clamp the two molds(male and female molds) to press two layers of composite together.
  • Demold the individual pieces. Combine pieces to make top of shelf.
  • Coat the shelf with gel coat.

  • I ended up modelling the original plans in Fusion 360. I did not need a 3d structure since I was going to make molds using the CNC mill and laser cutter. I modelled a wood structure that originally was going to be a mockup using CorelDraw. I used Easel to model the pieces(3) for the CNC mill.

    Casting and Molding

    Each indentation of the shelf holds a tray. The tray is made by casting the outline of a tool so that each tool has a specific location.
    To make the trays, a photograph of the tool was taken. The outline of the tool was made using the spline tool in CorelDraw. The image was saved in a SVG. The SVG was used to generate the gCode using Easel(However, this could be done with FabModules as well.)

    I chose to use SmoothCast 326 because it was labled as semi-rigid. I still find it to be sticky and its apperance glossier than I imagined.
    I decided I like the styrofoam molds better. I milled both postive and negtive molds for the tools.
    Instead of pouring money into finding a better casting plastic, I want to laser cut tool foam some time in the future.

    After taking the time to build molds for casting and composite building, I prefered wood and foam. Originally, I built the wood and foam to do testing while I made molds and prepped the structure.
    Here is the "final" structure:
    Electronics(Circuitry & Programming)


  • The electronics need to identify if a tool is present.
  • Ideally, a system of electronics can identify the area in which the tool can be located.
  • The signal/status needs to be sent to a central hub.
  • Plan

  • Build a capacitive sensor that goes under the tool holder.
  • Program the capacitor sensor board to read capacitance, determine whether or not the value has changed from a baseline value. Update the status to a central microcontroller.
  • Get the sensor to send info to a 2nd microcontroller(hub)
  • Get the second microcontroller to relay each sensors info to web app.
  • Stretch goals:
      Build a rfid system(transmitter on each tool and reader at tool hub.
      Add some led indicators.
  • Process

    Building the capacitive sensor....
    I want the sensors to lay under the tools. This means I want to build the board without any header pins. This worked out, but in hindsight, I would design my circuit with header pins and de-solder the header pins after programming.

    The sensor was hand drawn using Pixlr. The image was then shrunk so that the chip size matched the Attiny45.

    Soldering A 1M resistor was soldered between RX and Ground and RX and VCC. A 1uF capacitor was soldered between VCC and Ground. A jumper wire was wired to the back side of the Double PCB from the TX. In order to program the board, I soldered wires onto each of the programming Pins. At this point, the location of the pins is easy by memory, but for reference:
    Pin 1 --> RST
    Pin 2--> Not needed for programming
    Pin 3 --> Not needed for programming
    Pin 4 --> Ground
    Pin 5 --> MOSI
    Pin 6 --> MISO
    Pin 7 --> SCK
    Pin 8 --> VCC

    Arduino has an example to program the sensor:
    I used the Capacitance Sensor Example sketch with only modification of the pins.
    I used pins PB3 and PB4 as RX/TX.
                        CapacitiveSensor   cs_4_2 = CapacitiveSensor(4,2);
                         CapacitiveSensor   cs_4_3 = CapacitiveSensor(4,3);
    Only one sensor is needed because I choose to use microcontrollers on each sensor as opposed to one Attiny45 for 3 sensors.

                        CapacitiveSensor   cs_4_3 = CapacitiveSensor(4,3);
                        void setup(){
                        void loop(){
                            long total1 =  cs_4_e.capacitiveSensor(30);
    The example gives a nice readout. However, there is a lag in the time, in which a tool is moved.


    After presenting my project(Jun 20), Neil suggested using the Capacitance Sensor in his example. This would solve two of my problems. I needed to ground my tools(physical contact) and I needed to acquire samples over about 10 seconds to account for noise.
    My board was the same. Not suprising since I had looked at Neil's example and the example on the Arduino site before building my sensor.
    The only thing that need to be done was a change in code.
    I am still struggle with understanding Neil's Example Code. I will work on that. There are many references to the board that I have not learned and am struggling to grasp. However, the functionality of the code was the same, and my pins are the same as well.
    I just have to pay attention to his ouput.(more on this in interfacing)
    Interface Building


  • Receive Serial Communication(Tool Status Updates) from microcontrollers to a computer.
  • Create a Node Server/Web Socket to display data on a webpage
  • Display missing tools.
  • Stretch Goals

  • Recieve RFID info from each hub to a computer
  • Identify and display the area in which a tagged tool can be found.
  • Add bluetooth or radio so that the computer can be located away from the tool hub.
  • Process

    I investigated several ways to implement this process(Getting the microcontroller(s) to talk to a web client.) I have node.js and websocket installed from previous work and examples.
    I choose to use Firmata, because I can program through the Arduino IDE.

    Firmata is a protocol for a microcontroller to talk to a computer. This will allow me to write a custom webpage that is getting info from the microcontroller.

    Update: many hours were wasted on that one point. I did not realize that most of the time when I npm install, it provides only local. That is easy to see from the placement of the folder node_modules, but at the time ......These packages need to be installed in each project or globally.
    To understand how to use Firmata, I found this tutorial helpful: OpenChapters.

    The example found in the Arduino IDE: StandardFirmata can be uploaded to the board.
    This gives a webpage access to the input and outputs of the board.
    You can use many different applications to talk to the microcontroller, but I want to focus on javascript/HTML5.

    Here are the Client Libraries that can be used to find examples.

    This allows us to receive the Analog Data from the microcontroller.
    That signal can be processed to determine whether or not a tool is in its holder.
    A display can be developed to show the status of all tools.

    In my first iteration of the project, I stuggled with websocket. To get around this, I had node.js save the data from the microcontroller:
    Javascript File
    Here is the HTML5/JS WebApp:
    Tool Sleuth

    The app worked fine. But.... It was not elegant enough for me.

    After the presentation of my project, Neil suggested looking at his sensor. When I did this, I also adapted his code to write a python based interface. It is an OK stop gap to getting the project working.
    I used the python code from Neil's RX/TX: Python Code found in the week on Input Devices.
    Here is the readout when all tools are available:
    After removing a tool:
    Python Adaptation/Neil's Code