Business Card Exchanger

Impress your potential employers by adding a theatrical element to the business card exchange.


This project takes you through the steps of how to create a box that will light up and open when it hears a specific knock.


There is an internal button that will allow you to reprogram the knock.


Here is a video to support the design:



Important Notes:

  • This box does not guaranteed job placement. It only attempts to create a way to leave a lasting impression through the business card exchange.


Step 1: Tools, Supplies, and Skills



Based on your level of experience this project could take several hours to complete.



To complete this project you should have a working knowledge of:

  • Soldering
  • Reading a wiring schematic
  • Working with Arduino and code
  • Working with Rhino



  • Solding iron and solder
  • Heat shrink
  • Wire stripper
  • Safety glasses



  • 1 Arduino
  • 1 stepper motor and motor drive
  • Leds
  • Wire
  • 1 Piezo speaker
  • 1 red led
  • 1 green led
  • 1 Transistor 2222
  • 1 2.2k ohm resistor
  • 1 10k ohm resistor
  • 1 1M ohm resistor
  • 1 small piece of perf board
  • 1 9 volt battery clip and 9v battery



This case was 3d printed, but you can make a box out of any material. I have outlined the steps of how to do the 3d modeling in step KP and also include the .stl file below. You can use the .stl file to directly output to a 3d printer. If you do not have access to a printer you can have it out sourced to companies like Shapeways.


Step 2: Program the Arduino


First, you should open up the Arduino program and attach your microcontroller to your computer. We are uploading the sketch first so that we can test the electronics during each step up the wiring set up.


#1: Download the sketch

Download the file xxxxx.pde at the bottom of this section, copy it to your sketchbook and upload to your Arduino.


Code overview:


Step 3: Lay Out and Test the Circuit


This step will outline how to breadboard the electronics. I have provided a schematic to diagram the breadboard. Since the code is already uploaded to the Arduino, you can test each element as you go to see if you did it correctly.


#1 Wire the Piezo Sensor

Connect the Piezo speaker between Analog pin 0 and the ground. Make sure to interrupt the connection with a 1M ohm resistor.


#2 Wire the LEDs

Connect the red LED to digital pin 4 and the green LED to digital pin 5. Make sure to put a 560 ohm resister in line with each of the LEDs.


#3 Wire the programming button

Attach the button to your breadboard and connect one side to 5v. The other side should be connected to digital pin 2 with a 10K resistor inline to the ground.


#4 Wire the stepper motor


Step 4: Model the Case

Next I will take you through the steps outlining how to model the case. If you do not want to use my box design, I have also attached a drawing that illustrates how the case functions so that you can apply the mechanics to another material. I have also attached the .stl file so that you can print the box yourself.


Step 5: Assemble

Now that your circuit is assembled and box printed, all you have left to do is put it all together.




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