2.1 | Circuit Design

Before actually drawing the circuit, first we need to understand the properties and functions of all the blocks.

​The properties of different function blocks：

• ​Start-Block
  - Send signal to trigger all the other blocks connected after it

• Syllable-Block ​​​
  - able to receive signal from previous block
  - emit a sound when it is triggered
  - emit a sound when the button is pressed
  - change of sound duration with a potentiometer
  - able to pass the signal and trigger the next connected block

• Pause-Block ​​​
  - able to receive signal from previous block
  - able to hold the signal for a certain time before passing it to the next block
  - able to pass the signal and trigger the next connected block

• Switch-Block
  - able to receive and pass the signal to either one of it output with a toggle switch

• Loop-Block
  - able to receive signal from previous
  - able to execute the block sequence within the loop for several time before passing the signal to next block 

2.1.1 Designing

Autodesk Tinkercad Circuit have been used in designing and testing the circuit.

​Autodesk Tinkercad Circuit is an online circuit development and simulation tool. It allow users to upload their own code and simulate the Arduino board.

Fig. 1. Designing a "Syllable-Block" circuit(top) and a "Start-Block" circuit(bottom) using Tinkercad

2.1.2 Prototyping and Testing

The designed circuit were then build with an actual Arduino board. The code were also uploaded to it for testing and debugging. In the design, each blocks will be connected with three pins: two signal pins and one ground(GND) pin.

Fig. 2. A functional "Syllable-Block" circuit

Several more circuit prototype have been made for testing the connection between two or more blocks.

Fig. 3. Two functional "Syllable-Block" circuits being connected

2.1.3 Finalized Circuit Design

After going through designing, testing and debugging process, the circuit for all the blocks were finalized.

(Click below to view large image)

"Start-Block" Circuit

"Syllable-Block" Circuit

"Pause-Block" Circuit

"Loop-Block"(Begin) Circuit

"Loop-Block"(End) Circuit

"Switch-Block" Circuit

2.1.4 Circuit Shrinkage 

The circuit prototype above is too large to be an actual playable building block for children. The size of the Arduino board and the breadboard are too big, and the circuit need to be self-contained without any USB wire connecting to computer. As this toolkit is targeting to children and younger age, their hand size also needed to be consider. It seems to be an acceptable size that each building block should be smaller or equal to the size of a standard Rubik's cube. 

Fig. 4. components used in the circuit

• Breadboard
  The full-size breadboard (165.1 x 54.29 x 9.68mm)
  will be replaced by a mini breadboard (46 x 36 x 9.68mm)
• Arduino Board
  ​The Arduino Uno board (68.6 x 53.4 mm)
  will be replaced by a Arduino Mini Pro (17.78 x 33.02mm)
• Power Source
  ​The USB cable 
  will be replaced by a 3.7v battery with
  ​a boost converter convert it to a stable 5v output.

With the above components, the circuit were rebuild and the size has been decrease for around 50%.  

Fig. 5. Original circuit prototype(top), and resized circuit(bottom)

2.1.5 Connection

Since this toolkit is designed for BVI students, every building blocks have to be easily connected without the help of vision. Therefore, I came up with an idea of using magnet and conductive tapes to build the connection. By doing so, the blocks can be easily snap with each other and the signal can also be transmitted.

Fig. 6. Cooper tape(left), conductive fiber tape(right)

Conductive Tape Testing
Connection and signal transmission is very important in this toolkit. There are two main types of conductive tape in the market: copper tape and conductive fiber tape. A test have been conducted to find out the best conductive tape for this project. ​​ Two wooden cubes and a simple circuit have been made to simulate two building blocks. The two end of the circuit will be connected to each of the box using conductive tape. The two building boxes will then put together to see if the current could able to transmit from one end to other end. If the circuit is completed, a LED will lights up.

Fig. 7. Two wooden boxes and with a simple circuit have been made for testing different conductive tape

Test Result

The result suggested that conductive fiber could be a better choice in connecting the circuit between two building blocks. 

Fig. 8. Test result for copper tape(left) and conductive fiber tape(right)