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BloX

The difference between 1 and 10 for adults is quite clear, though for young students this can be a difficult concept to grasp. Why does moving a 1 over and adding a 0 suddenly make ten?

BloX, which can be read about in further detail here (April’s BloX Website) is a project originally developed by April Alexander, a PhD student in Mathematics Education at Stanford University. The idea behind it is to give students a simple educational tool to help them grasp this abstract concept.

I will be helping her to make improvements to her current prototype for use in research and possible future production.

Developing The Display

The first step is to figure out how to cheaply make the small display used to indicate how many blocks have been placed in the case. April had made this work with some relatively large and expensive electronics boards, which would not be ideal for a commercial version.

Below is a video of the new BloX display spelling …BloX. It was a successful attempt to build a circuit made of cheap components capable of controlling an 8×8 dot matrix display. This could easily be used as the main display for the BloX case.

Below is a picture of the circuit itself. The three small wires coming in from the right (red, green, green) carry the signals of what to display while all of the components on the white board are used to interpret the signals and drive the display. Amazingly, the display only lights one row at a time, but it does it so fast that our eyes make it look like all the rows are working simultaneously. It is done like this to simplify the 8×8 display circuitry.

8x8 LED Matrix with Two Shift Registers

8x8 LED Matrix Display and Driving Circuitry

Clearly the above whole circuit is a little big to be used in the final BloX product, so it had to be miniaturized. Below is the how this was done. Based on the circuit used above I designed a small circuit board which could mount on the back of the LED display and use the surface mount versions (as opposed to the  through pin versions used above) of all the electronic components. I then had the board prototyped by BareBonesPCB.com and ordered the components from Digikey. The board and the surface mount components can be seen below.

Display PCB V1 With Coponents

8x8 LED Matrix Display Circuit Board and Surface Mount Components

After some tedious soldering, the whole thing mounted on the back of the LED Matrix looks like this:

8x8 LED Matrix Circuit Board

8x8 LED Matrix Display and Drive Board

The 5 pins going into the back are the 5V, 0V and 3 signal lines. It all came together pretty well, except for the LED datasheet having the pins incorrect… it was supposed to be green!

Display Board V1 Connected Front

Ha it works!

Developing the Internal Electronics

For the brains of the BloX container (what interprets how many blocks are in the container, runs the display, etc…) I’m using an 8-bit microcontroller made by Atmel, the ATMega48P.

To sense the blocks the idea is to have each block, when placed in the container, flip a small switch. Essentially the container would then count how many switches are flipped and display that. Simply this would mean 10 inputs into the microcontroller, too many! The circuit shown below simplifies this sensing from 10 digital inputs (on or off) to 1 analog input.

Block Sensing Circuit

Breadboarded Version of the Block Sensing Circuit (each dip switch represents a block)