The Display

Below are some photographs of the final display integrated into the clothing.

The Exhibition!

Above are the 'poster' and postcards of the exhibition...

The components have arrived!

The components have arrived today! As you can see I've taken the time to organise the components. Now you just need to come and solder everything together!

Progress Report 008

Progress, PROGRESS!

As you can see from the photograph, I've now separated the transmitter (top) and receiver (bottom) circuits on two separate boards. Each circuit is running on two 9V batteries but my next task is to have it run on one 9V. Additionally the receiver is now relaying the received signal to the M32. I've used two M32's in this case just to make a quick test: the signal from the receiver circuit grounds a pin on the first M32 which in turns outputs HIGH on another pin connected to the second M32. The second M32 translates the signals into Morse code and displays it on the LCD. We won't actually be needing two M32's as the first M32 will be replaced by an inverter plus noise filter circuit in the next step.

So this is good news because the new battery-powered transmitter/receiver is now working with the old Morse code program! Of course, there's still some issues with noise, sensitivity and the need to isolate the circuit from the body: it's a matter of making it perfect now!



Transferred Message: AT YOUR SERVICE

Progress Report 007

Okay, so I have been lazy for quite some time but finally here is a post that is worth the 1 month pause!

Transmitter and Receiver are now working entirely on batteries and WITHOUT A COMMON GROUND!

I won't go into the technical details but there are still many things to perfect before this will work flawlessly. (No, we won't be using those two big racing car batteries to power the op-amp! I just ran out of 9V batteries to test) Nonetheless I think we have gotten over one of our biggest obstacles!

To convince you, Valerie, I've included a photograph and a video of the prototype. You can see that the transmitter is on the right and the receiver is on the left. There's no physical connection between the two circuits. The only contact points are the two electrodes in the middle; when a connection is made between these two points the led on the receiver will light up!

Progress Report 006

What a shame! It's been one month since the last progress report (thank goodness Valerie you've been quite busy yourself, otherwise you would have noticed my laziness and fired me)! In any case, there's some good news in this report as I've managed to re-designed the led display circuit and re-written the program. So what's the difference from the old circuit/code?

In the old circuit/code each led was connected individually to a single output pin of a shift register. The advantages were:

1) The program was very simple: shift in the data with one data line
2) 'Scrolling' effect was by default accomplished with the shift registers
3) No need to store the entire message in the M32 (the shift registers stored the data)
4) No need to receive the entire message before displaying it
5) No need to continously refresh the display

But the disadvantages became clear when I tried to make the final circuit for the shift registers: there were too many wires and shift registers! For a 10-letter display (250 led's) the circuit had 250 output wires and 32 shift registers!

So the circuit/code was re-designed today and now it functions by addressing each row of the display and having one shift register for each letter. Because there's only one shift register for each letter, the IC (we will use surface mount) can actually be physically next to the led's, so no need to stretch long wires to put the shift registers somewhere else. The advantages are clear: for a 10-letter display (250 led's) the circuit has 19 wires (10 data-lines [one for each letter], 5 wires for the rows, plus 4 wires for power/ground/clock/output-enable) and 10 shift registers! In the photo you can see the wires and the single shift regsiter (I only have one letter, but each additional letter means only adding one shift register and one wire for data). Much simpler, no?

The disadvantages are that the M32 needs to store the entire message in memory, and it also needs to continously refresh the display. It is also difficult to do the 'column-scrolling' effect, so there will instead be a 'letter-scrolling' effect (which I think is an acceptable compromise).

Please take a look at the video to see everything working! In the video I touch two electrodes, connected to two different M32's, to transfer the message. Notice that the entire message transmits quite quickly (< 1s).

Now the next step is to add at least 2 more letters to the display so I can test the letter scrolling. I will also improve the program so that it can periodically listen for new messages being sent to it. Finally I will make the display work with the morse code program. It's going to work very well!



Transferred Message: ENJOY YOUR TRIP

Order! Order!

The past two weeks were hectic, with little progress and some general disorder. But finally the desk is clean and productivity is back to normal!