W11 Output devices

What can I do with a LED array?

Let's play with LEDs

LEDs provide visual feedback that, combined with inputs or processors, allow interaction with humans.

This week assignment was used and improved for my final project. You will find almost all data in both places.

Array LED

Charlieplexing

According to wikipedia:
Charlieplexing is a technique for driving a multiplexed display in which relatively few I/O pins on a microcontroller are used to drive an array of LEDs.  

The method uses the tri-state logic capabilities of microcontrollers in order to gain efficiency over traditional multiplexing. Although it is more efficient in its use of I/O, there are issues that cause it to be more complicated to design and render it impractical for larger displays. These issues include duty cycle, current requirements and the forward voltages of the LEDs.

Charlieplexing method help to manage many LEDs with few microcontroller pins

Summary

Modify Neil's board

Basic assignment: Starting from the Neil's LED array, add an input (I will use that PCB in my final project), debug (it doesn't work), change pin PA3 for PA5 manually (now it works).                            

Advanced assignment: Embed a slide word moving from right to left.

Content (linked):

Assignment:
LED array. Slide a word!   

LED array. Slide a word!

Starting from Array LED2 output assignment

List of needs for this PCB:
- Digital input.
- LED array

In this case, I have used Kokopelli to design the PCB. I've added a input signal.


Script will be explained on the next section.

Download c code, cad and make file here

This is my new design.

First problem (heart disease)

Wow... yes!

I want that background of led array be black, because of contrast, in other hand, I am making the final project at Fab Lab Sitges and... there is no EPOXY for the second layer.

(This PCB have 2 layers, the isulation from 2 layers is a layer of epoxy)

Well, I have no EPOXY, so I decided to try it with vinyl, so I designed and cutted the layer.

This is a nightmare!

I advise everyone to NOT use vinyl as an insulating layer. Every solder is a olimpic final. If I stay more than 1 second, vinyl start to burn, so I have to soldering "bee sting style". No way...

After finish... no all of LEDs are working

Debugging mode "on"

Let's debug all traces, leds, voltaje, ...

Microscope

Looking for some short cut, loose wire....

Soldering out

Soldering out some and come back again.

Still some LEDs are not working

Checking after any action, but still don't work.

May be is the microcontroller?

Relationship between pins and led... and...

YES!!! I GOT IT! Is pin number PA3, it's not working.

One option is to change the microcontroller, but PA5 is free now, I want to check if I change PA3 for PA5 it will work.

Let's try.

You can see a little red cable between PA5 and PA3. I put a piece of vinyl under the cable in order to avoid contact.

After that...I have to change the script, now PA5 is PA3.

Now it is working!


I want to show a message in a slide window, let's work on it.  Make all the steps that have to do the slide and script them one by one. At this video you can see a demostration.


Download the c script