TheVaporTrail

Connecting up an LED Dot Matrix Display

I connected one of the 9x11 LED dot matrix displays to a PIC16F877 microcontroller. To connect all 9 columns and 11 rows, I needed 20 i/o ports on the microcontroller. (Note that this picture is sideways and shows 11 columns and 9 rows.)

Each of the 11 rows is connected, with a resistor, to a port pin. Each of the 9 columns is connected to a transistor, and each transistor is connected to a port pin.

In the PIC code, I specified 18 bytes as the 'FRAME' memory. That is 2 bytes per column. I could have used less memory (1 1/2 bytes per column, or 14 bytes total), but I think that routines to scroll the memory will be easier when each column has its own pair of bytes.

In the 'DisplayFrame' routine I take the data for each column, write it to the ports for the column, then turn on the corresponding column bit. I call a small delay routine, then turn off the column. I do this for each column, and repeat.

Originally I planned on using a PIC16F648 with a technique called 'charlieplexing'. I now believe that charlieplexing can not be used for LED displays that are 'packaged', like all of the dot matrix displays that I know about.

More photos on Flickr

LED Dot Matrix Displays

I recently received an order of 8x8 and 9x11 LED dot matrix displays from China. I am really interested in working with dot matrix parts that have square 'dots'. I also want the dots close together. Some time ago I ordered a few 5x7 parts from Futurlec. I liked these, but wanted something bigger. None of the normal retail electronics websites carried what I was looking for. I finally found them when I started looking at the websites, such as Alibaba, that listed manufacturers.

I contacted a few different companies. I usually asked them what was their sample policy, did they have parts with "square dots", and could they provide some spec sheets. I finally settled on two companies, one for 5x7 parts and one for 8x8 parts. After many more emails, I decided to order some samples.

Now I have to come up with something to do with them.

Animated LED Pumpkin

For Halloween I thought it would be great to take one of those pumpkins you always find at the hobby store, like Michaels, and put some LEDs in it. I wanted to do more than just have them all on. I wanted them to blink in interesting patterns. I realized I could use the board I created for the FiveSquare project, which uses a PIC16F648. With this I would be able to control and animate 25 LEDs. I also realized I could add a new layout to the Animator application that matched the arrangement of LEDs on the pumpkin and be able to easily create different animations.

Read more info and downloads at TheVaporTrail

Larger photos available on Flickr

Embedding LEDs in Acrylic

I visited Synthetos this weekend to check out his workspace and laser cutter.

We had this idea to embed a classic 5mm LED into clear acrylic in a way that would showcase the shape of the LED and also let the LED illuminate an etched design in the acrylic. We started by taking a spec sheet from Lumex.com and importing it into Inkscape. Inkscape did a great with the import; all we had to do was select the LED and copy it to a new document. We cleaned up the paths so that we had just an outline. We then added the letter A to the diagram, which we converted to a path. This was what we wanted the LED to illuminate.

At the workshop, we imported this Inkscape SVG document into Corel, the environment for using the laser cutter. We cleaned it up the diagram a little and did a test cut. The first thing we found was that the LED cutout was just slightly too short for the LED we tried to put in the space. We made a quick adjustment and tried again. The LED, with the leads, fit snugly into the acrylic. When we peeled back the paper we realized that we were using frosted acrylic. This turned out to be rather fortuitous, since with the frosting we were able to see how the LED's light was spreading across the surface. It was different effect then we were looking for, but a perfect one to use.

The original idea for the etching was to convert the letter glyph to a path and to use a path effect to replace the path with a series of tiny circles. This way we could get holes all the way through the acrylic but not have to use a stencil font. The holes were too close together, and this caused the interior of the letter to fall out (exactly the reason for using a stencil font). In turns out that this was not really necessary, because we could simply adjust the power used for the letter path to get a nice deep etch without cutting through.

The end results, both with the cut-out letter on frosted acrylic and the etched letter on clear acrylic, we just what we were looking for. Our next steps are to incorporate this into a larger project. We will keep you posted.

More pictures available at TheVaporTrail on Flickr.

 

 

 

Animator: LED Animation Editor

 Animator is a small Win32 application to create and edit LED animations and sequences of animations. Animator supports multiple LED layouts, such as a 5x5 square, a 5x7 rectangle, a 8x8 square, a 8-in-a-row POV arrangement, and even a pumpkin. The application generates PIC assembly code, which can immediately be built by the Microchip IDE.

One important feature of Animator is that is stores the data for the animation in the PIC assembly comments of the same file that contains the PIC assembly. This keeps the data and the assembly together and makes it very convenient for managing the file.

The source code for the Animator application is also provided. So it is possible modify the application to write any kind of data or to generate code for PIC Basic, AVR, arduino, or any other usage.

Animator was used to create all of the animations for the FiveSquare project. In addition, there are upcoming projects that have output from Animator.

Read more, download the app, and download the sample code from Animator page of TheVaporTrail website.

FiveSquare

FiveSquare is a PIC16F628/16F648 project that uses twenty five LEDs arranged in a five-by-five square. The LEDs are mounted on a laser-cut case, which also holds the circuit board. The PIC application animates the LED display.

For more information visit TheVaporTrail

Low-Profile Benchtop Power Distribution

 I usually have many breadboard projects on my workbench. I wanted to find a convenient way to connect power to the breadboards. I had an idea to take a 40-pin connector and use it as an "outlet" with 20 sockets and making miniature "extension cords" with 2-pin headers on each end.

Read more on the web page: Benchtop Power Distribution

Iconic iPhone Picture

I learned yesterday that Safari on the iPhone will load the apple-touch-icon png file from a website if you add a bookmark to the home screen. This can either be a file at the root of the website or the file can be specified with the link tag in html.

To see a typical use, you can go to amazon or twitter, then click the "+" at the bottom of Safari and then select the "Add to Home Screen" button. This brings up a window where you can name the screen. It also shows you the icon it will use.

Sure, one icon is interesting. But then I wondered what I could do with a bunch of icons. Using Photoshop I diced up a photo into sixteen little images and saved each individually as a png file. Then I created sixteen html pages, each with the link tag referring to a different png file. I put all of these on my Mac in the Sites folder. From the iPhone I used Safari to go to each page and add it to my home screen. Once they were all saved I rearranged them on a new screen.

Not that I think anyone would really want this on their iPhone, but the first image is here. There is a 'next' link for the second image, and so on.

To help create the icons in the right place I first created a mask. If any is interested in this leave a comment and I will add it.

Sure it is useless, but who cares.

What a Great Wall!

So many steps....

I had the good fortune to be able to visit The Great Wall of China earlier this year. It was amazing. But, no matter how much you walk, there is always more.

See the big picture.

Gelato Ahead

E' Obbligatorio Il Casco Di Protezione

When I first saw this sign, from a short distance away, while wandering around Italy last summer, I thought for sure it meant that a gelato store was nearby. We were having gelato as often as we could in our travels and seeing this sign clearly indicated that more was to be had.

Clearly I don't know my Italian construction signs.