Sunday, April 29, 2012

LED Driver project, work in progress

I've been interested in the Arduino for a while now and played with it a little bit. Until now the most involved project I've done with it is playing around with variations on using it to program a web server with an ethernet shield. Well now I'm deep into something that is introducing me to the complexities involved in working a project up as a prototype with breadboards and then taking it to the next level by soldering components together on a generic PCB. I'm using a Philips 4794 LED driver to extend the Arduino's control of LEDs beyond the 8 or so it can control directly with pinouts. Actually I'm using 6 LED drivers to control 43 LEDs that spell out my son's name traced along his toddler version of his written name, bringing his early signature to life in a blinky way. To figure out the components and schematics I relied a lot on this post and this post, and then this post to extend to multiple LED drivers.
So, first the prototype:
 You can see here the Arduino (Duemilanove), breadboards, one LED driver, lots of leads.
And here the LEDs and the circuitry behind.

For programming I used the example in the first link above and changed the value associated with the count variable to include larger numbers of LEDs. I still don't really understand how the program works and ultimately I would like it to do something a little different than it does so I will have to figure that out later. But since that worked for 16 LEDs I started working on a more permanent version. That work in progress is below. There is a lot of soldering to do. By the time I finish, he will be in college:
All 6 LED drivers are soldered in and I tested the circuit to make sure my sloppy soldering
would work with one LED, which I was lucky enough to catch blinking for the camera.

Sloppy soldering...I will blame the cheap soldering iron until
I get a better one and will have no excuse.

Thursday, April 26, 2012

Build Your Own Computer

It's been a long time since I've written anything for no particular reason but being busy. But I recently had 20 high school girls in a class doing something I have to write about. As part of a day full of STEM activities in our high school I had a bunch of girls put together some old PC desktops we were planning to put out to pasture. It was a morning full of anticipation, exploration, frustration, and finally, pure exaltation. I provided scaffolding in the form of a Prezi they could explore  as they needed, gave them screw drivers, and pointed them towards the pile of parts. The best moments were booting up. With some false starts and reseated processors the Dell and Windows splashes started appearing on screens around the room and the girls yelled for joy. They were so excited and proud of their work.