Content-type: text/html Set-Cookie: cookiehash=D8TIX1F9GFT8IVMEFSEXDC1UDL31CF7Q; expires=Tue, 21 Apr 2026 00:00:00 GMT; path=/; DMI News

DMI News

Previous Entry.. Next Entry..

Marquee Sign is (almost) Complete

October 21, 2010 23:34

After many many painstaking hours, the scrolling LED marquee sign is now working and functional. I have a few minor adjustments to make to complete the project, mainly mounting it to a frame and attaching a permanant power supply, but it's working. Over the next few days I'll compose a document detailing the project, both the successes and pitfalls. I'm also considering if I want to try this again, and if so, what extent I will take the next project to.

For now, anytime you send a message to the webpage it will, after any necessary moderation, display on the sign at a relatively slow pace (so it's easy to read even if the cam is updating a bit slowly). I will likely do a bit of rearranging to the back wall to make mounting the sign a bit easier, not to mention mounting it somewhere that's most likely to be visible. Other than the aforementioned issues still to address with this sign, I also need to find a font that renders decently at 8 pixels tall. The font I'm currently using only uses 7, and I might as well take advantage of that extra pixel. I'm also working on a way to submit bitmap images to have them display on the sign as well. I will also do some experimenting with the use of a timer on the circuit itself that triggers the parallel port interrupt (instead of burning cpu cycles with a for loop), as well as play with the refresh rates to see if it's possible to achieve multiple shades of gray (or in this case, green).

Future versions of the sign might include the use of multi-color, or full-color LEDs. I will also want to consider a larger array, perhaps 80x40. I will, however, refrain from doing such a project on perfboard. If it's cost effective, I will probably try to get boards pre-etched so all I need to do is solder the components on. I figure the project probably took about 5 times longer with perfboard. Pre-etched boards cost a lot though, especially in small quantities. I could etch my own easily enough, but I'd also have to drill the holes, which would signfiicantly increase the annoyance level of the project. Still, if the overall cost of the components is substantial enough, the overhead for the boards wouldn't be THAT excessive.

I figure, from the moment I started the assembly process, I spent about 20 hours working on the sign, most of that time spent soldering in the individual LEDs. Once I got a good pace going, I was managing to solder one column of 8 LEDs every 12 to 15 minutes, and there are 40 columns on the sign. As for parts, I spent $31.40 on the 6 perfboards, and about $35.00 for 1000 LEDs, of which I used 328 for this project (if the math doesn't work, I actually have one dark column. I didn't feel like using up a whole shift register just to make it light up. The chips and other accessories comes to about $10.00. Cost wise, it was cheaper to assemble it myself than to purchase a completed unit, however, that probably isn't the case once you factor in the labor cost