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DIY LED Array Marquee For Your PC
An anonymous reader writes "Ever wish you had one of those big LED displays to keep you up to date on e-mails, stock quotes, server uptimes, or weather? Here's a new video tutorial showing how to build your own computer-controlled LED array. You can code your own data feed, and just send it over a TCP socket. This looks like a fun weekend project for someone looking to get started with electronics by building something useful."
The question is if I can do this and have it run from my car. I put in predefined phrases, and depending on which switch I hit or button, it says them?
Posts not to be taken literally. Almost everything is sarcasm.
I wrote the firmware for one of these thingies about 20 years ago. (I did it for a company that was in the electronic sign business - they made those flip-dot signs you see on buses, subways, etc.) I was lucky to have been given pretty-much complete flexibility in the firmware design, including functionality.
We used a Z-80 as the controller. The display panel was built on two identical circuit boards - they could be chained endlessly, though I don't think they ever made a wider model. It was a BIG DEAL getting the component-stuffing machine to place all those LEDs! (This wasn't surface mount, but through-holes.)
Each display panel had a shift-register - one bit per column, and just passed the bits down to the next panel. The CPU banged out bits to the shift register until the row was filled, and then enabled the row driver. Yes, we were careful to avoid refresh rates that could be a problem for epileptics.
They insisted on an asymmetrical case design - the case had a "base" that it could sit on on a desk or other surface, or it could be mounted from a ceiling. Only problem was, if it was mounted from a ceiling, it was then "upside down" and the characters had to be flipped. They were going to put a switch on the back, but I figured they would get support calls from people who wouldn't read the manual, so at my suggestion they put in a mercury switch, mounted at a 45 degree angle. The processor read the mercury switch and flipped the characters if needed.
We used an RCA flat-panel keyboard with a custom overlay. I designed icons for the various effects, and the icons were printed over letters and accessed during programming with the "ALT" key. The icons appeared on screen when in programming mode. There was a simple text-editor, and some icons accepted parameters (for example, transition effects all took an optional transition time parameter) I implemented a simple macro system [macro_name] so that text snippets could be stored and referenced from within messages. You could store multiple messages and select the one or ones to be displayed, or a timer could trigger them.
There was also a serial port through which it could be programmed. I think the idea was that it could be programmed remotely in, say, a store location. I don't know if this was ever implemented, but I vaguely recall that the idea was to send a subcarrier signal on a muzak station (that stores would already have access to) that would be decoded and passed to the serial port.
I never did install one of these in the back window of my car. I certainly entertained the thought, though. :)
I had one of the pre-production samples kicking around for years, and finally discarded it. Yea, I wish I still had that Schelbi Mark 8 too... (Mine was build on a wirewrap board - somebody was selling a kit with a wirewrap board and all the parts).
(Would be interesting to compare the designs. However, the site referenced by the article has been slashdotted...)
"Ever wish you had one of those big LED displays to keep you up to date on e-mails, stock quotes, server uptimes, or weather?
Yeah, I used to wish exactly that, but I took the easy (well, I did have to reverse-engineer the serial protocol, but that was fairly easy) way out and went to the hardware store and bought one. It's been serving my team very well since then. :-)