| ??? 11/09/09 13:05 Read: times |
#170582 - Wait a minute ... Responding to: ???'s previous message |
Per Westermark said:
A good way to get even light is to have a constant LED density for all words. One simple way to do that is to use one LED/character. So a eleven-character word lights 11 LED. This would also make it simpler with diffuers.
Next thing - what does it matter if you can do it in 1kB? The majority if 8051 chips have 4kB or more. It doesn't, except that writing, checking, debugging, correcting, etc, 1 kB of code is a bit less effort than 4kB. Of course, if it's written in 'C', the first kB will just be library overhead. But 11x10 characters seen as 11x10 pixels is 110 bits or 13.75 bytes. 12 hours*14 bytes + 12 minute states*14 bytes is 336 bytes. So it should be possible to do it in less than 1kB with a LED/character too. Adding a couple of extra lines of code, the lookup table can be shrunk even more. Where do the pixels come from? The characters are permanently etched/engraved in the mask, hence pixels aren't really relevant at all. You're suggesting one LED for per character. A character isn't a 2.5 mm LED's size, but, rather, has to be visible and readable from across the room, if you're doing what the original project example shows. Surely you don't intend to make the characters that small. OTOH, if you want to use multiple LED's per character, it becomes a larger array, doesn't it? Using multiplexing or not really isn't a problem. I didn't say it was a problem, though I did say I believe there's no need for it at all. There's no need to compute the value of pi or to run an FFT, either. Tiny code and trivially small. The processor is hardly likely to need the power for something else, so it is irrelevant if it refreshes the display or if you have a statically driven display. And the power for driving the LEDs will make it irrelevant if a multiplexed display makes the CPU process some extra instructions. Just because you would not like to solve the problem with a LED matrix is no reason to consider it a non-applicable solution. It really is a well working solution. And guess what? You would not have to rewire any PCB and rearrange any LEDs depending on language. So you think a student project should include other languages, too? From earlier discussions, you would know how easy you can dim down the intensity during the night. With each series resistor only controlling a single LED at a time, you would not need to find different resistance values depending on the LED count for a word.
Making use of one extra signal and buying dual-LED modules would allow red or green selectable. Two signals would allow red, green or yellow. Where did a requirement for multiple colors originate? Do you believe that a project, whether from a school project or a commercial development, should include features not specifically included in the project requirements? How would you do that with those 2cm x 2cm 8x8 LED matrices, and why? I'm not disagreeing with the comments you've made about any of this, aside from the fact I'm curious how you'd apply those 8x8 LED matrices, of which Erik seems to believe you'd need only three. While I believe there's some confusion about device type and method of application, I doubt you're on the same page with him, and I don't understand how you'd do this. While I'm sure it's "doable" I don't think any single description provided so far has covered it. I'll bet I'm not alone in this. COuld you provide a description of exactly what you mean? ... one that's not mixing the word-elements with pixels and other features not yet justified? As I said, I'm willing to believe it can be done with the features you've suggested, but, since the words are not subdivided into characters that are applied outside those specific words, I don't see how pixels, multiple LED's and the like are to be used. Please clarify this by providing a complete and precise description of your approach. You needn't include any code or even description of it, but I believe, in order to understand what you suggest, we'll need to know where you intend to put the LED's, how many there will be, why you need that number, how large your display is, and other details such as that. RE |
