Wall of RAM

Well, in the excitement I forgot that 4,096 bytes is 32,768 bits. A little out of my range.

So maybe we settle on 1k of ram. I don't think I have 32,000 leds of wall space to spare!!! ;)

On second thought, a 1k ram wall would be 121x121" square. I just got done drafting it. I think maybe I should consider one 256 byte array and see how it goes.

What considerations will I have to make for wire length? Possibly use a differential transciever set?

All right, I'm not crazy any more. If I even try this I'll just use some dual port sram and fake it. That should be easier and allow a switch to choose which 1k bank of the memory to look at. A little more flexible. ;)

when you said 4K I thought you meant bits. and that it sounded possible but lots of work.

reduce the clock speed until it starts working?

Bye. Jasen

I don't know. These aren't very bright LEDs.

Here is what 1kbyte would look like:

and a 1 to 1 scale:

You may think its crazy...but what am I supposed to do with my 50,000 LEDs???

How many lights/led's would that be? Calculating your original thoughts showed scary amperage and blinding candle-power. I could be wrong, just a thought. Bart

Up here in Alaska we don't have much desert sun, so that might be a problem. ;)

Here is a picture of a 26x22 array. I got this far and then was worn out. Used a little over 500 LEDs on this one! I was worn out because the board was wired completely by hand. I would use a PCB from a company on this project...

Put all of them in an array (~220 * 220) ,wire them in groups serial an parallel, and in desert sun you have a nice solar panel.(I do not know what the output would be) -)-)-)

Just a thought, if you're going thru so much labor, maybe have a board drilled to make a significant sign, shape, or lettering that you could sell to a business or school, donate to a church. Bart

I've been looking for some for a similar type of project. My idea was to have a computer case that displays certain patterns, graphics effects such as: plasma

Fire Conway's Game of Life (Haven't posted the applet for that one yet)

I might be interested in buying a few thousand LEDs from you :-) Depending on their specs.

Say, do you have a range of colors? I'm probably stupid to ask for it, but a couple hundred LEDs could be nice for a whacky project. Probably is stupid since about the only indicator I use regularly is my oscilloscope...

Ooo, nice.

Not that I know of. LEDs are exponential, not negative-resistance, like neon lights are. If you had gotten a couple ten-thousand neon lights, you could do it (although clock would have to be slowed to the 10kHz range!).

You'll need at least 8,192 transistors and 16,384 resistors, to make yea many RTL inverter R-S flip-flops. To burn LEDs, I suggest using a red to indicate OFF and a green to indicate ON for each bit. A negative or positive pulse to the base (supplied by resistor or capacitor) sets state, while electrical state is read by collector voltage. RTL with typical transistors will switch in a 100-200 nanoseconds, so should be able to keep up with a standard clock. I'm not sure how you're going to address it, since you need essentially eight 9 to 512 decoders!

Lesse, at 5mA per LED, that's a good 25 amperes supply current. 'Gonna want that as low as possible, i.e., 5V or so. Total dissipation will be on the order of 125W, not too bad.

For the wiring, runs several feet long will want to be coax or at least laid against a ground plane or something. Terminating resistors might be a good idea.

Tim

-- Deep Fryer: a very philosophical monk. Website:

...

Yes, but it'd be a nightmare to design; you'd have to come up with a whole refresh scheme. I'd use flip-flops or real RAM.

I think you're crazy, but it does sound like a kewl idea. :-)

If you want to do it, (and have the cash) do it. "If you build it, they will come". :-) Take pictures, and _then_ see what other people think. :-)

Good Luck! Rich

Duh. Sell them to some other sucker on Ebay. ;-P

Good Luck! Rich

On 2 Jan 2006 14:13:04 -0800, logjam blurted:

Sell them on EBay ?? Spamming this account signifies your unqualified consent to a free security audit

This started as a little thought. Now I'm kind of excited about it!

Rather than have gaps all over the place I've designed it to have LEDs that are always off in binary view mode. Labels could be placed over the dead LEDs. Then in a normal mode the display could be used as a giant bitmapped display. This might make the LED wall more attractive to other people. ;)

I know, I messed up on all the captions. The COST is correct. $255 vs $350

1296 bytes 400 mil spacing, 10368 bits of display, 4212 LEDs wasted in binary view mode

1280 bytes

300 mil spacing, 10240 bits of display, 4160 LEDs wasted in binary view mode

The 400mil display would be a 180x81 pixel display. The 300mil display would be a 160x90 pixel display.

Here is a photo of a 400 mil spaced board that I hand made.

It is 22x26 I think, 572 LEDs.

I never finished it. I decided that if I ever finished the proect I would buy the PC boards. :)

^^^^^^

Ah, that explains it. Winter darkness... You crave LIGHT!

-- Regards, Bob Monsen

"False facts are highly injurious to the progress of science, for they often endure long; but false views, if supported by some evidence, do little harm, for every one takes a salutary pleasure in proving their falseness." -- Charles Darwin

I'm in Anchorage Alaska.

Another benefit of the RamWall is getting your room to look like part of a borg space ship! :)

I had the 30x27 grid done, but then I remembered about a project I did back in high school. I made a 8x11 character display that was big enough to handle nice fonts. So to make the board more usable, I changed it to a 30x33 grid. Then I decided that someone might only want one row of characters not 3, so I designed the board so that it could easily be cut into 3 pieces and reconfigured in any way desired. :)

The circuit board ended up being 12x13.2. a 30x33 grid cost the same as 30x27, but it did take an extra 7,000 or so LEDs to fill in the new space. There are 990 LEDs per circuit board and 18 circuit boards in my display.

I should be able to display a NICE terminal font on the display, 9 rows

- 22 characters per row. Using a TINY font like those little store signs and I should be able to fit 14x36, which is barely big enough for lynx, wouldn't that be fun to see? :) Browse the web in green LEDs...

Here is one of the 3 rows:

Here are all 3 rows:

The new finished dimensions are:

72 inches wide 40 inches tall

What do you think now? Too late to change my mind, the PCBs are ordered. :D