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HELP:electronic billboard

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nayr_kupal

Jan 1, 1970
0
can anyone please help me in doing my project.its an electronic
billboard running display using only logic gates and LEDs...i'm having
trouble with the design because we are not allowed to use PICs...if it
is not too much to ask, can you please send me an schematic for a
running display of the word "WELCOME"? thank you for your help
 
R

Rob

Jan 1, 1970
0
nayr_kupal said:
can anyone please help me in doing my project.its an electronic
billboard running display using only logic gates and LEDs...i'm having
trouble with the design because we are not allowed to use PICs...if it
is not too much to ask, can you please send me an schematic for a
running display of the word "WELCOME"? thank you for your help

Hello Nayr
If you are allowed only logic gates, then this is going to be a large
project. I mean that there is going to be a lot of circuitry. Are you
allowed to use counters, flip-flops and latches?
This is doable if you can use counters and latches (e.g. anything from
the '74' TTL logic range), but it will involve a lot of circuitry and
the message it displays will esentially be hardwired into it.
If can use 74 logic, will post design on website
http://notrocketscience.mysite.wanadoo-members.co.uk/ (when I get it
running).
Robert
 
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Noway2

Jan 1, 1970
0
You do realize that this is almost cerainly a project assignment for
school.

I can't think of any other reason why somebody would attempt to do this
discrete logic unless they were trying to enforce combinational and
sequential logic design.

Personally, I am getting really tired of reading "Please Send Me" from
everybody that want to be handed a design for their homework. When I
was in school, I would have been delighted just to have a usenet group
to be able to get hints from.
 
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Rob

Jan 1, 1970
0
Yes, It's obviously a school project assignment. Just had some time on
my hands and thought it sounded like an interesting thing to do.
Robert
 
C

Chris

Jan 1, 1970
0
Noway2 said:
You do realize that this is almost cerainly a project assignment for
school.

I can't think of any other reason why somebody would attempt to do this
discrete logic unless they were trying to enforce combinational and
sequential logic design.

Personally, I am getting really tired of reading "Please Send Me" from
everybody that want to be handed a design for their homework. When I
was in school, I would have been delighted just to have a usenet group
to be able to get hints from.

Yup. Probably not a direct assignment, more like a "choose your own
project". No teacher would ask students to do something like this
directly. Not only that, but this is going to be expensive.

Mr. Kupal has a couple of options, as I see it. He can go back to his
teacher and ask for another project, because this one is gonna be
"acres o' digital". One possibility more within the reach of a novice
electronics student would be getting one 16-segment alphanumeric LED
display, and then scrolling the letters at one per second, with two
blanks after the word. Still a bit of '70s digital logic, but very
doable, especially if he's allowed a couple of PROMs. And within a
student's budget, too.

Second, he can find a copy of Don Lancaster's TV Typewriter Cookbook
(Mr. Lancaster will be more than willing to send a copy
http://www.tinaja.com/books/bkdons.asp ) and look for hints as to how
to do something like this. I'd figure he's doomed unless he can use an
EPROM at least to store the data, then he can probably use a triple
counter (one for multiplexing, one for data, and another for data start
position) to achieve the scrolling effect. Not easy. There's a good
reason why these things didn't exist before microcontrollers.

The third option is to utilize this newsgroup as the OP says -- you do
the work, and send him the bill. Ask for cash in advance.

Good luck
Chris
 
B

Bob Monsen

Jan 1, 1970
0
can anyone please help me in doing my project.its an electronic
billboard running display using only logic gates and LEDs...i'm having
trouble with the design because we are not allowed to use PICs...if it
is not too much to ask, can you please send me an schematic for a
running display of the word "WELCOME"? thank you for your help

Use a mechanical 'paper tape' loop. Columns of 7 LEDs; when the hole
in the tape is under the led, it is grounded, and allows current to
flow through. Each LED should be connected to the supply through a small
resistor, the value of which is dependent on how bright you want the LED
to be. Use a little DC motor to turn the tape on a spindle. If you did it
properly, you could use the actual LED leads as the contact points. A
gearmotor that runs fairly slowly is the best way to turn it, unless you
want to get into your own gears or belts.

--
Regards,
Bob Monsen

We should take care not to make the intellect our god; it has, of
course, powerful muscles, but no personality.
Albert Einstein
 
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Rich Grise

Jan 1, 1970
0
Use a mechanical 'paper tape' loop. Columns of 7 LEDs; when the hole
in the tape is under the led, it is grounded, and allows current to
flow through. Each LED should be connected to the supply through a small
resistor, the value of which is dependent on how bright you want the LED
to be. Use a little DC motor to turn the tape on a spindle. If you did it
properly, you could use the actual LED leads as the contact points. A
gearmotor that runs fairly slowly is the best way to turn it, unless you
want to get into your own gears or belts.

Or just use the tape itself to do the scrolling. Perforate a tape that's
about 3" wide, put it in front of an EL panel or some kind of backlight,
and put a "diffuser" on the front that's got like an array of little
bumps, like a bee's eye - that'll give the strobing effect.

Cheers!
Rich
 
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