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'36 inch tall LED digits.'
1998\07\27@133737 by Troy P.

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Hi all,
I have an opportunity make a little money if I can design a display that
has 5 - 36" tall digits on it. I have always wanted to make one of these
anyway but I wanted to do it with LEDs. Does anyone have any experience
with this type of design. Questions that came to my mind were:
1. What should the width of each segment be? The height will be 18".

2. What should the spacing on the LEDs be? I was thinking about
stagering them for more coverage.

3. How should the current and voltage be made? First calculations show
about 30amps at around 5v per digit. This didn't sound right to me. This
was based on 8LEDs/square inch and each segment being 18" x 2" and this
seems too skinny.

Any thoughts will help before I start spending money on development.

Thanks in advance.
Troy Powledge
TCo. Systems
spam_OUTtpowTakeThisOuTspameramp.net

1998\07\27@151946 by Format

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Cool =)
Using LED bars would be my idea, just take the proportions of regular LED 7
segment cases and apply it.

Troy P. wrote:

{Quote hidden}

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1998\07\27@153903 by Dan Larson

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On Sun, 26 Jul 1998 21:08:51 -0500, Troy P. wrote:

>Hi all,
>I have an opportunity make a little money if I can design a display that
>has 5 - 36" tall digits on it. I have always wanted to make one of these
>anyway but I wanted to do it with LEDs. Does anyone have any experience
>with this type of design. Questions that came to my mind were:
>1. What should the width of each segment be? The height will be 18".
>
>2. What should the spacing on the LEDs be? I was thinking about
>stagering them for more coverage.
>
>3. How should the current and voltage be made? First calculations show
>about 30amps at around 5v per digit. This didn't sound right to me. This
>was based on 8LEDs/square inch and each segment being 18" x 2" and this
>seems too skinny.

Might I suggest *multiplexing* the segments!  <VBG>  Then you won't need
000 gauge wire to feed them.. Perhaps divide the LEDS into other groups
that scatter them throughout the display then mutiplex each group.  That
way some of the LEDS would be on in each segments at any given time.

Look at LED clusters that are sold as replacements for incandescent
indicator lamps.  I have seen them in many catalogs.

>
>Any thoughts will help before I start spending money on development.
>


Dan

1998\07\27@163240 by Mark Willis

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(I mumble about clocks as that's MY use for this, it's the idea that
counts <G>)

 One option:  Laser scanner projects the digits onto a flat surface, "a
la" those cheap surplus red laser scanner mechanisms, this might be much
cheaper than all those LEDs (for hardware costs anyways!) & would be
really visible indoors (if no human's in the beam path!)  Or fairly
visible outdoors in shadow.  I've been mumbling about building this for
large-digit house clocks since my favorite clocks were discontinued
(drat!)  If you have a continuous-on laser, use a mask to block the
light beam when no output desired.  (i.e. 2 voicecoils, one for H
aiming, one for V aiming, when you don't want light output aim the laser
down out of the open hole in the mask.)

 That might be far cheaper, & take less power, than a bunch of LEDs.
And you could also spread out the scans into multiple parallel scans if
needed, for more visibility?  Or use one laser per digit (for a 5 digit
display, 5x the light available to dump onto the surface) for a brighter
clock.  Would take more development time, potentially.

 As laser beams are quite visible, at quite a distance, I'm also
wondering: do you NEED 2" wide groups of LEDs, or just a single row?
(Anyone done this?  I've been thinking of playing with it, my
girlfriend's physically disabled & partially visually disabled, and I'm
a little nearsighted, so for convenience for us both it'd be neat to
have a large digit clock in each room, networked to the master clock,
always easily visible & on time!  I could go 12" clocks from one laser,
indoors...)

 Mark Willis, mwillisspamKILLspamnwlink.com

Troy P. wrote:
{Quote hidden}

1998\07\27@171311 by Martin Walton

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>  3. How should the current and voltage be made? First >  calculations
show about 30amps at around 5v per digit. This >  didn't sound right to me.


When I do this kind of thing I usually connect blocks of LEDs in series and
run them off a higher voltage, say 24V.  This keeps the current down and
also the cost of the transistors doing the switching.

Martin

1998\07\27@171659 by Reginald Neale

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Mark:

I, too am interested in clocks, and in PIC and STAMP approaches to
improving them. I found a circuit on the web for receiving the European
standard time signal and using it to update a display. Are you aware of any
similar circuit for WWVB?

Regards,
Reg

1998\07\28@010538 by Mark Willis

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I know I've seen a bunch of non-PIC, non-stamp, WWV/WWVB time signal
grabbers in the past, but I haven't been looking lately;  It's a good
project!  Heathkit used to sell such a device, I know some other
projects used micros, back in the '70's there were 7400 series projects
<G>

 I'd think a search of past Electronics Today, Popular Electronics,
Circuit Cellar, etc. issues would turn up something which could be
adapted and/or re-worked, I've been stymied on displays but now maybe I
have a good idea <G>

 I think that using one laser scanner for horizontal lines, and the
other for vertical lines, is the easiest answer here.  That just might
work <G>  Less work than having to scan both ways with one beam...

 Mark

Reginald Neale wrote:
{Quote hidden}

1998\07\28@051523 by wwl

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On Sun, 26 Jul 1998 21:08:51 -0500, you wrote:

{Quote hidden}

To keep the current down ( hence wiring sensible & losses down), you
may want to use a relatively high voltage (50V +) to drive a lot of
LEDs in series - each seg will have loads of LEDs so this shouldn't be
a problem. For efficiency, you may want to use a switchmode
constant-current source instead of resistors.  
If you have a real lot of LEDs, how about wiring enough in series for
mains voltage operation and controlling with triacs.

    ____                                                           ____
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_/ W_/  Hardware & Software design / PCB Design / Consultancy  _/ W_/
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1998\07\28@065236 by Keith Howell

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The BBC did a series called "The Secret Life of Machines", with the aid
of some chaps who produce illustrative cartoons in "New Scientist"
magazine. Tim Hunkin I think the name is.

One programme about the quartz watch showed the oscillator driving a
counter driving a logic chip and eventually the power into a set of
strip lights. Arranged in the familiar 7-seg pattern, they showed the
time.

I thought this was a cute way of building a very big digital clock.
Instead of driving the LEDs of a seven segment display, the  decoder can
drive the LEDs of opto-coupled triacs switching the mains.

I think controlling the power into filament strip lights may be easier
than the more efficient flourescent ones.

You could put them into a black box with 7-segs cut out and behind that
a translucent diffuser - white, red, green, or even blue!

------------------------------------------------------------
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Every time I go for a piss, the sinks full of dirty plates!"
------------------------------------------------------------

1998\07\28@130916 by wwl

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On Tue, 28 Jul 1998 11:33:27 +0100, you wrote:

>The BBC did a series called "The Secret Life of Machines", with the aid
>of some chaps who produce illustrative cartoons in "New Scientist"
>magazine. Tim Hunkin I think the name is.
>
>One programme about the quartz watch showed the oscillator driving a
>counter driving a logic chip and eventually the power into a set of
>strip lights. Arranged in the familiar 7-seg pattern, they showed the
>time.
>
>I thought this was a cute way of building a very big digital clock.
>Instead of driving the LEDs of a seven segment display, the  decoder can
>drive the LEDs of opto-coupled triacs switching the mains.
>
>I think controlling the power into filament strip lights may be easier
>than the more efficient flourescent ones.
But long filament lamps are unreliable.
    ____                                                           ____
  _/ L_/  Mike Harrison / White Wing Logic / @spam@wwlKILLspamspamnetcomuk.co.uk  _/ L_/
_/ W_/  Hardware & Software design / PCB Design / Consultancy  _/ W_/
/_W_/  Industrial / Computer Peripherals / Hazardous Area      /_W_/

1998\07\29@163155 by Stuart Broad

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-----Original Message-----
From: Troy P. <KILLspamtpowKILLspamspamERAMP.NET>
To: RemoveMEPICLISTTakeThisOuTspamMITVMA.MIT.EDU <spamBeGonePICLISTspamBeGonespamMITVMA.MIT.EDU>
Date: 27 July 1998 18:41
Subject: 36 inch tall LED digits.


>Hi all,
>I have an opportunity make a little money if I can design a display that
>has 5 - 36" tall digits on it. I have always wanted to make one of these
>anyway but I wanted to do it with LEDs. Does anyone have any experience
>with this type of design. Questions that came to my mind were:
>1. What should the width of each segment be? The height will be 18".
>
>2. What should the spacing on the LEDs be? I was thinking about
>stagering them for more coverage.
<snip>

For this type of display and the light output required I would strongly
suggest making an enclosure and back light each segment with mains driven
incandescent lamps.
I've seen very effective 7 segment displays made up from 12" linear tungsten
lamps with an opto isolated triac drive for each segment.

Regards

Stuart Broad.

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