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'[EE]: Identifying pins on unknown 7-segment LED'
2003\04\10@124057 by John Nall

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A friend (?) has given me a bag of about a 100 seven-segment LED's which
he said he found while cleaning out his workshop.  He doesn't know what
they are and says that they probably date back to the mid 1980's
sometime. :-(

I'd like to be able to use them in miscellaneous projects if I can
identify which pins are which.  I can try trial and error, since there
are a lot of them, but thought I would take a chance and see if someone
on this list might be able to point me to a datasheet, or something like
that.

They are 3/4" high by 3/8" wide, red in color.  They are in the shape of
a 14-pin IC.  Looking into the face, there are two indentations at the
bottom and a single indentation at the top, with a dimple at the top
left (probably to identify pin 1).  Assuming this is pin 1, then there
is a pin 1, 2, 3 and 4.  No pin 5.  Pin 6 and 7.  Continuing to the othe
side, there is pin 8, 9, 10.  No pin 11, no pin 12. Pins 13 and 14.

There is absolutely no marking of any sort to indicate the manufacturer
or  the model number.  (I have examined it with a magnifying glass under
a strong light).

Thanks for any help.

John

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2003\04\10@124853 by Ned Konz

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On Thursday 10 April 2003 09:41 am, John Nall wrote:
> A friend (?) has given me a bag of about a 100 seven-segment LED's
> which he said he found while cleaning out his workshop.  He doesn't
> know what they are and says that they probably date back to the mid
> 1980's sometime. :-(
>
> I'd like to be able to use them in miscellaneous projects if I can
> identify which pins are which.  I can try trial and error, since
> there are a lot of them, but thought I would take a chance and see
> if someone on this list might be able to point me to a datasheet,
> or something like that.
>
> They are 3/4" high by 3/8" wide, red in color.  They are in the
> shape of a 14-pin IC.  Looking into the face, there are two
> indentations at the bottom and a single indentation at the top,
> with a dimple at the top left (probably to identify pin 1).
> Assuming this is pin 1, then there is a pin 1, 2, 3 and 4.  No pin
> 5.  Pin 6 and 7.  Continuing to the othe side, there is pin 8, 9,
> 10.  No pin 11, no pin 12. Pins 13 and 14.

Does this help? Remember that it could be either common anode or
common cathode...

http://www.iguanalabs.com/7segment.htm

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2003\04\10@124901 by PicDude

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Sorry, can't identify for you, but it might make for an
interesting PIC project -- a device that you plug one
of these into, and it trial-and-errors for you measuring
the current/voltage drop etc.

Cheers,
-Neil.



> {Original Message removed}

2003\04\10@125936 by Quentin

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Hi John
First, try places like agilent.com and books/CD's like RS Electronics
and Farnell. You might just find a generic.
Your pin out sounds familiar (ie: I've seen it before).
or:
If you can test an LED, you can figure out the pinouts quickly (without
destroying one). A multimeter set on diode test or ohms will pass a low
voltage through the LED and most of the time, you will see the LED come
on (glow). Play around until you get an LED segment to come on, then
decide which pin is common (C or A) then you can go through all the pins
to figure out the segments.
Since you got 11 pins, that gives you 7 segments +DP, +common=9. Most
likely the two remaining pins are also common or N/C.

Hope this helps.
Quentin

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2003\04\10@130151 by Wouter van Ooijen

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> I'd like to be able to use them in miscellaneous projects if I can
> identify which pins are which.  I can try trial and error, since there
> are a lot of them, but thought I would take a chance and see
> if someone
> on this list might be able to point me to a datasheet, or
> something like
> that.

Just 'crush' one, there is probably a PCB like thingy inside, from which
you can find the common and segment pins. Now you only have to try for
CC or CA.

And anyway, even without looking inside trial-and-error takes only a
minute or two. Just done that on a 3.5 digit display in 5 minutes.

Wouter van Ooijen

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2003\04\10@131810 by Olin Lathrop

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> I'd like to be able to use them in miscellaneous projects if I can
> identify which pins are which.  I can try trial and error, since there
> are a lot of them,

That should be very easy to do, however.  Probe around with 12VAC and
1Kohm in series.  You shouldn't be able to do any damage with that.  The
AC will light up LEDs regardless of direction.  Short one side of pins
together connected to one AC side, then probe individual pins with the
other.  You should be able to find the common anode or cathode in well
under a minute.  Once you've got that, switch to DC to figure out which,
then just pins to segments.  This really shouldn't take more than a couple
of minutes.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

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2003\04\10@132704 by Byron A Jeff

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On Thu, Apr 10, 2003 at 12:41:11PM -0400, John Nall wrote:
> A friend (?) has given me a bag of about a 100 seven-segment LED's which

> They are 3/4" high by 3/8" wide, red in color.  They are in the shape of
> a 14-pin IC.  Looking into the face, there are two indentations at the
> bottom and a single indentation at the top, with a dimple at the top
> left (probably to identify pin 1).  Assuming this is pin 1, then there
> is a pin 1, 2, 3 and 4.  No pin 5.  Pin 6 and 7.  Continuing to the othe
> side, there is pin 8, 9, 10.  No pin 11, no pin 12. Pins 13 and 14.
>
> There is absolutely no marking of any sort to indicate the manufacturer
> or  the model number.  (I have examined it with a magnifying glass under
> a strong light).

John,

It takes less that two minutes to ID all of the pins. All you need is a DC
power supply and a current limiting resistor. Make sure that the resistor
won't pass more than 10ma of current when dropping the whole voltage of the
supply. So for 5V use 5V/0.1 -> 500 ohms (470 is fine). This will light the LED
but protty much guarantees that it won't blow out an LED no matter the
current rating.

Create a probe by tying the resistor to the V+ lead of the supply, and a lead
to the GND. Take one end and tie to pin 1. Drag the other across all the other
pins. If any segment lights up then you have a starting point. If not then
move the fixed end from pin 1 to the next pin.

Generally within 30 seconds you'll get a segment to light up. If the floating
end of the probe lights up any other segment, then the fixed end is the common.
Otherwise the floating end is the common and you start IDing with the fixed
end.

In any case you can completely ID the entire display in about 2 to 3 minutes.

I never both keeping pinouts on LED displays because they are so easy to ID.

BAJ

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2003\04\10@175205 by William Chops Westfield

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   It takes less that two minutes to ID all of the pins. All you need is a DC
   power supply and a current limiting resistor.

My initial thought was that this sounded like a TIL311 (hexadecimal display
with internal logic.  But the missing pins are in the wrong place.)  The
sort of tests being propose will NOT work on that sort of device (of course,
"that sort of device" is pretty rare...)

BillW

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2003\04\10@200154 by John Nall

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At 02:51 PM 4/10/2003 -0700, BillW wrote:
>     It takes less that two minutes to ID all of the pins. All you need is
> a DC
>     power supply and a current limiting resistor.
>
>My initial thought was that this sounded like a TIL311 (hexadecimal display
>with internal logic.  But the missing pins are in the wrong place.)  The
>sort of tests being propose will NOT work on that sort of device (of course,
>"that sort of device" is pretty rare...)
>
>BillW

Actually, the proposed tests did work OK, once I got over the shame and
embarrassment of not realizing that I could do that BEFORE asking for help.
:-)    The device does not have a common anode (nor a common cathode) but
instead has THREE common anodes!  (Of course, these can easily be made into
a common anode).  The led itself, embedded (like unto a reporter) in the
chip is a tiny little thing, possibly having some historical value to
people who are interested in the development of 7-segment displays.  The
fellow who gave them to me said that he originally bought them from a
person named "Bill Godbout" (I am not sure if this was an actual person,
or  the name of a company) who got them surplus from somewhere.  At any
rate, I have gunned them out, and once again proclaim the value of Internet
communication (with all its warts).

John

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2003\04\10@235513 by Russell McMahon

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> instead has THREE common anodes!  (Of course, these can easily be made
into
> a common anode).  The led itself, embedded (like unto a reporter) in the

Does this mean that the display is viewable almost solely from one side
only, distorts what you see, fails to display almost anything viewed from
the other side, provides views with an interesting perspective, can't be
relied on for accurate data, .... ? :-)



   RM


(I think I may yet regret this one :-(  ).

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2003\04\11@020927 by William Chops Westfield

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   The fellow who gave them to me said that he originally bought them from
   a person named "Bill Godbout" (I am not sure if this was an actual
   person, or the name of a company) who got them surplus from somewhere.

Heh.  Both.  Bill Godbout ran "Godbout electronics", an early heavy player
in the S-100 CPM computer world.  Bought a bunch of stuff from him a long
time ago, and never quite got it working :-( (not his fault...)  I wonder
if my S100 "system" is still sitting in storage over at Stanford somewhere?

A web search turns up lots of early history.  Apparently Godbout become
CompuPro, and did generic surplus before focusing on computers...

BillW

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2003\04\11@025538 by Jason Harper

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John wrote:
> The device does not have a common anode (nor a common cathode) but
> instead has THREE common anodes!

Each anode has 2-3 separate cathodes, I assume?  If so, I see some
interesting possibilities here - you could drive one of these things with
1/3 multiplexing using 4 PIC pins and 3 resistors, that's MUCH nicer than
standard 7-segment LEDs.
       Jason Harper

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2003\04\11@074746 by John Nall

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At 03:48 PM 4/11/2003 +1200, Russell wrote:

> > instead has THREE common anodes!  (Of course, these can easily be made
>into
> > a common anode).  The led itself, embedded (like unto a reporter) in the
>
>Does this mean that the display is viewable almost solely from one side
>only, distorts what you see, fails to display almost anything viewed from
>the other side, provides views with an interesting perspective, can't be
>relied on for accurate data, .... ? :-)
>
>(I think I may yet regret this one :-(  ).

Most likely you will.  It did provide a chuckle, however. :-)   And around
these parts, we wonder if anyone thought through just how much alike
"embedded" and "in bed with" sound?

John

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