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strange LCD display

M

merco

Jan 1, 1970
0
here is a display grabbed from an old (90's) telephone...
http://i1.tinypic.com/n4td3b.jpg

How can i guess it's pinout ?
I think it has 12 character + 8 fixed messages on/off type (save,
redial,alarm, memo, lower , program , am, pm)

Any suggestions ?

thanks in advance...
 
J

John Fields

Jan 1, 1970
0
here is a display grabbed from an old (90's) telephone...
http://i1.tinypic.com/n4td3b.jpg

How can i guess it's pinout ?
I think it has 12 character + 8 fixed messages on/off type (save,
redial,alarm, memo, lower , program , am, pm)

Any suggestions ?

---
From your description and the number of pins available, it would be
a multiplexed display and it would need seven pins for the [seven
segment] characters, 8 pins for the various annunciators, and 13
pins for the backplanes. It has 28 pins, so that's consistent with
your description, which is a good thing. :)

In order to find out what's what you'll need to find the backplanes
and then drive the segments and annunciators out of phase with their
respective backplanes, ideally with a 50% duty cycle square wave at
about 30Hz.

An easy way to do that would be to use a 7555 to get the 50% duty
cycle square wave at 30Hz, and then invert that signal to get the
out-of-phase signal you also need, like this:




+----[100k]---+------------->PHASE0
| +-------+ |
+--|TH OUT|--+----[INV]O--->PHASE1
| |___ _|
+-O|DIS R|O--+5
| +-------+
[0.22µF] 7555
|
GND

Then, connect PHASE0 to pin 1 of the display and probe the rest of
the pins with PHASE1. Eventually, one or more of the segments or
annunciators should become visible. If more than one becomes
visible, then PHASE0 is on a backplane, and you should be able to
identify all of the segments or annunciators with PHASE1. Once
you've identified the segments, you can connect one of the phases to
it and use the other phase to find the remaining backplanes by
watching the segment jump from one position to another when you
connect to the various backplanes.
 
M

merco

Jan 1, 1970
0
I've done your test, but probably i don't understand very well, sorry i
can't speak english...
Not only 1 segment is ON every PIN i touch..
maybe you could explain it with a simple schematic ?
 
J

John Fields

Jan 1, 1970
0
I've done your test, but probably i don't understand very well, sorry i
can't speak english...
Not only 1 segment is ON every PIN i touch..
maybe you could explain it with a simple schematic ?

---

I'm sorry, I don't know how to do that, but maybe you have a friend
who can speak English or maybe someone here who can speak Italian
(?) can translate it for you?

In any case, it seems you understand some stuff, so let's try to
make sure your phase generator is working.

+-------------+------------->PHASE0
| +5V |
[100K] |1 |
| +---+---+ |
+--|TH OUT|--+----[INV]O--->PHASE1
| |___ _|
+-O|DIS R|O--+5V
| +---+---+
[0.22µF] |8
| |
GND GND

Do your phases look like this?:

_ _ _ _
PHASE0 __| |_| |_| |_| |_
__ _ _ _ _
PHASE1 |_| |_| |_| |_|
 
M

merco

Jan 1, 1970
0
first question:
i have only sn74act04 available is it good for this purpose ?

Vcc=5 volt is good for our Lcd diplay ?

and , by the way... why do u think i'm italian ? ;-)
 
M

Michael A. Terrell

Jan 1, 1970
0
merco said:
first question:
i have only sn74act04 available is it good for this purpose ?

Vcc=5 volt is good for our Lcd diplay ?

and , by the way... why do u think i'm italian ? ;-)

inetnum: 151.30.0.0 - 151.30.255.255
netname: LIBERO-INFOSTRADA
descr: Free Internet Dial-up Services
descr: Via Lorenteggio 257 - 20152 Milano
country: IT
admin-c: AN2056-RIPE
tech-c: AN2056-RIPE
status: ASSIGNED PA
mnt-by: AS1267-MNT
mnt-lower: AS1267-MNT
mnt-routes: AS1267-MNT
source: RIPE # Filtered
person: Abuse Notification
address: Via Lorenteggio 257
address: I-20152 Milano
address: Italy
phone: +39 02 41331
e-mail: [email protected]
e-mail: [email protected]
nic-hdl: AN2056-RIPE
source: RIPE # Filtered
% Information related to '151.30.0.0/16AS1267'
route: 151.30.0.0/16
descr: INFOSTRADA
origin: AS1267
remarks: removed cross-mnt: AS1267-MNT
mnt-lower: AS1267-MNT
mnt-routes: AS1267-MNT
mnt-by: AS1267-MNT
source: RIPE # Filtered

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
M

merco

Jan 1, 1970
0
ok, it's me .. or better... it's my dial up service provider ;)
 
M

Michael A. Terrell

Jan 1, 1970
0
merco said:
ok, it's me .. or better... it's my dial up service provider ;)


Well, you did ask, didn't you? ;-)


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
M

merco

Jan 1, 1970
0
i've done some tests but for example starting from pin2 to pin 28 i get
more tha 1 segment on for single "character"...
pin2 = phase0
pin5= phase1
output character 1 : "L" + fixed message (dial)
pin2 = phase0
pin6= phase1
output character 1 : "7"
and so on
pin2 = phase0
pin7= phase1
output character 1 : "L" + fixed message (mem)
pin2 = phase0
pin8= phase1
output character 1 : "7"
 
M

merco

Jan 1, 1970
0
i can't give 3 volts supply at sn74act04 it requires from 4.5V to 5.5V
 
J

John Fields

Jan 1, 1970
0
i've done some tests but for example starting from pin2 to pin 28 i get
more tha 1 segment on for single "character"...
pin2 = phase0
pin5= phase1
output character 1 : "L" + fixed message (dial)
pin2 = phase0
pin6= phase1
output character 1 : "7"
and so on
pin2 = phase0
pin7= phase1
output character 1 : "L" + fixed message (mem)
pin2 = phase0
pin8= phase1
output character 1 : "7"

---
Excellent! Now you know the display isn't dead.

Probably what you should do now is make a map of the display.

That is, starting with phase0 on pin 1, probe all of the other pins
with phase1 and write down what you find. Then disconnect phase0
from pin 1, connect it to pin 2 and probe all of the other pins with
phase1, again writing down what you find. Continue that way until
you run out of pins to probe and you'll know what it takes to turn
on the various segments. Or maybe it's character oriented? I don't
know, but you'll need to find out what's what in order to be able to
decide whether you can use the thing or not.

Instead of just writing down what you find, it might be a good idea
to set up a spreadsheet, like this:


PHASE0 -> | PIN1 | PIN2 | PIN3 | PIN4 | . . .| pin28|
PHASE1 +------+------+------+------+ +------+
PIN1 | | | | | | |
----------+------+------+------+------+ +------+
PIN2 | | | | | | |
----------+------+------+------+------+ +------+
PIN3 | | | | | | |
----------+------+------+------+------+ +------+
PIN4 | | | | | | |
----------+------+------+------+------+ +------+
 
M

merco

Jan 1, 1970
0
excel... ??

but in the cell PIN1 / PIN3 i have 4 segment ON in first space
(character L + fixed message)
but in the cell PIN1 / PIN4 i have 4 segment ON in first space
(character 7: the 4 chars remaining )

and so on
it isn't so clear for me... Each pin seems to put ON more than 1 led
per character...
 
J

John Fields

Jan 1, 1970
0
excel... ??

---
Sure, why not?
---
but in the cell PIN1 / PIN3 i have 4 segment ON in first space
(character L + fixed message)
but in the cell PIN1 / PIN4 i have 4 segment ON in first space
(character 7: the 4 chars remaining )

and so on
it isn't so clear for me... Each pin seems to put ON more than 1 led
per character...

---
It may be that the characters are built up by multiplexing some of
the segments and backplanes in unusual ways, in which case you might
have an interesting decoding problem on your hands.

But, first things first, so why don't you go ahead and probe the
whole array and see whether you can make any sense out of it?
 
M

merco

Jan 1, 1970
0
ok, but it's a little boring... isn't it ? :(

I think some pins are not connected...
 
J

John Fields

Jan 1, 1970
0
ok, but it's a little boring... isn't it ? :(

---
Hey, it's _your_ project. Abandon it at any time, if you like. I
won't mind at all...
---
I think some pins are not connected...

---
Well, if you connect the phases between two segments (or characters,
or annunciators) or between two backplanes, you won't see anything.

You have to find the backplanes and then probe the rest of the pins
to see what happens.

You might want to Google "How LCDs work" to find out how LCDs work.
 
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