strange LCD display

--- 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.

-- John Fields Professional Circuit Designer

thank you for your reply.

I've found some news about that and probably an ugly schematic... su un sito russo ho scaricato un PDF con lo schema:

su un sito russo ho scaricato un PDF con lo schema: watch a detail here IC5 is a 2C1 VU404616fs A04 japan...

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 |_| |_| |_| |_|

-- John Fields Professional Circuit Designer

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 ? ;-)

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Member of DAV #85.

Michael A. Terrell
Central Florida

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

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"

--
What purpose?

i can't give 3 volts supply at sn74act04 it requires from 4.5V to 5.5V

--- 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 | | | | | | |

----------+------+------+------+------+ +------+ .

----------+------+------+------+------+ +------+ pin28 | | | | | | |

----------+------+------+------+------+ +------+

Enter what you find in the appropriate cells, and when you get finished you'll have everything you need right in front of you.

-- John Fields Professional Circuit Designer

--- What I meant was that 5V will be fine for testing, but when you get the display into what you want to use it in, you may want to use a lower voltage on it.

-- John Fields Professional Circuit Designer

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...

--
Sure, why not?

ok, but it's a little boring... isn't it ? :(

I think some pins are not connected...

--
Hey, it\'s _your_ project.  Abandon it at any time, if you like.  I
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