Trying to hack a calculator LCD screen

[eNathan]

New to the forums.. hello everyone

So this is what I did: took apart a calculator and took out the LCD screen to see if I can get stuff to display on it. Ultimatly I want to hook it up to a paralell port and write a program to display stuff on it or somethign nice.. but I just want to get something to display on it through sending electrical charges.. no luck... I hook up a 9V (and I've tried a small watch battery) to the tiny metal parts of the sheet that leads into the LCD.. is there something I'm missing by a million miles??

Here's a pic..

**broken link removed**

I've toyed with this for hours now.. just can't get anything, even non-sensical, to display.. any help would be great

 

[Nigel Goodwin]

It's almost certainly just a bare glass LCD, you need to drive it with AC not DC.

 

[blueroomelectronics]

Putting 9V DC through it probably killed it.

 

[eNathan]

Got it working.. what I was doing before was hooking the - and + of the battery together to try to form a "complete circuit," then putting that onto the metal strips of the LCD.. for some reason the - and + wires can't be directly toutching eachother, they have to be on two seperate metal strips.. so I did get junk to display. Only problem is that it has 28 pins.. too many for a parallel port.. so I reckon there's no way to hook it up.. so I'm looking for an LCD that has a controller built in.

It would be interesting if somebody had an explanation for why it wouldn't work when the two wires were toutching..

 

[blueroomelectronics]

Most 16x2 LCDs have controllers and can be hooked up to a printer port without too much effort.

 

[eNathan]

I'm going to go through some old electronics, maybe at a junk/thrift store down the street.. see if any old electronics have a 16x2 lcd.

 

[duffy]

There's at least one backplane signal, usually 3 or 4, and they are AC. The typical one with multiple signals uses an odd stepped voltage arrangement that used to be called something like "Pelt and Ashko multiplex" (anyone remember this?), but I can't find the reference on Google. Here's what the signals look like -
**broken link removed**

DC can kill the LCD, so can a high voltage. However, the LCD frequency is pretty liberal, and will work at 60hz. So if you get a small transformer that puts out about 3V, you can use this to activate segments if you just want to goof around with it like that.

 

[assbass]

how to

If you know microcontroller programing, this link could be useful for quadruple multiplexed (most common type) lcd:
https://www.st.com/stonline/products/literature/an/14296.pdf