help with Calculator LCD - Electronic Circuits Projects Diagrams Free

aryyy · 16th July 2006, 06:53 AM

i am trying to connect a simple calculator 10 digit display to 8051(AT89S51) ... i ripped it from a broken calculator... it has 32 wires.... please help ... calculator was a KADIO...

Death By Bass · 16th July 2006, 08:10 AM

connect to what?

hjames · 17th July 2006, 07:36 AM

LCD "glass" is slightly tricky to drive - there are microcontrollers which have built in LCD drive components for numeric displays like the one you mentioned. Segments turn on if there is a voltage across it's leads, but a static DC voltage will damage the segment - so it needs to be driven by AC signal. Bit-banging the signals is defintely doable, but it is a hassle.

Can you trace how many of the LCD pins are actually connected? Unlike LED displays, LCD glass tends to be wired up in exceptionally weird ways. (Mostly because of the AC drive + duty cycle requirements, and also because of the oddball symbols they tend to put on there. For some examples, take a look at the datasheets available on the Varitronix website:

http://www.varitronix.com/LCDsearch....ery1=no&page=7
(for example, an 6 digit LCD glass has 3 common lines and 24 segment lines...)

I don't have any experience with the AT89S51, but I'd guess that you'll need to add at least two external latch chips unless you want to tie up all the IO lines. Plus, I hope the LCD glass you want to use is one with actual pins on it and not the elastomer "zebra" strips, otherwise you'll need to make a PC board for it.

Oznog · 17th July 2006, 09:51 AM

You really, really want to just get an LCD module with a controller built into it. Then you can just do read/write instructions to the display.

Everybody asks about how to use these junk controller-less LCDs. It's simply not practical, I've never heard of anybody ever doing it. A microcontroller would have a really, really hard time, you'd spend more $ and far more time than just doing the module. But like I say I've never even heard of someone getting it to work.

atferrari · 17th July 2006, 10:24 AM

Probably not that from a calculator but from portable phones, yes. There are some examples, said to be working (?), if you search the web.

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16th July 2006, 06:53 AM	(permalink)
aryyy	help with Calculator LCD i am trying to connect a simple calculator 10 digit display to 8051(AT89S51) ... i ripped it from a broken calculator... it has 32 wires.... please help ... calculator was a KADIO...

16th July 2006, 08:10 AM	(permalink)
Death By Bass	connect to what?

17th July 2006, 07:36 AM	(permalink)
hjames	LCD "glass" is slightly tricky to drive - there are microcontrollers which have built in LCD drive components for numeric displays like the one you mentioned. Segments turn on if there is a voltage across it's leads, but a static DC voltage will damage the segment - so it needs to be driven by AC signal. Bit-banging the signals is defintely doable, but it is a hassle. Can you trace how many of the LCD pins are actually connected? Unlike LED displays, LCD glass tends to be wired up in exceptionally weird ways. (Mostly because of the AC drive + duty cycle requirements, and also because of the oddball symbols they tend to put on there. For some examples, take a look at the datasheets available on the Varitronix website: http://www.varitronix.com/LCDsearch....ery1=no&page=7 (for example, an 6 digit LCD glass has 3 common lines and 24 segment lines...) I don't have any experience with the AT89S51, but I'd guess that you'll need to add at least two external latch chips unless you want to tie up all the IO lines. Plus, I hope the LCD glass you want to use is one with actual pins on it and not the elastomer "zebra" strips, otherwise you'll need to make a PC board for it.

17th July 2006, 09:51 AM	(permalink)
Oznog	You really, really want to just get an LCD module with a controller built into it. Then you can just do read/write instructions to the display. Everybody asks about how to use these junk controller-less LCDs. It's simply not practical, I've never heard of anybody ever doing it. A microcontroller would have a really, really hard time, you'd spend more $ and far more time than just doing the module. But like I say I've never even heard of someone getting it to work. __________________ I thought what I'd do was I'd pretend I was one of those deaf-mutes.

17th July 2006, 10:24 AM	(permalink)
atferrari	Probably not that from a calculator but from portable phones, yes. There are some examples, said to be working (?), if you search the web. __________________ Agustín Tomás In theory, there is no difference between theory and practice. In practice, however, there is.