5 replies to this topic

[jose3]

Hi,

When I was in primary school, that is in the early 80s, I used the Casio calculator with electroluminescent backlight a friend owed.

Some time ago I decided to buy it. First I searched for it becouse it was just a vague remember in my mind. For my surprise it seems it never existed. I have spent months searching but nothing. I even contacted Casio Japan, Casio US and Casio UK, but they wrote me that calculator was never produced. So I hope to find someone here who ever used it.

It was a Casio very similar to the old FX 82, with square lines and two AA batteries, but slightly bigger. The digits were bigger too. The most impressive feature was that the calculator had a yellow green electroluminescent backlight. Actually when you swiched the machine on, the screen came on like in a normal calculator; there was an extra key on top of the display, when you pressed it, the backlight came on and the lcd digits changed from possitive to negative, so the digits themself had colour like in a VFD display. This invertion of the display was not perfect, so the rest of the display was dark green or yellow, not black.
The logo "ELECTROLUMINESCENT" was printed very clear on top of the display.
When I used it, I thought: "nice, they'll make more for sure". But that was the only time in my life I saw one of those.

After searching for months, not only I didnt find it, but I learnt that no one have ever produced a scientific calculator with backlight display to emule (very readable) VFDs displays, even when the electroluminescent technology is available from the sixthies at least !
If you think propperly, the calculator that I described was ideal: it can have a low power normal display, or it can display bright phosphorescent digits, much more easy to read, and it got advantage of the people stil getting used to big calculators with AA batteries to feed the electroluminescent panel (later manufactured realized the batteries corroded before they run out, in a normal lcd machine, becouse they worked for years).

Today I think there are two possibilities about the calculator I saw: or it was a prototype produced in very small quantities and never went into mass production. Or it was a fake clone someone invented taking advance of Casio brand.
There is, of course, a third option and is that I made the calculator in my mind and it became a remember (It means I'm crazy :-| or so), which is possible cos this happened 20 years ago and I was very young. But I dont think so.

Of course I seached another brands for this calculator; as I said, I have been seaching for month. The result have been the same so far.

Now I am in the process to modify a FX 82 to make a calculator as I described. I love this machine becouse it has the on-off function on a switch that I'll use to power the backlight too (you can not do this in a machine with on-off on the keyboard). There's so much space under the display that probably I'll use LED backlighing, so I'll be able to select from a number of colours. This is a project that wont include the normal-diplay operation, becouse I dont know how to invert an LCD display.


Does anyone saw the this Casio scientific calculator with Electroluminescent display too?


Jose

[Xerxes]

The only CASIO calculator with electro luminescence display I know is the FX-135.



Picture from: http://www.casio-museum.eu

[jose3]

Amaizing ! I just can not belived what I see.

Thank you Xerxes.

It is most likely this one ! I dont see the key to switch on the electroluminecent display, so I have a doubt.
The screen is black: apparently it works with the backlight all the time.

Do you own this machine or did you have the chance to use it? Can you confirm it works like a normal lcd untill you turn on the backlight?

Mmmm, I was thinking may be it was so long ago and I remembered wrong and possible it works on backlight all time !

This photo helped me a lot. Now I'll try find it and buy one.

jose

[Xerxes]

I bought the FX-135 about 15 years ago and used it for a short while. If I remember correctly
there is no backlight switch. The display itself is a normal LCD but reversed (light digits on
dark backround) with greenish backlight.

Unfortunately the FX-135 is quite rare and very hard to find, but good luck for finding this
nice calculator.

[Vinx]

Yeah, the word 'ELECTROLUMINESCENT' refers to material that emit light when electric current pass through it.
for calculator screens, we call it 'LED'.

When I was studying at the university (>15 year ago), one of my friend use CASIO fx-7? (can't remember the model no. exactly but rather sure it's not fx-135) which use LED screen and he himself was a math geek, sometime he even used his calculator to compute something in the darkness. Another thing I remember is it's very large (~11 inch. in length) and work with AA batteries, I think that's cool because at that time I used fx-7700GB which take 4xCR2032 batt. to run (very expensive at that time).

Edited by Vinx, 17 November 2009 - 03:47 PM.

[jose3]

Vinx,

LED displays were used by Hewlett Packar and Ti. They later changed to LCD displays.
Casio used VFD displays at the begining and later passed to LCDs and if I'm not wrong, they didnt use LEDs in their calculators.
LEDs are easily recognizable becouse they are red. VFD came in blue-green and blue colour. They both can be read in the dark, but they are quite different tecnologies. They were very popular at their time.

The display I opened this threat about, electroluminescent, is different to LEDs or VFD. It uses a material thin like a paper in between two catods, that emits lights when a high voltage is applied.
This tecnology never became popular becouse of the advent of LCD. That's what makes the F 135 so unic. Only one company, Planar, continued developing electroluminiscent displays for medical aplications, at very high prices. But these are matrix displays and a seven segments electroluminescent display was neved on the market for calculators. As Xerxes mentioned the F 135 had a reversed LCD as screen. The electroluminescent panel was for backighting.

You can find a lot of interesting stuff on wikipedia about the calculator you saw.

jose