My calculator has LEDs in it!
 

One day at school, I was bored, and I happened to have a knife un my binder. (just happened to have? HA!) And I used the screwdriver on it, and took apart my calculator. It had 2 LEDs in it! So, when I got home, I took them out, and it still works fine! Just earlier today, I accumulated another calculator that I was supposed to give someone who I didn't even know. I took it home, and took the LEDs out of it, and IT still works fine!

The calculators I got these LEDs from are called 'Texas Instruments' just for those who wanted to know.

Anyways, they are nice, small LEDs, and would be PERFECT for underglow lights on a bit. Just thought I'd take a couple pics of em too, just for good measure :D

The second:

A little side note:

If you do this to your calculator, and it doesn't work, it's ok! Where you unsoldered your LEDs, those two contacts should get soldered together. If it still doesn't work, just unsolder one of the two, and if it still doesn't work, resolder the one you just unsoldered, and unsolder the other one. If you need more help, I can take some pics.

Saying that its a Texas Instruments calculator only narrows it down to about 100. Might wanna include the number on the front. FOr example, my graphing Calculator is Texas Instruments TI-83Plus.

~Mike

The one that I recently took em out of was a TI-30, and I think mine was in the 20's.

I've noticed that the TI-32's have leds too. I wonder what they're for?

Well, to me, they are absolutely useless. You can't see them or nothing, so I took mine out, and my calculator still works fine.

Maybe they ran out of regular diodes.

Lol, I doubt that one :p

so do they light up? what color do the clear ones glow?

They work, but They don't light up in the calculator, I tried all the buttons, but nothing happened. They all go red. Even the clear ones.

Use SMT led's to make under car lights. . .

The LED's inside the case that aren't visible from the outside probably help the manufacturers to test the calculators in the factory before the case goes on. The board, before it even gets its buttons and screen probebly passes by a person on the assembly line and they look to see if it blinking or it might even blink a certain pattern. If its not, then the board gets scrapped. After the testing process is complete, the part of the circuit that makes the led's blink for testing is disabled. Led's dont cost very much so they just leave em in there.

Thats my guess....

~Mike

Geeze. . .thats quite a long train of thought there. . . i wouldnt have wasted my time on that i would think of what to do next to my bit

i have to agree with mikey. that is probably how they make sure they work. and that was very well thought out.

Led used as regulator in calc's
 

I took apart a bunch of old calculators and found that the LED's are actually working as a cheap power regulator. Usually found in solar / dual power calculators to keep the voltage limited to about 1.5-1.6v (that's where a red led begins to operate).

On one solar calculator, I took out the led, and the display would show all 8's! Every display segment lit up when I got close to strong light source or sunlight. Without the led the thing gets overvoltage from the solar panel and goes nuts!

Most solar calculators have a panel with 4 or 5 segments, and each one of those segments gives about 0.5v (with full sunlight), so what the manufacturers do to make these things run even with low light sources, is to put more solar segments than needed

The 5 segment panel can reach up to 2.5v with full sunlight (and the led is there to keep the calculator from getting any more than 1.5-1.6v

I found that putting black tape over half the solar panel would make it work like it still had the led in it. (leaving about 3 segments uncovered, for 1.4-1.5v in bright light)

i paid i believe like $5 at allelectronics.com ( i think) about half a year ago and got like half a pound of leds, i had (and probably still have) about 60 of those styl leds in 4 different colors.