TI-83 Plus Silver Edition LED Mod

[harding802]

Hey, I just got a new TI-83 Plus SIlver Edition.
http://education.ti.com/images/product/tech/83pse/83PSEbig.JPG

I can not read the keys or the display in the dark, imagine that. So, I had this idea.

Why not do this. Get some of the tiny LED's and put them throughout the calculator where the keys are, not on the bottom. these would be on all the time. on the other side (the back) i would put 4-6 flashing LED's just to annoy someone when we are using the DLP in class :)

Then, get four more of the tiny ones and have them put on the sides of the screen so you can read that in the dark as well.

total of say 10 TINY LED's on the front, 4-6 tiny leds on the back and then say 4 (white?) led's on the screen, but under the plastic so that you don't have anythign sticking out.

(sounds like a DBvader project for some reason...)

Anyway, think this will work? There is so much open space in teh calculator, that will CERTAINLY not be an issue.

My only worry is that NO ONE on the net has done this, not to any calculator that I have seen... SO I was thinking... anyone know of a site? Think it will work? Any tips? Know of a forum where they do this stuff? PC Mods.com has no forum...

Thanks for the input!

[Adisharr]

Hey that's a great idea :) A few possible problems..

1. Illuminating the keys from below if they are not made from a translucent plastic. You don't want light shining in your face - that would make things even worse.

2. Power draw from the LED's may overwhelm the batteries. You'll need some very efficient LED's.. Consider 2mA units and below.

You may have to build a small ttansparent riser around the sides of the keys and embed the LED's in that to get the desired illumination.

Let me know if you decide to do it.. ;)

[harding802]

it is hard to see from that picture, but everything about the calculator is translucent, infact... le tme see if i scan it that maybe you can see better...http://www.soundwise.org/klipschubb/ti-83.jpg

well, kinda helps. even the 'black' keys are translucent

there is enough room in the back for 4 more AAA batteries JUST for the LED's.

i am trying to get some place to get the LED's locally, Fry's and Radio Shack are my best bets. hopefully they will have what i need, thoughthe lowerst poewr i have seen was 10mA

[dighn]

try some real electronics components sellers. if you have trouble finding them locally, you can trywww.allelectronics.com or www.digikey.com.

[Adisharr]

That's good news the keys are the right kind.. keep in mind that you can power the LED's below their rated operation current and still get a ton of usable light. I have some small 2mA units I run a 800uA with just about the same intensity..

If you can, try and get a sample of each and try them out with a variable resistor..

[harding802]

it can hold 6AAA's, there is that much extra room :) Yeah.

so, i will get the lowest amp lights i can find, since i don't want to have to wait for anything, or blow up half of them and have a halfway job for two weeks :), i am just gonna use fry's or radio shack, they have a pretty good variety.

here is my idea, i will find a pretty thin board with the pin holes in it. use that to hold the lights and cut the board to make strips so everything is uniform and all.

my question...
i have done lots of LED projects and currents etc, but i ALWAYS get my series circuits and what not mixed up.

lets say all the lights are exactly the same, and i am using 4 AAA batteries to power it (or two 9V batteries). one resistor or two? one for positive and one for negative, i really just need a site. used to be a place called like LED Fun where this guy had anything and everything you would ever want to know about LED's and modding things with them.

anyway, any tips would be great!

trying to think of a way to light the screen, the most important thing to light really since it needs it the most (does not reflect what light i have in the room like the buttons do). this was my idea on that.

get a thin piece of glass, only as thick as the LED (hopefully a micro LED) anyway, some how implant two LED's on each far end (left and right) of the glass. (if i put it on the left and right the actual lights will not interfer with the screen for about 3-4mm.) the LED's will light the glass which will light the screen, like those glass plates you put on books to light it without getting light on your eyes, they sell them at barnes and noble for $20-40.
course, it seems like they may have the bottom end of the glass microscopically etched to let the light out... over my head there :)

any ideas welcome!

[Adisharr]

Originally posted by harding802


lets say all the lights are exactly the same, and i am using 4 AAA batteries to power it (or two 9V batteries). one resistor or two? one for positive and one for negative, i really just need a site. used to be a place called like LED Fun where this guy had anything and everything you would ever want to know about LED's and modding things with them.

trying to think of a way to light the screen, the most important thing to light really since it needs it the most (does not reflect what light i have in the room like the buttons do). this was my idea on that.

get a thin piece of glass, only as thick as the LED (hopefully a micro LED) anyway, some how implant two LED's on each far end (left and right) of the glass. (if i put it on the left and right the actual lights will not interfer with the screen for about 3-4mm.) the LED's will light the glass which will light the screen, like those glass plates you put on books to light it without getting light on your eyes, they sell them at barnes and noble for $20-40.
course, it seems like they may have the bottom end of the glass microscopically etched to let the light out... over my head there :)

any ideas welcome!

As far as LED wiring goes.. Keep in mind the following..

Every LED has a voltage drop across it in a circuit. It's LED dependant but it varies widely.

If you put LED's in series you need to add all these voltage drops together. Say each LED drops 2V. You put six in series (+ to - to + to - etc..) and you have a voltage drop of 12V. That's more than your AAA batteries can put out.

Two 9V batteries can power a circuit like that. Putting the batteries in series give you about 18V. You take the LED voltage drops from that and you get 6V left. If you just hook the battery to the LED's w/o a resistor to limit the current they will probably burn out. Essentially you have a short.

Next you need to know how much current the LED needs to light up properly. Say 10mA or .010A for example. You now have a circuit with a 6V source and you want to limit it to 10mA.

R = V / I

Resistance = Voltage / Current

R = 6 / .010

R = 600 ohms

+V----------/\/\/\/---------LED--LED--LED--LED--LED--LED-----Ground

The +V is the battery +
\/\/\/ = 600 ohm resistor
Ground = battery -

The LEDs anode (+) should be attached to the positive side of the battery. It doesn't matter where the resistor is in the chain as long as it is in SERIES. 10mA of current will flow through each LED.

Now consider a different way of doing the same thing. A PARALLEL circuit..

+V----/\/\/\/--------LED----!-----Ground
!---LED----!
!---LED----!
!---LED----!
!---LED----!
!---LED----!

Say you are still using the 18V source and the LEDs are same as before (2V drop and need 10mA each). Since the LEDs are in parallel now the voltage drop is not added. The total voltage drop is now just 2V. That leaves you will (18-2) 16V to work with. Each LED still needs 10mA but because they are in parallel you will need to supply the circuit with (6x10mA) 60mA for them to light properly.

We can now figure out R...

R = V / I

R = 16 / .060

R = 266 ohms

There is a catch, if you try to run too many LEDs this way you may exceed the power dissipation of the limiting resistor. You can figure out how much power you'll be dissipating by using the formula....

Power = Current(squared) x R

P = I^2 R

60 mA flowing through resistor, 266 ohm resistor

P = (.06)^2 (266)

P = (.0036) (266)

P = .95 watts

Most small resisotrs are rated at .25 W so that won't work. Higher power resistor are much larger but you may be able to fit them in ok. Another solution is to give each LED it's own resistor..

+V---------------!--/\/\/\---LED----!-----Ground
!--/\/\/\---LED----!
!--/\/\/\---LED----!
!--/\/\/\---LED----!
!--/\/\/\---LED----!
!--/\/\/\---LED----!

In this configuration you can treat this circuit like it was just one LED and one resistor..

+V------------------/\/\/\---LED----------Ground

Source Voltage - LED voltage drop = available voltage

18V - 2V = 16V

LED needs 10mA or .010A

R = V / I or 16 / .010 or 1.6k ohm

P = I^2R

P = (.010)^2 (1600)

P = .16W (more reasonable for a small resistor)

Keep in mind that each LED you add to the parallel branch will need 10mA more from the power supply.

In the case of the batteries their energy supply will be rated in mAH or milliamp hours..

Say for kicks..

500mAH

That means it can supply 500mA for a period of 1 hour

So...

If you have 6 LEDs drawing 10mA each (60mA) you can run that circuit for (500/60) 8.33 hours

Hope this all helps a bit I'm starting to put myself asleep :p
P.S. If anyone notices any screw ups please tell me and I'll fix it :)

[harding802]

You are great, brought everything from last years physics back, and then some :)

i was thining a parallel circuit also. space is the only issue with that. i will open it up and get a pic or two of the inerds space so you guys can get an idea, if you have another. as far as a power supply. i wonder if there are any rechargeable NiCD or NiMH batteries that are thing and would work in this, just to save money on the lights. but when you think about it... The lights won't be on all the time, certainly not all the time that the calculator is being used. only really when the lights are off, say 20 minutes a day max. and then occasionaly to show off how cool i am hehe :cool:

gonna print this out and make a trip to Fry's perhaps

Thanks again

anyone else, please speak up if you like :)

[Adisharr]

Originally posted by harding802
You are great, brought everything from last years physics back, and then some :)



hehe Thanks man.. I'm glad it's of use to you.. I wouldn't say priceless.. maybe $ 2-3 but that might be overkill :p

Definately post pics if you can.. would be cool to see the innards ;)

[urashima]

how sad.. i did the same thing. here's what i did however

------------- <<<-- that is the glass layer of calc
XXXXXXXXXXXXX <<<-- i put a thin piece of fiberglass
_____________ <<<-- this is the circuit board

i used yellow and green leds (school colors lol) and it kinda looks like the retro 4AA game boy... other than that it's really cool!

[mrspm2003]

Hmm this is a good idea indeed..but... why would you need to use the calc in the dark? I mean if you use it, your prob doing some kind of problem, in which you need light to work some of it on paper... which means you really wouldn't need a LED mod..but I don't know, I just bought a Ti-89 calc..and sounds like a good idea to mod. Let us knows how it goes!

[DiZzZzY]

you can use the lights because some people use graphing calculators to play games. On the Ti-89 you can even play some 3d games. So you wouldn't always need the light for a problem.

[harding802]

I need it for the overhead projector, when we use that, or the DLP, I can not read the calculator. i am putting white led's on the bottom so it will shine on my desk just enough to light up the paper :)

my school colors are blue and white, the most expensive LEDS... haha (well, maybe not THE most expensive... but certainly not red or green:D)

i had an idea!

What about adding the batter and power supply of one of my many extra Cybikos. they use NiCD batteries and I could drill a tiny hole into the calculator to connect the power supply so i could just recharge! what do you think about that?

[harding802]

oh yeah, urashima, were you lighting up the screen? got any pics? :)

[harding802]

May have to put this on hold... I just bought some Sennheiser HD600's and am about to venture into building this beauty...

my HD600's just don't cut it when I use the ChuMoy amp i built. So, eat your heart out! :)


http://64.124.101.64/amp_img/cover_shot.jpg

http://64.124.101.64/amp_img/front.jpg

http://64.124.101.64/amp_img/back.jpg

http://64.124.101.64/amp_img/inside.jpg

notice the headphones? None other than some HD600's! :)

What's inside the amp

- Handmatched Vishay-Dale resistors, matched to 0.05%
- Transistors/LEDs matched to 0.05%
- OPA227 opamp for servo loop
- Alps Blue potentiometer
- Neutrik locking jack, black w/ gold contact
- Cardas RCA jacks
- XLR connection between PS and amp
- Ultra-bright blue LEDs

What is in the power supply:

- Talema toroidal transformer
- Panasonic caps
- Wima box caps
- Vishay-Dale resistors matched to 0.05%
- Adjustable voltage output w/ pot, 5V to 24V 800mA