wireless sending

[ed1380]

so i got me a ti 83+

it has a link cable so you can connect them, and there are programs out there so you can chat.

what I want to do is make it wireless   for reason i'll keep to myself

I've thought of using the xbee or w/e it's called, but that's to expensive to be practical, so I'm gonna use IR.

what kind of range could I get with it?

here is what ive found so far http://sami.ticalc.org/irlink/e_intro.htm and http://www.michaelv.org/programs/calcs/calc_mods.php

first source uses a PIC on each side to transmit code

second one connects IR reciever directly to calculator.

since there is the whole rx, tx thing, how would you guy thik this would work out?

[Rebelgium]

Well, you are obviously looking for a way to cheat on tests.
Don't you think the teacher will see the piece of PCB hanging out of your calc?

[airman00]

not if he hides it within the calculator   

[Rebelgium]

That's not going to be easy, there's no place for it... (I have a TI 84plus)

[paulstreats]

If it already has the ability for a link cable, maybe you can just use a serial radio chip

[ed1380]

not cheating. I got a 96.6 in math

 just chatting in class since the teacher don't care what we're doing as long as we're quiet

i'm not planning on putting it inside. just gonna be a little pcb or something that the cable plugs into.

I'll look into that paul. any hints on how to find it?

so any other advice to my questions?

[Admin]

you forgot to do a google image search for IR transmitter circuit

The simplest circuit would be just an IR LED and transistor for the transmitter, and an IR transistor and op-amp for the reciever. This will give you a few inches, maybe a foot or two.

But to get better range, you'll have to do more complicated modulation. Maybe hack a tv remote control.

[ed1380]

i got teh circuit. but this modulation that you speak of. what is it?

for longer range I was thinking of using a laser and photocell.

lucky me has a tv that i hacked some time ago

[airman00]

modulation is the process of varying a periodic waveform, i.e. a tone, in order to use that signal to convey a message

Modulation is used in TV remotes.  how does a tv "know" that you pressed #2?  By the remote modulating the signal according to the button and the tv deciphering this message.

[Admin]

but this modulation that you speak of. what is it?

airman00, thats a different modulation. Thats just a lamen's way of saying a square wave (sending binary).

The modulation I'm talking about is:
take sensor reading with IR xmitter off
take sensor reading with IR xmitter on
subtract both values (thereby eliminating environmental noise)

this is really tricky to do when you are also trying to send data, and not just do line following or range finding . . . and I've never done it myself . . .

I think the TV remotes do this, so if you can hack it to figure it out, it would save you time/effort. You just need to find the tx/rx pins in the remote and in the TV and you are done.

[airman00]

The modulation I'm talking about is:
take sensor reading with IR xmitter off
take sensor reading with IR xmitter on
subtract both values (thereby eliminating environmental noise)

i never thought of that admin!

I'll add that into my code for the line follower robot.

[ed1380]

wouldnt the calculator automatically be doing this when sending data?

I'm trying to find out now how fast can a phototransistor switch on-off.
if IR can only do a few feet then I might have to do the flashing laser

[Admin]

I'm trying to find out now how fast can a phototransistor switch on-off.

its in the datasheet of the phototransister. look for a square wave timing chart in it. some small time, like a few microseconds probably.

[Rebelgium]

Using a laser won't be a good solution.
You'll have to point the laser exactly at the receiver...

[ed1380]

i know.

but would it work? would all teh modulation and baud and whatnot line up? (I'm a noob at that)

[dunk]

I'm trying to find out now how fast can a phototransistor switch on-off.

TV remote receivers (ie, the circuit in the TV) use a little package containing an IR phototransistor and circuitry to filter out 38kHz carrier signal.
the TSOP1738 is an example of such a device although there are others.
most of these devices don't need an exact 38kHz signal. they will still trigger if your timing is out by 5% or so.

to create the 38kHz signal in the first place you can use a NE555 or similar set up to run at 38Khz and connect the 555's enable pin to your transmitting device's TX line.

on the TSOP1738 connect the Data pin to your receiving device's RX line.

dunk.

[fr4ncium]

Hahaha I always wanted to do this in high school too!  Math class was soooo boring and that was when I really got into programming.  I wrote a calendar organizer program for my 83!  I had to be a little creative with text entry though, as there is not way to store it - so when you selected the day on the calendar that it drew, it would interrupt the program, and when you choose to "goto" the error line, it went to the line that stored the String output for that day's tasks.  good times.

[HDL_CinC_Dragon]

I recently found out how to store string variables and matrix data to my calculators memory so when I turn it off, the data is still there My calc is a TI-84+ Silver Edition. Love it Ive written some really fun and interesting programs on it. Including one that kind of resembles the "Beziars" screen saver of windows 95' or 98' a little bit. Forget which one though

[Admin]

I used my TI-89 every day in college . . . but as soon as I graduated I found it utterly useless.

A combination of being able to do the math in my head, and having complete access to a PC and the internet to solve problems did it in . . .

[ed1380]

I'm about to order the ttl-232 converter and gps antenna from sparkfun

what could I also get form there to save on shipping? something cheap and maybe useful that i didn't happen to see