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I have a possible plan and would like to know if its feasible,

Background
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at work i have access to about 20, scuffed and knocked about motorola talkabout walkie talkies.  Most of them have a broken send button, but it can be easily fixed, and the ones i have fixed send and receive okay out to about 1.5km, so i can assume they are ok.

objective
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not wanting to throw them out, i want to find some cool ways of putting them to use,

plan
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I have already made one of them into a crude perimeter monitor with a trip wire activating the call function to alert anyone on the same channel, I plan to put an arduino into the mix with a Laser and photo cell to make the trip wire a bit cooler.

BUT
this way i can only use one walkie talkie to monitor one location, at least if i want to know which location detects movement
QUESTION
does anyone know if it is possible to connect an arduino onto the mic and send tabs on the walkie PCB and send some crude data stream to the receiving walkie, which in turn with an arduino could be set to print the data stream to an LCD and reset the trigger on the monitoring system.
IMPLEMENTATION
a series of short timed puleses could be used as identifiers for the unit that has detected an event etc. or different tones could be generated etc. (i have looked into using resistors to match the arduino pin out impedance to the original mic impedance)

WHY?
i think it would be quite cool, plus it might help out with future zombie epidemics.
i also have some old digital cameras with broken screens lying around, and would integrate them to take photos of who passes, or use it as a deer cam that lets you know where the deer it traveling in real time,

i think its a worthy project


thanks in advance for any help
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You may want to check and see if those radios will require a license to legally operate, and if they can legally be used for data transmissions.
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im not sure about the data transmition, but the radios are licence free
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i found this

https://sites.google.com/site/ki4mcw/Home/arduino-tnc

its not exactly what i want to do because it seems to involve a pc at each end and use the arduino just as the modem,

any ideas, help ?
im starting to think its too ambitious but i have lots of walkie talkies i want to use
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well plan c

http://liudr.wordpress.com/libraries/phi_morse/

send simple morse code and have it printed on the screen, should do what i want and seems a lot mroe likel than a full blown modem being created by me, hahaha

still any ideas are welcome
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okay
this is the code i intend to go with,


http://code.google.com/p/morse-endecoder/

it is capable of watching a serial line and encoding into morse then sending it to another unit which decodes it from morse to text which it prints to serial output,

im assuming that instead of serial.print i can use lcd.print and instead of sending a character received over serial it can send a preset message when the external event becomes true,

thats the plan of attack,
ive noticed so many thread asking about help with audio over radio waves and no one helps, is it because its hard to do? or is it a bit of a taboo ?

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Quote
im assuming that instead of serial.print i can use lcd.print
No.

Quote
ive noticed so many thread asking about help with audio over radio waves and no one helps, is it because its hard to do? or is it a bit of a taboo ?
Basically because it is illegal. Many people think that just because a band is license free they can make something that transmits in that band. This is not true.

The same goes for your project. The license it uses does not permit mores code to be sent. However, I think there is little danger of you actually getting it working.
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grumpy mike

although a characteristically grumpy reply, thanks for making it anyway,

i agree that there is little danger of me making it work , but given your optimism on the subject i shall proudly let you know if i prove you wrong.

plus i will look into sending morse code over cb channels, i cant think its illegal, when i was a kid there was a morse beeper button on the walkie talkies,
unless the law distinguishes between a device transmitting and a human transmitting, we shall see

thanks,
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Quote
im assuming that instead of serial.print i can use lcd.print
No.


well , lcd.print is working just fine, sending the word out to serial and out to the lcd, unless there is something unforseen im guessing its going to work ,

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well grumpy

i have succesfully coded it to print out to lcd, to move the cursor for each new letter, to drop to the second line when the first is full,
and overwrite the top line when the second is full .

i have also programmed it to recognise certain text and print a different message to the lcd when that text is sent,
so all thats really needed now is to put it onto a radio and see if it transmits , if it transmits then i beleive bob is my uncle

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if it transmits then i beleive bob is my uncle

It'll be a good start, for sure, but I think you also need to prove the ability to receive and decode the signal before you can claim full brownie points. Good luck!
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if it transmits then i beleive bob is my uncle

It'll be a good start, for sure, but I think you also need to prove the ability to receive and decode the signal before you can claim full brownie points. Good luck!

I agree, but the guy who wrote the original code for serial communication , used mics and speakers for transmition and receipt, so as long as the radio side of that doesnt confuse it because of differing frequncies or interference then i think it will work off the bat,

i will tinker a bit more this afternoon and see what happens,
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well
a little update,
I have made an impedance load for the output of the arduino , i cant remember the resistor values now, but something like 300 ohm and 3kohm , that seems to work well,
Using tone() and noTone() at the right places in the code i have acheived the buzzer accoridng to the morse output,

Then with the resistors on the output i piped it into the mic in on the walkie, and my morse comes out of the RX while being printed on the TX lcd,

So now i have to build the circuit again for the Rx and see if it prints what i receives,

then for text recognition i guess i have to start storing the idividual letters transmitted into a string and compare that string to preset values right ?

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Sounds like you are essentially just making an old-fashioned modem, we did that sort of thing in the 80s, IIRC we used DTMF en/decoder chips. Maybe they would work for you.

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Sounds like you are essentially just making an old-fashioned modem, we did that sort of thing in the 80s, IIRC we used DTMF en/decoder chips. Maybe they would work for you.

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Rob

rob,
the general plan is to have fun resuing old crap from a parts box. but i am trying to make essentially a basic radio modem , would the idea of the dtmf chip to be to make it transmit certain tones and the other end decode them ? and then use the arduino to act accordingly ?

i am not very good at electronics, so anything more complicated than breadboarding an arduino and basic stuff is beyond me for now, although i can happily surface solder that doesnt neccesarily mean i know what im soldering smiley
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