Instructables

Arduino text'in

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Picture of Arduino text'in
Arduino text‘in.

Key Features:
24 relays controlled by 4 I/O lines!
Cell phone text using your Arduino.

This project hacks a cell phone to text using normally open relays. After investigating cellular modules on the internet I decided it looks not only rather pricy, but also like a possibility that even after I had it working that a cellular provider might not let me put the device on their network. It seemed like a good cell phone hack was in order to make this work for me.
 
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Step 1:

Picture of
Phone screws 1.JPG
Purchase a cheap prepaid flip phone, activate and charge it. Mine was $20.00.

Flip phones are fairly easy to disassemble. You will need a very small screw driver set. The button pads on the inside are still large enough to allow for soldering wires in place without too much trouble. The prepaid plans let you text for pretty cheap too if you pick the right plan. Plus because its prepaid you can just let it run out whenever you are finished with it and best of all no contract.

Turn on the flip phone and take some notes about how it operates. Yours may access menus and things differently then mine does and its nice to know as you move forward with this.

Figure out what keys you still want to have access to once the phone is mounted. Because I used a prepaid phone I have to access it now and then to add more air time. It is also helpful to know how things are going with the phone when you can turn it on and activate it with the buttons after it is mounted to the board. The buttons on your cell phone board will be connecting directly to the phone. This way you can access the phone even if the rest of the circuit is off or maybe just doing other things.

Safety First. Remove the battery from the phone. Tear apart the flip phone. The circuit board inside is pretty delicate and has some sharp parts so use some caution. Do not break the LCD displays and be very careful not to destroy the very small ribbon cables that interconnect things. The part of the phone that houses the LCD, microphone and usually the camera will need to be taken completely out of the case. The flip phone I purchased had enough room to flip the camera around so that it can still take pictures. The case for the main board of the phone (where the battery is) will need to stay more or less intact. This makes it easier to put the battery back in and your not messing with the built in antenna so it should still have its normal signal strength.
bearly1 year ago
Will you please specify what kind of Reed relays you're using. I don't have a bunch of those laying around and I could not find any details about which I need to purchase following your instructions.
Very valuable and inspiring instructable in many ways, you made.
ray74 (author)  bearly1 year ago
Any reed relay will do as long as you match the coil voltage requirements. You can get them at Radio shack, Jameco, Mouser etc. Mail order will probably be the cheaper route :)
Nice work.... Congratulations on a well deserved win! Maybe you can give me some pointers on the prize we won in the hackit contest... I have never heard of these things before!
poofrabbit1 year ago
Hey congratulations on being a finalist in the hack it contest! Good luck to you!
ray74 (author)  poofrabbit1 year ago
Thank you poofrabbit :)
Roger_M1 year ago
As each serial data stream is clocked in to the shift registers in real time each output will change state with the current clock pulse in accordance with the current state of the bit stream. It is only the fact that the data stream is loaded much faster than the relays can respond (several ms) which stops ALL the relays changing state as the bit stream data is clocked in. This could be prevented if the drivers to the relays were inhibited starting at the start of the first clock and uninhibited just after the last clock. A mono triggered by the first clock edge with a period exceding the time taken for 24 clock periods could be used.
ray74 (author)  Roger_M1 year ago
That is correct Roger_M.
This same technique also works with lcd displays. Shift registers are amazing :)
brenryan1 year ago
Great work! Really cool. Can you please please post a video if possible? I love the sound of relays, I would say it is most satisfying to hear them clacking away whilst it types a message :)
ray74 (author)  brenryan1 year ago
Thank you brenryan.
I will see what I can do about a video. I agree with you about the sound of relays. I used reed relays in this so they are really quiet. I did turn the sound on for the button activation on the phone and that is still very satisfying.
samaddon1 year ago
purely genius! but it requires a lot of hard work and that's not possible for a child! great work ! i can't get words for your creation!
ray74 (author)  samaddon1 year ago
Thank you samaddon. Though this project does require a bit of work. I think that you can do anything you set your mind to. :)
samaddon ray741 year ago
Hey! ray!
do the instructables gave you the pro membership as a gift for this great instructable?? cause i got for three months a promembership gift for my which is How to make a soldering iron with a 6 volts battery you can search it's featured!
ray74 (author)  samaddon1 year ago
Hi samaddon
Your instructable "How to make a soldering iron with a 6 volt battery" is very creative. I am amazed every day at how creative people can be. It had never occurred to me before looking at your project to try to make my own solder iron. Thank you for sharing your talent.
samaddon ray741 year ago
Hey! ray!
do the instructables gave you the pro membership as a gift for this great instructable?? cause i got for three months a promembership gift for my which is How to make a soldering iron with a 6 volts battery you can search it's featured!
Amazing project ...very nice code layout too!
Build_it_Bob
ray74 (author)  Build_it_Bob1 year ago
Thank you Bob.
askjerry1 year ago
Most cell phones, and electronics in general for that matter ground the pin to act as a keypress. So instead of using ($) relays you could use a transistor like this... http://www.digikey.com/product-detail/en/2N5210BU/2N5210-ND/1422

You can get 25 for $4... probably less than 2 relays. You are already using a transistor to drive a relay... see if you can drive the switch directly.

If that doesn't work you can look at something like this...
http://www.digikey.com/product-detail/en/CPC1972G/CLA224-ND/1025050

Then you won't need the transistor and relay... the device will do both making your circuit simpler. Here is the datasheet
http://www.clare.com/home/pdfs.nsf/0/E16FD7FE1462A2DD852570F800586DFD/$file/CPC1972.pdf

Just need a dropping resistor for the input... but that's pretty simple.

Jerry

ray74 (author)  askjerry1 year ago
Thank you Jerry. I will check it out and let you know how it goes.
not really ... my experiments told me that they are using cross matrix key pads. Therefore I used cmos switches to implement a "remote keyboard"
http://www.instructables.com/id/Samsung-MOD-fixed-...-mobile-...-TV/
starlino1 year ago
If you ever revise the design consider using digital switches instead of relays. Great work.
ray74 (author)  starlino1 year ago
I have not tried digital switches yet. Thank you.
This is epic &I admire your technique. Another good reason to keep old cell phones!
ray74 (author)  moebuspcgold1 year ago
Thank you. I enjoy taking them apart. :)
jolshefsky1 year ago
This is a really (relay, ha) cool idea. I too have seen the allure of cell phone modules, but it's more likely I'd want something cheap that I can guarantee will be permitted on a prepaid network.

You may be able to simplify your circuitry a lot. The keypad probably uses the ever-common "pull high, connect to ground" model of switches (that is, one side of each button is tied to an input pin somewhere and a high resistance pulls it to +V and the other side is connected to ground so when the button is pushed, the input sees 0V, otherwise +V.) If that's the case, you can then go with one wire to each button pad and one wire to a common ground. Also, since your phone is isolated from your Arduino, you can then just use an NPN transistor with the collector connected to the button pad and the emitter to the common ground which you'd then tie to the Arduino's ground. The transistor driver for the relay can then be used without the relay. I hope that's clear enough!
ray74 (author)  jolshefsky1 year ago
Thank you. And thanks for the advice.
agis681 year ago
this job is epic and chaotic on my eyes. You could had the same extact result using a nano duino or even if you the atmgega chip and then only the complete cellphone without be in so much trouble to transfer the keypad and screen on a prototype board. Connected by a cheap shield on the phone and all are ok....ofcourse the code remains. Tell me please why someone do all this trouble....the only anser for me is only to get more knowledge and some experience....but if you are so good with arduino there's no need all this. Simplicity my friend is the first rule of a scientist
paqrat1 year ago
Perhaps it is because I have little knowledge of electronics but I fail to see what this is for. You appear to have put much time and thought into it and it may be the greatest thing since sliced bread but I have not been able to decipher what its function is. What does this do? How would one use it? Why would I want to go to what was apparently a lot of labor to make these modifications?
Ummm... Couldn't you simply send AT commands to your cell phone using arduino? You can possibly do all you wanted to do here. And your phone would remain intact.
it works for some phones using AT-commands only. I did that with an old Siemens phone, that I connected to my Linux server.
http://www.instructables.com/id/The-S45-SMS-Alarming-System/
I am not shure how this works with Samsung phones. But I belive that it is possible, ate least using properitary AT codes of the manufacturer.
There I found an old manual of a device I also used for receiving and sending SMS messages with a computer.
http://www.falcom.de/uploads/media/a2dman.pdf
Maybe theses AT-commands work for other devices too ...
AndyPipkin1 year ago
Couldn't you use the Arduino to write AT commands to the phone as a modem, to send SMS?
james.m.k1 year ago
OK, are you saying that you can use these "Open Relays" at no cost other than keeping your phone active? Otherwise what's the point?

I, for instance, use TracFone, and get charged for every single message I send or receive. Though I do still have an older phone that gave me free messaging.

What would be REALLY neat would be if you could mount it all in a case small enough to fit in your pocket!

What would be the ultimate in cool is if you could still use it for sending and receiving calls. Then you wouldn't be forced to carry two phones, one for texting, and one for calls.
florinc1 year ago
A much easier and cheaper solution is using a GPRS shield, like this one
http://www.seeedstudio.com/depot/gprs-shield-p-779.html?cPath=132_134
with an Arduino.
I don't understand what this is doing. Is it using the arduino to act as a keyboard, taking it's input from the switches & using the relays to "Push" the same key on the phone ????
ray74 (author)  Lectric Wizard1 year ago
Hello Lectric Wizard,
The relays are controlled by the Arduino that is running the program. The Arduino doesn't actually monitor the buttons. The buttons are there so you may interface to the phone should you need to.
Thank you for the question.
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