Home     Contact     Projects     Experiments     Circuits     Theory     BLOG     PIC Tutorials     Time for Science     RSS     Terms of services     Privacy policy  
 Home      Projects     Experiments     Circuits     Theory     BLOG     PIC Tutorials     Time for Science   

This project is not completed yet - Last update: October 22, 2012
GSM Caller AlarmAuthor
Panagiotis Kalogeris
October 1, 2012

Do you have a cell phone laying to your drawer and you want to throw it away because you think it's useless to you??? WELL DONT!!!
In this project i will present you a really simple GSM CALLER ALARM.
This project can be very handy,since you can have call notification to your phone or your cell phone when the application that was installed to triggered the input of the GSM CALLER ALARM and made the call to you.
It is a very cheap solution because the complete project cost me 6 euros including the box and in addition to the simplicity of the circuit makes it an affordable and easy building constructional project.

Circuit in stand-by mode. Just activated... Making a call!!!

Circuit Overview

As i said above the circuit is really simple.The heart of the circuit is a pic microcontroller 12f675 which does all the job in corporation with a quad cmos bilateral switch (cd4066) for the interface with the cell phone.
The cd4066 acts like our fingers when we press a button.
So when the input of the pic has been triggered, the pic sets high one output to activate the cell phone.
Then with an appropriate delay ,the pic gives time to the cell phone start-up and then again the pic activates the second output to accomplish a "Fast call".
Apart these two Ic's pull down resistors are placed to the inputs of the cd4066.Also i have used a pinout header to the input of the pic so you will have the option to change the polarity of the input according to your needs.
(Except hardware,software changes must be made.Further info below...)

The schematic

In my schematic you will notice that i have used a ceramic resonator instead of the internal oscillator of the pic.And that's because i accidentally erased the internal osccal value of the pic... :-( .If you use pickit programmer (I use pickit3) there is an option box in the settings tab of MPLAB where you can tick it in order to prevent osccal overwriting.There is a good explainatory article in Peter's site where he says how you can recalibrate the factory osccal value.... Here.


Well i think its now time to calibrate the circuit according to our needs.
The first parameter to the calibration procedure is to see what polarity output has the application that is going to be placed.For example...
If the output of the "alarm" is negative,then you must place the jumper between common and +5 pins.
If the output of the "alarm" is positive then you must place the jumper between common and GND pins.
Thats for the Hardware.
Now as for the software you must locate the instruction BTFSC GPIO,3 and change the last letter from
C to S........BTFSS -> for those who expect positive input.
S to C........BTFSC -> for those who expect negative input.
The second parameter is the delays...
I have used an old Alcatel OT-209 cell phone.So the delays in my programm is according to this cell phone.
If you possess a different phone,Then you will have to make a test first to see how much time is needed
to start-up, to locate a network and finally how much time is needed for a key to be pressed to achive a "Fast call".
When you will have done the test, you will have the time for each step that the cell phone needs.
In my programms i use comments.... Search for the three instruction lines:

call wait1sec ;start-up phone
call wait15sec ;delay until network ready
call wait2sec ;fast call

Τhen you can simply change the the number of call Wait1Sec instruction between 1 to 20 (reffering to seconds).


Coming soon...

Conclusion - Considerations

At last there is another thing that we didn't discuss...I will use this project to my car.
Since that i didn't want to have the battery installed to it ,because i have seen batteries exploding due to material failure or perhaps to wrong charging method etc...
In order to avoid this unpleasant surprises i decided to remove the battery from the phone.So as you will see to my schematic i have used an LM317 to supply 4V to my cell phone.
If your phone's battery has different output voltage, then you must change the 2 resistors according to this formula
VOUT= 1.25V(1+ R4/R5)+IADJ(R4)
or if you are bored of making calculations you can use an online calulator Here
Also i must admit that this project is not the best, since there are GSM MODULES where you can control them thru AT Commands and in a very low prices.
Perhaps a new version of GSM CALLER ALARM may come to the future...

GSM Caller Alarm Firmware

The firmware Programm available for downloading.I have included the whole microchip project where you can easily modified it to your needs...

Download file
GSM Caller Alarm software V1.0 (Including Microchip Project)



  Email (shall not be published)


Notify me of new posts via email

Write your comments below:
BEFORE you post a comment:You are welcome to comment for corrections and suggestions on this page. But if you have questions please use the forum instead to post it. Thank you.


  • At 23 September 2013, 23:26:51 user Jon wrote:   [reply @ Jon]
    • @Panagiotis Kalogeris -- Hi Sir, please email me as I'm interested in hiring you regarding PIC design. Thank you.

      Jon S. K.

      My email: jonthesleuth@yahoo.com

  • At 27 October 2012, 22:49:22 user Panagiotis Kalogeris wrote:   [reply @ Panagiotis Kalogeris]
    • And i was about to post the video and the code..... Ok i'll try it and i will tell you the results.

  • At 27 October 2012, 16:38:26 user Giorgos Lazaridis wrote:   [reply @ Giorgos Lazaridis]
    • I am not sure but i think that the error if you delete the osccal is not significant, especially if you want low accuracy. You could for example flash an LED at 1sec interval and count it over 30 seconds and recalibrate osccal. Is it possible for you to test the error with the internal clock? It would be a nice experiment for all!

    reddit this Reddit this

     HOT in heaven!

    NEW in heaven!

    New Theory: AC electric motor working principle

     Contact     Forum     Projects     Experiments     Circuits     Theory     BLOG     PIC Tutorials     Time for Science     RSS   

    Site design: Giorgos Lazaridis
    © Copyright 2008
    Please read the Terms of services and the Privacy policy