Mobile Phone Alarm for a Motorbike, Car or Anything You Want




I got fed up with normal alarms making a lot of noise, and no one taking any notice of them any more.

Also not knowing if anyone had messed with my bike because I was to far away to hear the alarm.

So I decided to make this alarm using an old mobile phone and a simple timer circuit.

The basic principle is if the motorbike is moved it will trigger a timer circuit,
which will send a 3 second pulse to a mobile phone, which will phone me to let me know that something has moved my bike.

This project is not just for a motorbike, It could also be altered you warn you about anything you want.
ie house, shed, car.

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Step 1: Items Needed

1 old phone with speed dial.
1 mobile phone car charger.
1 555 timer chip
2 relays 12 volt
some tilt vibration switches.
some resistors and capacitors
some wire
a small plug and socket. (a phono plugs is ideal)
Some electrical tools and a little electronics knowledge.

Step 2: Modifiying the Phone

To start with I got hold of an old nokia mobile phone.
I removed the case and carefully removed the front panel that sits underneath the keypad. this was held in place by torx screws.

Then I wired two very fine wires to the button contacts under the digit (3) it doesnt mater to much which button you use but I used this number because its not used for my phone number and because it was close to the side of the phone so it was easier to bring the wires out.

When I had attached the 2 wires I then reassembled the phone and checked it worked ok. by shorting together the connector with a piece of wire. to make sure the phone will activate the digit 3.

Next you will have to go in to the phone menus and set up a speed dial on button 3 for your own mobile phone.

After I had done this I shorted the connector again to check the alarm phone will call my mobile.

Step 3: Timer Circuit

Next job was to make a simple 555 monostable timer circuit. You can find lots of useful information on building 555 timer circuits here.

the relay coil is wired between the 555 timer IC output and 0 volts.
you will need a diode across the relay to protect the timer chip.

The reason for the 555 timer circuit is to make sure when one of the sensors on the bike is triggered it will cause a 3 second signal that will trigger the phone.

It has to be 3 seconds other wise the phone will not dial the number.

I used a 13K resistor and a 220uF capacitor for R1 and C1 this gave me a 3.14 second pulse.
You may have to change the values slightly depending on the phone you use.

Step 4: Connecting It All Up

I then wired 2 wires from the relay contacts to a socket, and pluged the connector from the phone in to the socket wired to the relay contacts.

I was then able to check that the timer circuit will trigger the phone correctly.

The next job was to connect up all the sensors to the timer circuit.

This was just a matter of connecting some tilt switches and vibration switches in parallel to a relay. Which will trigger the timer circuit when movment is detected. They can be connected directly to the circuit with out a relay but I found using a relay gave me more options and a more positive switch.

You can have a many switches as you want.

In the past I have also wired my garage door in to the circuit.

Step 5: Fitting to the Motorbike

Then next job was to fit the timer circuit and relays in to a plastic box. And fit the parts on to my motor bike. And connect up the phone charger to the bikes ignition so when I am riding the bike the phone gets charged.

I had already fitted a bike immobiliser on the bike

so when the ignition is switched off the alarm is armed and when I reset the immobiliser, the power to the sensor / trigger relay is switch off. which will disable the alarm circuit.

I just wired the sensor / trigger relays 12v supply, from the immobilizer relay so when the immobilizers led is lit the alarm sensor relay in powered.

Step 6: Final Testing

after I had installed everything on the motorbike.
and wired everthing up.

It was just a simple job of trying to move the bike with the ignition off and seeing if the phone dialed my mobile.

if not you may have to make some fine adjustments to the movment and vibration switches.

you will be able to tell if they are activating the relay because you will hear it clicking on and off.

If the relay is being activated but the phone is not dialing you will have to check your wiring on the timer circuit.

and that is about it.

Step 7: Future Upgrades

Some future plans I have are.

modifiying the phone so that if anyone sets the alarm off. I can phone the bike back and set off an audiable alarm or siren.

Also to completly disable the bike to stop them being able to start it.

or even instead of a audiable alarm / siren I could have the bike broadcast a message like " please move away from this vehicle"

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    62 Discussions


    2 years ago

    could you broadcast a signal on an unused part of the FM band and have your phone tuned into the frequency for the signal of movment to avoid using a cell phone with a Sim card ?


    2 years ago

    Nice One!


    3 years ago

    I'm having a lot of problems with people getting in my car so if you could send me a detailed version that I could hook into my car schematic to wire into the car wiring like when someone opens the car door I would really appreciate it thanks you can send it to


    3 years ago

    Pls send me a schematic diagram


    3 years ago

    Dear Sir,

    Wow! This is nice project. i need to make this project.but i need the circuit diagram,

    Kindly put or send me the circuit diagram by email.



    Why can't you use the accelerometer incorporated into Android phones as a motion detector?


    4 years ago

    This is a very nice project...I'm doing research on a similar one like this, only this time, it's a CCTV camera that's able to transmit video and picture field to a phone and the phone being able to request for video or picture fields...I don't really know where to start though, but would really appreciate some pointers...


    4 years ago

    Pretty sure you're on to something here. Try getting a patent for the idea of having an alarm connected to the cellular network to be able to communicate with your phone.

    Like if the alarm goes off you can call the bike back and it's automatically on speaker. Or if you used a newer phone to could send it's geo-location to you if it senses it was being moved..


    4 years ago on Introduction

    hi sir, can you show me your timer circuit? im not very understand.. i want to create this device too..but i dont understand how the speed dial button is trigger for 3 second..

    1 reply

    5 years ago on Introduction

    How about a upgrade.
    buy the cheapest android phone you can find that has a camera.
    open the phone and desolder the camera and attach it to a bit of telephone lead. mount the phone into the plastic box with the camera lead and power lead coming out. glue the power lead in place. cover any holes on the box with hot glue and the back of the camera. install the speed dial hack as above. finally install camera remote app and a good find my phone type app. cable tie the box some where and hide the camera in the dash wire the power cord to the battery.
    put in a very low cost price plan like giff gaff. £5 every 3 months and its free giffgaff to giffgaff so your phone wont need credit to call you. if you get a call from your vehicle remote view the camera to get video or photos if it is being stolen to show who it is when it stops moving text the find my phone app to show you where it is then either call the police or

    1 reply

    Reply 5 years ago on Introduction

    If the thief disconnects the battery main wires before stealing, some rechargeable cells may be attached in parallel to battery somewhere hidden.


    5 years ago

    can i use a laser and a photoresistor? and when the laser is interrupted the cell phone sends a message or call to the owner of the car?


    5 years ago on Introduction

    Nice project. To avoid periodic costs associated with an active phone/prepaid phones, the solution is to not use a phone! Of course this is limiting as you need to have a receiver within range of a transmitter. I've built such devices using RF. You can have a handheld receiver with you that produces an audible alarm. You can also receive a text as well but you need a receiver (within range of the transmitter), connected to a computer with internet. With a distinct signal for movement, you receive one text (or alarm) for movement and another for out of range.


    6 years ago on Introduction

    Hello Sir, I am just wondering. My team is planning to have this mobile alert with our motion alarm. Is it possible for it? I mean, when the PIR will detect a motion or change in temperature, will it not just trigger the buzzer to sound, will it also trigger the phone to call a certain number?


    6 years ago

    Now I love the project it's awesome and very useful, the one thing that I didn't see mentioned (I apologize if I missed it) is that you'd have to have the phone on the bike/vehicle on a company plan to be able to send signal via speed dial correct? This would mean paying for 2 cell phone plan's so that you can receive the emergency on your phone you carry everyday as well as one on the phone sending the call, I'm just posting so I know if this is correct or not am I missing something here that you don't have to have the permanently mounted security phone on a plan so it can call out etc.?