Welcome to this page on how to convert a every day Carbon Monoxide alarm with LCD screen into a GSM version that will call you when it Detects the dangerous gas Carbon Monoxide.

Now if you would like to see the Carbon Monoxide Alarm activate the Cell phone then visit my You Tube page here.

1). What is Carbon Monoxide this is a very dangerous gas that is found in the home and work place it is odourless colourless and has no smell and it is tasteless but it can kill you and your pets.

Now if you would like to know more about this very dangerous gas then Click here. Carbon Monoxide is also known as the Silent killer. 

2). Like all security devises they are only useful if you know they have been triggered and you can respond to them, In the case of Stand alone Carbon Monoxide alarms they run on batteries.

3). In the case of Carbon Monoxide alarms batteries can run low after they have been triggered you may come home or go to work and have a Carbon Monoxide leak as the alarms batteries have run down you may not know you have a leak.

4). In this simple design I will show you how you can convert a every day battery powered Carbon Monoxide alarm in to a GSM version informing you that you have a Carbon Monoxide leak on the premises.

5). In the Schematic below all the parts are off the self components you should not have any problem getting any of the electronic components.

This is the simple low voltage switch that will switch on the relay to activate the one touch dial on your cell phone to call you below.

I have designed the one below to be a non latching version.



Now a quick run down of the schematic diagram the first Diode is there just in case you connect your power supply with the wrong polarity, The Second diode is there to protect the Transistor from back EMF from the relay.

The 2k2 Resister is there to limit the current flow into the base of the transistor any voltage below 0.8 should not turn the transistor on so keeping the relay turned off.

In the photo below I have used the LEDs own power that back lights the LCD this is about 2.4 volts when the detector is in stand by mode the LCD is switched off so no current can flow in to the Transistor so keeping the relay turned off.

Now if the detector detected Carbon Monoxide gas then this would sound the sounder and light the LCD also sending a very small amount of current and voltage to the transistor remember the Transistor only needs 0.8 volts to turn it on and the LCD is giving us about 2.4 volts this will turn on the transistor and switch the relay on at the same time.

How the mobile phone works as soon as the relay contacts close this is acting like a switch and making the contact, One way you could look at it is if you have speed dial set up and you press a number key on your mobile phone it calls the number the relay is doing the same thing but automatically.

On your receiving Mobile phone put the contact in as CO Alarm so when the devise is activated it will send you the call and it will show up as CO Alarm this is the Carbon Monoxide Alarm.

In the version below I have designed a simple power fail safe circuit to power the circuit when the power is cut out or a black out happens.

Coming soon if you would like to see the simple battery back up circuit working then visit my You Tube page here.

I have designed the above devise to be built into your own circuits or as a stand alone battery back up power supply.

Here is the battery back up design connected to my first design for this project below.


The version below is designed to be a latching version.


The design below is the latching circuit with battery back up.

6). Now when you come to open your Carbon Monoxide Alarm be careful you don't snap any of the wires in side now in the photo below where why screw driver is touching the red and black wires take some of the insulation off the wires.

I have soldered my own connecting wire to the main circuit board as there are so many different designs out there if the Carbon Monoxide Alarm has a LCD built in then this will be back lit with a LED often blue.

If you are taking the covering off the wires then solder one wire to the red wire and the next wire to the back wire then using some PVC tape cover the connections on the wires or use a connecter block. 

7). Now after you have soldered your wires to the Red & Black wires in-side the Carbon Monoxide Alarm be very care fully put the alarm back together and press the test button the sounder should sound the same.

If you find the sounder is quieter then you have some thing pressing down on the Sounder the Silver component in the photo.

Now with your connecting wires coming out of the Carbon Monoxide Alarm this would be best to use RED and Black as this makes it simpler to fix to your Electronic Circuit.

I used Grey and White wires as I did not have any RED or Black wires at the time of doing this design.

8). Now after you have put the case back on press the test button the LCD should light up as normal showing the digits 000 PPM this is working ok see my photo below.

9). Now after you have built your little circuit up you will need to test it here is a simple test gig I used my self below.

My test gig is nothing more than the simple electronic circuit and a power supply for 9 volts connect the 9 or 12 volt power supply to the circuit the relay should not turn on.

Now connect the wire coming from the 2k2 resister to the + of the 1.5 volt battery and connect the wire coming from the emitter of the transistor to the - of the 1.5 volt battery if every thing is working ok then the relay will close.

Now if the relay did not close you will need to check your circuit is set up right and test the power of both battery if the 9 volt battery is ok then the circuit can detect a voltage as low as 0.9 volts this is below 1 volt.

Now in the photo below you can see the Carbon Monoxide Alarm is working as normal after the small modification to it's electronics.

Now when the unit detects Carmon Monoxide gas it will sound the alarm and show on the screen and at the same time close the relay contacts see photo below.

In the photo above I used a PP3 battery as my power supply you would be better of using a Mains adapter for 12 volts the battery was just for the demonstration.

Now we will look at how to modify a old cell phone for our Carbon Monoxide Alarm see the information below on how to do this.


Now you have all the things you need to modify your cell phone first we will need to load the mobile number into the phone make sure you have the ringer set to silent all so one touch answer turned off and one touch dial or speed dial turned on.

Now say if you put your own mobile phone number in number 5 and connected the wire coming from the relay to number five on the circuit board then this will call your mobile phone when activated. 

10). Now you will need to buy a Cell phone opening kit to get access to the phones electronics we are only interested in the pads under the phones keys see photo below.

You can get Cell phone opening kits from most electronic stores or shops or look on Ebay.

Now look at the pads you have an inside pad and outside pad solder one wire to the inside pad be careful the inside pad does not touch the out side pad and VS or you will get a short or bridge and you will need to use cleaning tools to try and fix it. .

11). Now when you come to fix your wires to the pad put one wire in side the pad and using your soldering Iron push down on the wire this will heat the solder so it fixes to the pad do the same with the next bit of wire but connect this to the outside pad see photo below.

In the photo above you can see I have soldered the two wires to the in & out side pads of the modified phone in the photo above I used my Nokia phone as this was a better photo than the one I used before.

You may also want to add a little bit of hot melt glue to the bottom of the wires to take some of the stress from the solder contacts see photo below.

Any phone with touch button and one touch dial/speed dial will work.

Items you will need are one mains operated timer switch to keep the mobile phone fully charged up.

1). Carbon Monoxide Alarm with LCD back lit model LYD-806 this is the one used in the project above order it from Amazon here.

Any problems then please do e-mail me at: Anthony@anthony-dacko.net I will be more than happy to help with this project.


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