How to build a low-cost GSM door opener

In the last days I once again tinkered a bit. Certainly more bad than good, but where are no professional tools, there won’t be high quality. But the ultimately goal was not a professional product, but rather a simple and cheap solution. But what is it all about?

The product of my tinkering is a low-cost GSM door opener. That is simplified a small device, that opens your door when you call it and may bring the costs next to nothing. And now a little about the implementation …

Anyone who wants to get an overview about the project, can view the following video, which I made from the final product.

To build a similiar application you need the following components:

  • Nokia 6230i
  • 12V relay (a 5V relay would be better, but I had none)
  • Connector strips
  • A few wires
First I disassembled the phone and removed the vibration motor. To the now vacant contacts on the phone board I soldered two wires and assembled the mobile again. From the disassembly process I unfortunately made no photos, but those who need help, can read on this page how to disassemble a Nokia 6230 professionally.
Then I soldered the two ends of the cable (coming from the connection of the vibration motor) to a relay. As I have noted that there is just ~ 1.2 volts on the lines from the phone  and my relay needs at least 9 volts for switching, I opened the relay and “slightly” stretched the spring such that the relay now also switches with the 1.2 volt from the phone.
(Sure this is not a perfect solution and every electrician would probably split me in thousand pieces, but for a feasibility study, as this project is, it is sufficient.)
low cost gsm door opener (1)  low cost gsm door opener (2)  low cost gsm door opener (3)
At this point we are already so far that the relay switches every time the phone had been vibrating. Now I just had to disable all the warning sounds, etc. on the phone which could have triggered the vibration motor unintended and create a caller list. This caller list contains all the numbers which should be allowed to open the door.
Last but not least, Iset up the Nokia 6230 in that way, that only participants from the just created caller list can trigger the “vibration motor”. This ensures that only approved people can address the relay and thus open the door.

In the final step, the relay has to be connected to the switch located on the corridor to open the front door. Once this is done, the absolute low-cost door is already available for use.

All in all, the project cost me just ~2$ for the relay. All other parts were still laing around in my flat.

What do you think of the project? Have you also ever implemented something like this or even thought about it?

Greetings,
Raffi

15 Comments

  1. Ferkeltodsays:

    Nice work, could you post a diagram how to solder the relais? Thank you.

  2. Rahulsays:

    Hi,
    With out stretching the relay can you suggest me an alternate procedure to power the relay by stabilizing the voltage

  3. Michaelsays:

    Hello i saw the idea its very clever and i like it. I try on an old phone but i face a problem. Vribrator give three tone and relay switch goes on off three times. Have any idea how to have only one tone?

  4. anisays:

    Hello ,
    iam trying to build one like this door opener that without success.
    i bought a relay , diode and a 8v battery. connected the wires (i saw a video) but the exit 9v plug does give energy when the vibrator is on.
    Please i u contact me by email , i can upload some pics how i did.
    Best regard
    ani

  5. Viveksays:

    Cant we use a dv step up device?? instead of stretching the spring??

    • You could try it. But I’m not sure if the phone has enough power/ampere. So just try it.

  6. cavansays:

    what ill have to do is go online n see what they have and have a chat to some electricians about what i could do, u have any idea on what the name or model type of relay u used? and would it be better to go for 5v or 12v n stretch it?

  7. cavansays:

    hi i have been thinking about making somthing like this myself, im no pro in electronics but i have a hidden safe in my wall and a second secret door which opens to keep it hidden, now i saw vids on mobile use and alot use the vibrator but that doesnt give a constant flow so does it actually work well if i took the vibrater off n wired to the phone contacts?

    • That’s exactly what I did. Otherwise you could use an Arduino+Relay-Shield+Cheap Ethernet Shield. All together maybe costs 20-30$. Then you could switch your devices via Ethernet or Wifi/Internet if you connect the Arduino to your router.

      • cavansays:

        thats way to complex with this whole arduino stuff lol i just wanted to make sure i dont get the cheap bits n find out i bummed it up lol thanks, guessing u hooked it up to an electric strike lock or somit to unlock?

        • Yes, it’s connected to an alectric strike lock. But don’t be afraid. The Arduino stuff isn’t that complicated you may think. ;)

          • cavansays:

            ok so most strike locks are powered by 12v and most mobiles poweroutput thru the vibrator connecter is as u said 1.2v+ so what sort of resistor would i be looking at to function?

            • cavansays:

              no resistor i ment relay sorry

              • I took one from my toolbox. ;) It’s one, which was meant to be used for in-car-use. I had to open it and strech the spring inside, so that it switches/changes states with lower voltage.

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