Introduction: Hack a Wireless Doorbell Into a Wireless Alarm Switch or On/off Switch

Picture of Hack a Wireless Doorbell Into a Wireless Alarm Switch or On/off Switch

I recently built an alarm system and installed it in my house. I used magnetic switches on the doors and hardwired them through the attic.The windows were another story and hard wiring them wasn't an option. I needed a wireless solution and this is what I came up with thanks to some helpful tips from the guys at

Step 1: Required Parts and Components

Picture of Required Parts and Components

(1) wireless doorbell kit (get the one with the longest range that you can find with a button and the receiver)
(1) npn 2n2222 transistor (any small signal npn transistor should work)
(1) magnetic NO (normally open) alarm switch
(1) roll of double sided tape.
shrink wrap or electrical tape
3mm drill (bigger is ok, it's just for running wires trough the cases)
24 guage wire ( approximately 2' (60 cm))
soldering iron and solder

Step 2: Prepping the Receiver

Picture of Prepping the Receiver

1. Start by removing the back of the doorbell receiver. That is the part without the button.

2. locate the small speaker. It should have two wires running to it.

3. Solder a 3" (8cm) wire  to each of the terminals on the speaker if you want to keep the chime noise. If not just unsolder the existing wires from the speaker and use them.

4. The 2n2222 transistor is set up like this.                                 Solder one of the wires from the speaker to the emitter leg of the transistor and the other wire to the base leg of the transistor. Attach a 12" (30cm) piece of wire to the base leg and a 12" (30cm) piece of wire to the collector leg of the transistor.

5. Use shrink wrap or electrical tape on all of those joints so that they don't touch each other and short out.

6. Drill a small hole in the case and run the two 12" (30cm) wires out through the hole. The 12" (30cm) wire from the transistor base is you negative or ground connection. The 12" wire from the collector leg of the transistor is the positive connection. I ran mine through the mounting hole since I won't be using it.

7. Put this aside for now and move on to the button prep.

Step 3: Prepping the Button

Picture of Prepping the Button

You now are the proud owner of a great wireless momentary switch. You can make it into a latching on/off switch for use with many different items by adding the simple flip-flop circuit shown in the photos.

To use it as a wireless alarm switch for your security system though we will have to complete a few more steps.

1. Locate the button part of your wireless doorbell. Open the case (varies for different brands) and find the small tactile button located on it.

2. You can check with a continuity tester to be sure it is a NO (normally open) switch which means that if you press it, it will allow current to flow (or make your continuity tester beep or light up). If you release it, it should open and stop the current from flowing.

3. Drill a small hole in the side of the button case or housing. To make it easier on myself, I removed the remaining plastic from the hole area and made it into a notch. Thread the wire from the magnetic alarm switch through this hole (if you left it as a hole) and to the momentary tactile switch. Cut the wire and strip it so that it can be soldered to the momentary switch poles. Remove the circuit board from the case and locate the momentary switch terminals on the solder side of the board. Some tactile switches, like the ones shown, have four poles. There are still only two that you can use as the poles are connected to each other. on either side. I made this one for a double window, so I used a magnetic switch on each side. Either window will trip the alarm.

4. Solder one of the wires from the magnetic switch to one of the terminals of the momentary tactile switch and the other wire to the other terminal. It doesn't matter which wire goes to which terminal as long as they are not two of the terminals that are connected within the switch.

5. Test your soldering by putting the magnetic side of the magnetic switch next to the side you just soldered. The chime should sound if you left it connected.

6. reassemble the doorbell switch and apply double sided tape to the back of it and the back of the magnetic switch that is wired to it . Stick the switchs to the frame of the window that you want to protect. Use double sided tape and stick the magnetic portion of the magnetic switch to the window sash with the bottom of it level with the top of the wired portion of the magnetic switch. This will allow the switch to close and the alarm to trigger as the window is raised. It will only be closed momentarily as the magnetic portion slides past the wired portion of the magnetic switch. That is all you need to trigger the alarm and it uses almost no battery since the switch is only closed for the brief moment that the magnet slides past. This also allows you to open your windows without the contact draining the battery when the alarm system is off.

Step 4: Conclusion

Picture of Conclusion

You can make as many of the button switches that you want for all of the windows that you want to protect. For $7.00 usd apiece, I was able to buy just the buttons for the wireless doorbell that were on the same frequency. I used two magnetic switches on one button for the double windows in my house.

You might notice an extra wire coming out of the receiver. I added that as a longer antanae to try to increase the range a little bit.

If you have problems with the alarm triggering from a neighbors wireless doorbell you can follow the directions included with your doorbell on how to change the frequency.


mrq55 (author)2017-01-28

Jman, is the extra wire in the receiver connected to anything? Or just hanging out in the receiver box attracting the wireless signal from the button?

kgreene8 (author)2014-11-07

Hi. I need some help. Im using this to trigger a timer board for a model railway. The timer board needs a 12v supply, door bell need 5v so im using a voltage regulator. When i hook it all up the door bell burns out... So i tried adding a 3volt relay to the common and + of the transistor and it killed the door bell... Help!

JoshuaW9 (author)kgreene82015-03-04

While you can usually use voltage regulators as you've described, it sounds like your wiring may be askew, or possibly something got in and is shorting on the pcb. There isn't really much reason the bell should burn out. All you're doing in drawing power *from* it for the relay. In any case, you may want to have a look at optical isolators. Essentially an led, ldr, and (sometimes) transistor in an IC. They ensure complete electrical separation of the two circuits. You can buy them anywhere, or if you like, salvage them from lots of things (check out transformers, computer PSU's and the like)

fred41 (author)2011-12-12

I'm really interrested in your work, great job, I own a wireless door bell, but it doesn't produce a simple long sound, but 3 short bip, do you think it could work with your hack? If not do you know a solution to adapt it?


dagob (author)2011-02-25

Will the transitor keeps the alarm on untill you swithc it off?

deamonlord (author)2011-01-29

What can I do to simply on/off the lights in my room wirelessly? Obviously this wont work on high AC voltage but what will?

cwatts22 (author)deamonlord2011-02-08

You can just use a relay switch with this method to control high volt ac voltage.
Just wire this to the relay's input and the high voltage as the output.

verdastel (author)2010-12-31

Cool project with affordable cost!
What do you think if you integrate IC 555 in the controller to control the frequency of the triggering signal (thus variable with some switches), and integrate IC LM2917 (frequency to voltage converter) to the receiver to turn it into a "several channel remote system"?

vinz.arthur (author)2010-10-24

should i still put a transistor even though it's not for the alarm?

jman 31 (author)vinz.arthur2010-10-25

Yes. The transistor is the key for turning the alternating current into a usable dc current. I will try to draw up a quick schematic for you when I get a minute to sit down.

vinz.arthur (author)2010-10-24

I need it for a project. Does the voltage will stabilize with the transistor?

jman 31 (author)vinz.arthur2010-10-24

I'm not sure what you are asking. The 220 voltage will be stable if that is what you mean. The voltage that you apply to open and close the relay will need to be a stable DC 5 volts. You can either use a battery for this or get/make a 5v circuit that works off of the 220. That is what I would do. There are plenty of DC wall jacks (wallwarts) that you could use for this.

vinz.arthur (author)2010-10-17

Is there other way to make it a switch for a 220v socket?

jman 31 (author)vinz.arthur2010-10-18

Probably cheaper and easier to get one of these:

jman 31 (author)vinz.arthur2010-10-18

Sure. As long as your relay is rated for 220 you can put whatever you want on the switch side of the relay. You will want to put a fly-back diode on the low voltage side of the relay. You can Google it, but a quick search brought up this page: Be careful if you are new to this working with mains level voltage. You might want to get someone that is familiar with it to help you if you aren't

vinz.arthur (author)2010-10-16

Hi I would like to know what is the output voltage to the speaker? I want to convert it to a relay switch instead of the speaker. By the way I'm a newbie another question is what is the purpose of the transistor. thanks( I wish I would have the reply as soon as possible)

jman 31 (author)vinz.arthur2010-10-16

The output voltage is variable with the sound so there is no way to just use a relay switch. You can however add a battery and feed power through the transistor so that it completes the circuit and closes the relay. Pretty simple to do. The transistor is there simply to turn the variable pulse from the speaker outputs into a basic on/off switch. When there is no sound, the transistor is open. As soon as there is sound it causes the transistor to close, completing the circuit for the alarm.

vinz.arthur (author)jman 312010-10-17

Thank you very much for that information!

vinz.arthur (author)vinz.arthur2010-10-17

Follow up question, Is there any other way to make a switch for a 220v socket? I'm sorry for annoying you.

Lydboots (author)2010-10-06

Hi - I don't quite understand your title (regarding the "switch")
can you tell me if this would do the following job please:
I want an alarm to go off at some distance away (wirelessly) when a door opens
not a door bell but an entry alarm

jman 31 (author)Lydboots2010-10-09

All this instructable does is replace the magnetic switch that would normally trigger an alarm with a wireless one. You still either have to build or buy the alarm system. Sorry it took me so long to answer this, I missed it somehow. Let me know if you are still confused by this.

fungodude (author)2010-06-10

I have a wireless doorbell with 2 speakers. Does this matter??? Do i just hook up the transistor to one of the speakers or what???

jman 31 (author)fungodude2010-06-10

Yes. The doorbell puts out alternating current in the form of sound waves. You use this current to "turn on" the transistor. I would check and make sure the sound is indeed coming out of the speaker that you decide to use. Let me know if you have any other questions.

fungodude (author)2010-06-10

I have a wireless doorbell with 2 speakers. Does this matter??? Do i just hook up the transistor to one of the speakers or what??? Please Help.

matchett (author)2010-02-23

what is the point of having th transistor, and if im just hooking two wires to the ones that go to the speaker do i still need it to turn it on/off? thanks

jman 31 (author)matchett2010-02-23

The transistor turns current from the bell into a momentary switch that the alarm can use. The alarm doesn't trigger from current, it triggers from the completion of the alarm circuit which the transistor provides.

Not sure what you are referring to on the second question. Could you elaborate a little? Turn what on/off?

matchett (author)jman 312010-02-27

i am making an airsoft gun that fires remotely. i have two wires that when they touch it shoots, so i was going to hook the up to the wies that run to the speakers. so when the bell is suppose to ring it will hopefully shoot.

jman 31 (author)matchett2010-02-27

Yep, you need the transistor. That is the same situation. You have turned the wires into a momentary switch. Any small signal npn transistor should work for that. Just look at the datasheet so that you get the pins right. You don't want to just connect the wires to it because it will be shorting the bell directly to ground. If you get a transistor and you need help with the pinout, just let me know.

jman 31 (author)2010-01-04

Thanks guys.

Wolf, when time permits I will see about editing step 3.

Stephenniall, I hope you will post you work so we can enjoy it. I built my alarm system from this pdf. . It seems to work really good so far. You have to have a basic knowledge of putting a hex file on an IC though and some electronics experience. You can get all of the files for this alarm system here on my little DIY forum.
You may have to register to view the files. All of the files (including programming) are included in the zip file.

stephenniall (author)2010-01-04

Smart Idea !

Im currently designing a Cheap multi room alarm Thats cheap (under 10£ about 25$ ) to make

Wolf Seril (author)2010-01-03

Very cool idea, well done. Consider splitting step three into a few more steps, though.

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