Cloning an infrared disarming remote of a $8 home security system


[Sylvio] decided to buy one of the cheap alarm systems you can find on the internet to have a look at its insides. The kit he bought was composed of one main motion sensor and two remote controls to arm/disarm it.

Communication between the remotes and the sensor is done by using infrared, requiring a direct line of sight for a signal to be received. Modern alarm systems typically use RF remotes with a typical frequency of 434MHz or 868MHz.  In his write-up, [Sylvio] first tries to replicate the IR signal with one of his ‘learning remote controls’ without success and then proceed to reverse engineering the remote circuit shown in the above picture. Hackaday readers may figure out just by looking at it that it is a simple astable multivibrator (read ‘oscillator’). Its main frequency is 38.5kHz, which is typical for IR applications. Therefore, if one of your neighbours had this ‘security system’ one could just disarm it with any of the same remotes…

[Sylvio] then explains different ways to replicate the simple IR signal, first with an Arduino then with a frequency generator and finally using the USB Infrared Toy from Dangerous Prototypes. We agree with his conclusion: “you get what you pay for”.

4 thoughts on “Cloning an infrared disarming remote of a $8 home security system

  1. Funny enough I picked one of these up just last week to replace a blown PIR. I figured that PIRs are expensive and I didn’t want to wait for any delivery so I thought I could hack the one here and connect it over I2C by using a attiny. (did it before and worked). that’s 10$. sure maybe it has a little better range but I don’t really care for that.

    If you look at all the components inside and the prices in these “electronic shops” you actually get an amazing deal. So you get way more than what you pay for IMO.
    the batteries and housing alone would be more than the 5$ I payed for it. And the piezo alarm is incredibly loud.

    Once I have it connected to the network I can disable it any way I like so the standard IR vulnurablity is no big deal.

  2. I also picked up one of these cheapo alarms a couple of days ago, the first thing I did was crack it open to see what was going on inside and when I realised how simple the design was I got out my galaxy note 10.1 and started blasting ir codes at it, and wasnt surprised that it could easily arm/disarm it. For £4.99 though it’s a bargain box of components.(b&m bargains uk, if anyone wants to pick one up)

  3. Since it’s IR and mounted inside nobody knows you have an easy to disarm security system since they don’t see you disarm it. Unless they are friends but one assumes those don’t try to rob you.

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