Dummy Security System -Sponsored by Farnell.com

You own an old car and would like to scare off thieves? Build your own fake security system!

I got all the parts i needed from Farnell Electronics! Also check out Element14!

Parts Required (All available @Farnell.com)Check out the links next to the components!

  • resistors: 1k, 10k, 680k   Resistors
  • capacitor: 10µF radial   Capacitors
  • LED: red superbright, 5mm diameter  LEDs
  • 7555 low power timer IC  7555
  • 8-pin DIL socket for IC
  • battery clip
  • 4.5V battery box for 3 AA cells
  • stripboard: 8 rows × 16 holes  Stripboard 
This Dummy Alarm project makes an LED flash briefly once every 5 seconds to imitate the indicator light of a real alarm. The circuit is designed to use very little current to prolong battery life so that it can be left on permanently. An on/off switch is not included, but could be added if you wish.  
See the whole circuit after the break:

The components I received from Farnell

All you have to do now is soldering together the components according to this circuit:

After soldering everything together it looks like this:

You can put this little circuit into a black hobbybox, add some batteries and place it inside your car! The flashing red Led will hopefully scare off thieves and protect your precious car!
I hope you enjoyed this little and simple how to!
Come back for another tutorial on how to build a simple fast flashing Led circuit!
The parts were sponsored by Farnell.com
Thank you very much!
Here’s a little video if you’re interested:


  1. Ahah! Nice trick! that will get the thieves away from your car. Reminds me when i got a window broken and they stole some of my stuff. Anyway, looks like you got a good feedback from farenell, i might buy the same pieces to (try to!) re-create the same thing! thanks for showing!

  2. Great post; I did something similar to this in school once, but this is obviously more complex than that ;D

    Also congrats on the sponsor man, if anyone deserves it, it's you and your engineering mind.

  3. great instructable! I'm not that into electronics but that seems to be pretty easy stuff! Also thanks for the links to the great shop +1 ! I'd never have known where to purchase these!

  4. Hey, that was pretty easy to rebuild!! And farenell delivered the parts in good time, i didnt have to wait long for them 🙂
    Thanks for the tutourial-vid, it was very helpful!

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