My girlfriends car, along with another one in the same parking lot were broken into last night. They took her radio surprisingly without damaging the dash. From the neighbor's car they stole ID's and gift cards.

It's has my blood boiling and I know most thieves can disarm modern alarm systems these days. I was thinking of making something that would cause panic and make them bail before being able to steal anything.

One of my ideas is installing a set of super bright lights tucked behind the top part of the backseat where it meets the back window panel. Rig it to the some light switch that activates when the door is open and have the lights strobe incredibly fast and bright. Maybe even activate an annoying sounding horn. It could be turned on and off in the trunk and easily switched on when need be.

Any ideas on circuits and such to accomplish this? Thinking of using a separate power source as well.

  • You can try this one: youtu.be/uRNVxHPJ0hM Jul 3, 2016 at 22:24
  • Lol love that one
    – ohmmy
    Jul 3, 2016 at 22:25
  • 1
    Why a strobe light and alarm? That is basically what a typical alarm is. If you REALLY want to cause some panic activate a tear gas or pepper spray canister.
    – PaulB
    Jul 4, 2016 at 11:19
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    I'm voting to close this question as off-topic because there are very few countries where anything useful in this area would be legal
    – Rory Alsop
    Jul 6, 2016 at 16:47
  • 2
    @RoryAlsop I disagree, OPs initial question was asking about powering a strobe light, if anything, you should flag the comments that are straying into illegal territory. Jul 6, 2016 at 20:39

1 Answer 1


Basically, you want a device to activate when the 'system' is 'armed' and the door is opened. The easiest way to do this would be to tap into one of the outputs of an existing system, or install an aftermarket alarm system.

If you want a completely different system, you will need door pin sensors to determine when the door has opened. You MIGHT be able to use the existing ones, but that may interfere with signals to the Body Control Module (BCM)

To activate/deactivate the alarm, you can use either a keyed switch on the exterior of the vehicle, or a remote system. Not sure how you would set up a remote exactly, it might be easier to use an aftermarket alarm system. Alternately, look around at Arduino, xbee, wireless hobby kit stuff.

As for what the system activates... Anything physically dangerous is considered a 'booby trap' and illegal. You may be able to get away with a really loud horn/alarm. The best would be a video camera to record the thief. With the right equipment, you might be able to have it send you an alert when the alarm is triggered.

Consider what will happen with a 'false positive' when you forget to disable the alarm. You don't want to harm yourself, your girlfriend, her family, etc.

As for the radio, you may be able to secure it better so you need to remove a lot of the interior to get it out. This may lead to them just breaking more of your car trying to get it out. A removable face plate can be somewhat of a deterrent.

If you have an old cell phone, you can set it up so you can track it. Leave it in the car, track it, notify the police.

If you are worried about them stealing the car, you can put an additional switch on the start relay. Put a button under that dash that you need to press while turning the key.

  • Was thinking about adding some metal braces or chains around the radio to a strong secure part of the car inside the dash. What about inscribing on the radio something like "this is stolen. Call this number (insert local police number)" though I fear they could just grind it off
    – ohmmy
    Jul 6, 2016 at 16:10
  • Hard to say. If you make it too obvious, they will remove it. If you don't its possible no one will see it. That reminds me... check your local pawn shops for your radio.
    – rpmerf
    Jul 6, 2016 at 16:16
  • I have and been checking Craigslist. Even made an anonymous post of there informing buyers to beware. The idea of inscribing would be to make it obvious so if they tried pawning/selling they'd have a hard time
    – ohmmy
    Jul 6, 2016 at 16:17
  • @ohmmy document the serial number (if it has one) on the radio then it's non obvious and you have an easy way to identify stolen property.
    – Ben
    Jul 6, 2016 at 23:26
  • That way it can still be sold/distributed. Looking for a way that'd make their efforts worthless
    – ohmmy
    Jul 7, 2016 at 4:42

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