RFID Car immobiliser

Hi All.

I want to build an RFID immobiliser for my car. How I would do this is hack into the 12v starter solenoid circuit and use the Arduino to break the circuit to the starter motor so the solenoid cant be engaged.

What I don't really want to use is a relay as the circuit will be activated anywhere from 30mins to 4+ hours to allow start-stop features and auto restart after a stall on my journeys, and I don't want to burn the relay out!

Is there an alternative to a relay that can handle switching a 12v 30a circuit?

Cheers,
Mike.

TBH, car thieves these days won't have the time or knowledge to hotwire new cars, they just buy the gadgets to mimic the key fobs and steel them that way. The Arduino will be hidden away and all wires incorporated into the existing looms. It just adds a 2nd level of security.

s200bym:
TBH, car thieves these days won't have the time or knowledge to hotwire new cars, they just buy the gadgets to mimic the key fobs and steel them that way. The Arduino will be hidden away and all wires incorporated into the existing looms. It just adds a 2nd level of security.

If they are relying on mimicing the keyfob then then @Delta_G's idea still works.
Another option is to fit a hidden on/off switch to the fuel pump.

The fuel pump is another option I considered and maybe both together. With regards to hacking into the ignition switch, it is a push button start and without having the proper wiring diagram I can't really hack into it as it is not like a key switch.

Maybe something like this instead of the relay?

https://www.ebay.co.uk/itm/High-Current-MOSFET-Switch-Module-DC-Fan-Motor-LED-Strip-Driver-Steples-DE/221650858247?hash=item339b6bb107:g:GA0AAOSwc0FUplI1

It is probably a good idea to have proper wiring diagrams before making any modifications. I would advise keeping things as simple as possible (e.g. just a switch) and remember that if your car does not start you may need to undo your immobiliser/s.

Another factor well worth considering is your vehicle insurance. If your car catches fire the first thing the insurance inspector will do will be to ask if the electrics had been modified in any way e.g. new sound system etc. etc. They will check the fuses and they will look for modifications. Your immobiliser may be completely innocent and it may look like a completely professional job but its presence may make for an uphill struggle with an insurance claim.

Yeah, I see what you mean. Maybe I should just get an autowatch ghost fitted that disables the canbus system.

I still might make the circuit just for fun with out fitting it to the car just to see how it would work/hold up.

Consider the likelihood that a software glitch may immobilise your car in highway traffic.

Paul__B:
Consider the likelihood that a software glitch may immobilise your car in highway traffic.

and if you do get towed make sure you take the steering lock off before you reach a bend or worse a roundabout :slight_smile:

A simple hidden switch is probably perfectly adequate. Car thieves are in a hurry - if they can't find it in 30 seconds they'll give up.

In any case modern cars usually have a security RFID device built in to the key - even with a special forging gadget it would take a very long time to go through all the permutations, so I bet they're not much used. And I bet that the reader in the car will go away and sulk for eg 1/2 an hour if it gets more than a certain number of successive false reads.

Pain in the neck as they are when they go wrong, modern car security systems , though not perfect, are good enough to have reduced the number of thefts very considerably over the last 15 years or so.

Allan

ps A friend of mine used to run a fleet of lorries. His anti-theft device was a hidden 3-way tap in the fuel line. When turned to 'off' it drew air, so a potential thief wouldn't get very far before the engine stopped. It then couldn't be re-started without the laborious procedure of bleeding all the fuel, pump and injector lines .

Beware some of this stuff on newish cars . On the BMW for example , it uses a variable speed drive on the fuel pump to control the pressure in the fuel rail . If you inadvertanly tried to start the car , forgetting you’d turned the pump off , it would generate an engine fault, needing an OBD2 scanner to reset it and turn the fault light off . If you isolated the starter , I could foresee a similar issue.