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Smart kill switch
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Author:  Scales [ Tue Aug 21, 2012 11:24 pm ]
Post subject:  Smart kill switch
"Smart" Kill switch

Was thinking about making a immobiliser/kill switch for my zook today (our neighbor had 3 cars stolen a fortnight ago), and remembered my old car had a magnetic reed switch situation where I put a fridge magnet on the dash somewhere to disable it. Problem was, I had to keep the magnet in place for it to work.

Came up with this circuit tonight so that you should be able to swipe a magnet over the "sweet spot" where the magnetic reed switch is placed, put the magnet away, and the relay should remain "closed" until you start the car. It will also de-energise the relay automatically when the ignition is turned off.

You could make yourself a trendy Suzuki magnet and even keep it in the car somewhere obvious, no one would know what its for.


Feel free to have a go, I havent done it yet but will when i get a chance

Parts Required

*30Amp auto relay Jaycar
*Thyristor, this should work Jaycar
*470ohm .5w Resistor
*Magnetic reed Switch of some sort, of the normally open variety.
*Protection diode Jaycar

Circuit Diagram
Image

Apologies if its confusing for anyone.

Probably the best way of building it is on a small piece of breadboard and mount it in a small jiffy box.
Hide the box somewhere behind the dash. Then run some fly leads out to the reed switch, which will have to be glued somewhere behind a panel of your choice.
The relay can be put in the jiffy box too, or run some more leads out to remotely mount it in the engine bay if you wish.
You could also stick a 12vdc LED in there too to indicate that the relay is energized and you can start the car if you want.

The idea is that when the ignition is turned "on" with the key, the system is ready. you then swipe the magnet over the sweet spot, this will energise your isolation relay, closing the circuit to your coil, fuel solenoid, bomb, disco lights or whatever you have connected to the relay. You should then be able to start the car. After the ignition is turned off. the power to the thyristor will be removed and subsequently the relay will disengage automatically. The car wont start until you do the sequence all over again.


all of this should only cost about 15-20 bucks max. If anyone trys it and it doesn't work let me know, probably a case of changing a resistor value.


Sorry if this post isnt clear, I edited it somewhat before posting.


If/when I build one of these ill take some pics and update this thread.

Hope this helps someone from getting their pride n joy nicked. :beer: :peaceout:
Author:  Blakey [ Wed Aug 22, 2012 12:23 pm ]
Post subject:  Re: Smart kill switch
why not skip using the Triac as you have said to buy and just use the contact on the main relay to hold itself in so use the Main relay as a latching relay,

still have the reed relay so you can use it to energize the relay, but just branch off the N/O contact that you use to enable (whatever) to keep the coil also energized, once the ignition has been turned off again the relay will drop off as will the contact unlatching the relay and the system has been reset.

it will still be a magnetic swipe to enable and its less parts to go wrong and less parts overall so its cheaper.

there shouldnt be any problem with excess current also going throught the reed relay as your not starting the car with the reed relay closed so all current will be drawn only from the ignition relay.
Author:  Scales [ Wed Aug 22, 2012 2:48 pm ]
Post subject:  Re: Smart kill switch
I know what you are saying is making sense, but i've just come off night shift (notice my post times) Can you put it in a diagram so i can re-assess? im kinda in retard mode at the moment. been awake 22 hours at least now and had a few beers too so that doesnt help.

Cheers :beer:
Author:  Blakey [ Wed Aug 22, 2012 6:13 pm ]
Post subject:  Re: Smart kill switch
having a think about it it will only work with 2 contacts, and i think car relays only have one contact in them so don't worry about it. (unless you can get 2 N/O contacts relays for cars?)

but another way would be to use a small solid state relay to do it. but doing it that way might as well go your way.
Author:  Moph [ Wed Aug 22, 2012 11:06 pm ]
Post subject:  Re: Smart kill switch
I did this with an old Sigma using a latching relay ... it operated both the immobilizer and the central locking. Had a rare earth magnet on my keyring and hid magnetic reed switches under the interior trim on both sides of the windscreen. Just had to swipe the keys past and it'd unlock and disable the immobiliser, then lock and reactivate on the next pass.

Worked really well until one of the loose wires under the dash got caught in the manual heater / AC control mechanism, earthed out and fried it all :oops:
Author:  caboose [ Thu Aug 23, 2012 4:00 pm ]
Post subject:  Re: Smart kill switch
something like this
Image

when the relay is activated by the reed switch it will remain activated till the car is switched off

hope it makes scene :D
Author:  Scales [ Thu Aug 23, 2012 4:04 pm ]
Post subject:  Re: Smart kill switch
Yeah, same difference I guess. I was bored
Author:  rustyzook [ Fri Aug 24, 2012 9:03 am ]
Post subject:  Re: Smart kill switch
single relay version

Image
Author:  Scales [ Fri Aug 24, 2012 9:09 am ]
Post subject:  Re: Smart kill switch
One of the reasons I designed it the way I did is because most of the Reed switches cannot handle a lot of current. So you would end up blowing up the switch in some of these cases. ie its a low power version of a latching circuit. But hey, feel free to give it a go
Author:  rustyzook [ Fri Aug 24, 2012 9:18 am ]
Post subject:  Re: Smart kill switch
yeah fair enough, you can get 5 amp reeds from jaycar that would run the coil easy enough, but i didnt even think of the current loads,

so yes your was is prob the safest, good tech!
Author:  rustyzook [ Fri Aug 24, 2012 9:21 am ]
Post subject:  Re: Smart kill switch
what program do you use to draw your diagrams scales?
Author:  Scales [ Fri Aug 24, 2012 9:23 am ]
Post subject:  Re: Smart kill switch
Was some online design thing. Can't recall the site sorry
Author:  rustyzook [ Fri Aug 24, 2012 9:32 am ]
Post subject:  Re: Smart kill switch
fair enough it looks really good!, i use tiny cad, want a copy?

its free anyway
Author:  gvzookdriver [ Sat Dec 01, 2012 8:09 pm ]
Post subject:  Re: Smart kill switch
caboose wrote:
something like this
Image

when the relay is activated by the reed switch it will remain activated till the car is switched off

hope it makes scene :D


Could you use a spring rocker switch like this http://www.genr8.net.au/product-display ... uct_id=502 instead of the reed switch ???
Author:  Scales [ Sat Dec 01, 2012 8:11 pm ]
Post subject:  Re: Smart kill switch
switch is a switch... so yeah


well provided it can handle the current being put across it.
Author:  losfer [ Mon Dec 03, 2012 9:26 pm ]
Post subject:  Re: Smart kill switch
Don't know if this is any help but autospeed did an article on this in 2007. Google autospeed immobiliser. ... don't know how to post link from my mobile...

Sent from my Galaxy Nexus using Tapatalk 2
Author:  shakes [ Tue Aug 12, 2014 11:41 am ]
Post subject:  Re: Smart kill switch
How do you think this is doable with no constant 12v feed?

Looking at idea's like this for the moto which has no battery.

I just want to swipe the relay... Possibly leave the battery on until it starts and the stator is pumping enough to hold the relay shut?
Author:  Scales [ Tue Aug 12, 2014 11:58 am ]
Post subject:  Re: Smart kill switch
Yeah you'd have to run a battery. Then you would also need a regulator rectifier to charge the battery also. Not difficult to do. But may not be practical.
Author:  azzas15 [ Tue Aug 12, 2014 12:02 pm ]
Post subject:  Re: Smart kill switch
My last sierra had a weird kill switch. It was wired up so you had to pull up the hazard light switch to start the car. Worked well
Author:  shakes [ Tue Aug 12, 2014 6:46 pm ]
Post subject:  Re: Smart kill switch
Scales wrote:
Yeah you'd have to run a battery. Then you would also need a regulator rectifier to charge the battery also. Not difficult to do. But may not be practical.


Thanks. I'll be running LED's down the track which I beleive will need a rectifier.... Then I'll also need a capacitor or small battery, plenty of options these days. Lets me run a USB socket to charge my garmin or phone too.

I strongly dislike clutter and exposed or messy wiring which will make it a bit of a project but I reckon is easily doable. Guessing I'll be out of pocket at least a couple of hundred by the end of it though.
Author:  Scales [ Tue Aug 12, 2014 8:37 pm ]
Post subject:  Re: Smart kill switch
Be careful using a cap. I'd use a tiny 12v slab. There are some really small ones available
Author:  shakes [ Tue Aug 12, 2014 9:12 pm ]
Post subject:  Re: Smart kill switch
Scales wrote:
Be careful using a cap. I'd use a tiny 12v slab. There are some really small ones available


Yea I've just been googling them - Most say they are about a 1.5amp max charge rate. I'm guessing the XR is alot more than that. So then I also need to ad in a regulator for the battery too correct? All new to me. Any ones you can recomend?

Going to have to buy the bits n bench test it all. Time to learn electrickery. :lol:

Some googling also found me this and made me an internet expert.. Critique my list (already have some std relays, and I'll use a motorbike kill switch)

http://triumphspitfire.rickbaines.com/t ... mobiliser/

http://www.jaycar.com.au/productView.asp?ID=LA5074
http://www.jaycar.com.au/productView.asp?ID=SY4062
http://www.jaycar.com.au/productView.asp?ID=SL2644
Author:  shakes [ Sun Oct 05, 2014 9:13 pm ]
Post subject:  Re: Smart kill switch
So I ended up with this relay.

http://www.altronics.com.au/p/s4310-10a ... dle-relay/

Wired almost as per above but with different pin outs. My electrical base is poor at best, I can get the LED flasher working when auto relay is closed and it to switch the auto relay. But only with the push button. NFI how to get the reed to 'activate' the system so the push button only works after the reed has been swiped. (not having to hold the magnet over it permanently)

Have I brought the wrong relay or am I just a numpty ?
Author:  shakes [ Fri Oct 17, 2014 8:46 pm ]
Post subject:  Re: Smart kill switch
numpty it is.

http://www.the12volt.com/relays/relaydiagram12.html

I used a double throw as the relay on the left. Meant I could power/switch a flashing LED for when it's 'armed'

Now to work out a small battery or capacitor and how to charge it off AC
Author:  pezz [ Sat Oct 18, 2014 10:43 am ]
Post subject:  Re: Smart kill switch
I setup a similar thing on a customers car years ago, but I used a RFID card for activation
Author:  shakes [ Sun Oct 19, 2014 1:44 pm ]
Post subject:  Re: Smart kill switch
toyed with RFID but I'm to cheap.

Cheap enough I'm considering that a battery is too much effort, hide a basic push button switch and rely on a mechanical lock for security.
Author:  willis [ Tue Oct 28, 2014 10:24 pm ]
Post subject:  Re: Smart kill switch
I'm too cheap for a relay even. A suitably rated and quality on/off switch in the ignition circuit is enough for me considering if they are good with 12v and pop the bonnet the efforts are in vain anyway on these old cars.

A switch not easily "found" but within subtle reach of the driver, if they do decide to hotwire then the starter will crank and make a heck of a noise.

Wouldn't mind a fuel tap on the fuel line as a second defense, but if the car's being scoped and you are seen doing something like that it's a waste of time anyway. If it's parked up for a while there are heaps of things you can do to immobilise it, needs to be quick!
Author:  eldo [ Thu Dec 25, 2014 4:59 am ]
Post subject:  Re: Smart kill switch
Remove rotor button... Bingo
Author:  shakes [ Sat Dec 27, 2014 9:14 am ]
Post subject:  Re: Smart kill switch
Most pro thieves use trucks these days anyway, so a kill switch etc only stops the druggies/joyriders.
Author:  Andygoodbloke [ Fri Jul 04, 2025 3:15 pm ]
Post subject:  Re: Smart kill switch
It is much easier to hide a switch somewhere and cut the line which feeds into the negative of the coil and wire the switched line back into the coil
It took me about half an hour
Thanks Andy
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