DIY Immobiliser (self arming) (1 Viewer)

[lkortbeek]

Can someone review my electrical design and tell me if it will do what I think it should? (sorry about the long post)

I've scoured this forum and a few other places looking for an easy vehicle immobiliser to stop people walking off with my cruiser. I had a few goals in looking for a design: There shouldn't be any indication that there is an immobilser, and the system should reset itself (I find myself somewhat easily distracted and absent minded in my advancing years). Based on the research I've developed the attached circuit. Here is how I think it works:

1) power normally flows through a fuse, through the normally closed contacts of a relay, through the time delay circuit to two parallel relays
2) the first relay ground feeds to a hidden reed switch (either behind the plastic cover over my radio opening or my center console)
3) Tripping the reed switch with a magnet, closes the circuit to ground and activates the relay, closing a second path to ground, thereby keeping the relay energized
3a) Tripping the reed switch also energizes the second parallel relay. This closes the ignition circuit and allows the vehicle to run, whereas otherwise it will only turn over (no amount of jump or push starting will work to make the engine run)
4) A feedback loop will also keep the parallel relays activated even when the immobilizer power shuts off (next step)
5) Put the key in the ignition and turn the key to run or start. This applies power to the coil of the first relay and takes power away from the immobilizer circuit. The parallel relays stay active due to the feedback circuit in 4 and the vehicle stays running
6) Turn off the ignition. This stops the flow of power to the coil and allows the first relay to de-energize, basically de-energisiing all the relays
7) Power again flows through the normally closed (first) relay into the delay-on circuit. This provides a momentary delay to allow the second, parallel relays to de-energize and isolate the ignition
8) After the power-on delay (should be ~30 seconds based on the what I have read for teh size of the capacitor) the immobilzer is re-armed and ready for me to hit the reed switch with my magnet.

I am not an electrical and cobbled this together from various posts. Hopefully someone can tell me if this works the way I think it should. I am also looking to see if I can't make everything solid state (see G-spot from NZ - http://home.clear.net.nz/pages/dandavies/tech info.htm) instead of electro/mechanical but the world of SCR's and transistors is too foreign to me.

Thanks for any help

 

[spotcruiser]

Wouldn't a kill switch in a hidden or locked location be easier (Without seeing what you've posted. I'm still waiting for the provided info to download and open)?

Circuits can fail and tend to at the worst possible moment (say, on a steep hill climb). Not that a kill switch is infallible, but it's less likely and it's easily jumped by the owner that knows where to install the jumper.

Or, perhaps a fuel shutoff valve. It lets a thief get 100 yds away before it dies. Or, a clutch pedal lock. There are even commercial kill systems that use an electronic fob, similar to a lot of new vehicles.

Don't get me wrong, I'm a do it yourself guy, but I think a kill switch is plenty effective.

I give up. I'm not waiting any longer for the link to download.

 

[lkortbeek]

I thought of a kill switch inside a locked console but I am self aware enough to know I'll forget to set it. Either that or my teenager will forget when they borrow the vehicle. I like the self reset because I really just turn it off and walk away

 

[spotcruiser]

You just need to establish the habit of using the switch all the time. It's like using seatbelts.

I thought of a kill switch inside a locked console but I am self aware enough to know I'll forget to set it. Either that or my teenager will forget when they borrow the vehicle. I like the self reset because I really just turn it off and walk away

 

[78fj40mg]

Great idea Lloyd! I've been thinking about some type of alarm or self arming immobilizer, unfortunately I don't have the electrical/electronic expertise to develop such a devise. I'll follow along with the hope that something materializes in the near future.

 

[lkortbeek]

Here's a picture of the circuit in case the pdf doesn't load.

 

[78fj40mg]

What's the color code for your diagram?

 

[JohnnyC]

I just reach under the dash and pull the ignition fuse off one one side and leave it sticking straight out...

Push it back to start it

I only had to do this a handful of times... Mostly when living on LI ny

 

[lkortbeek]

Not really up to any specifications, but the colors were my guide to what happens when. Red is power both switched and unswitched, the green is delayed power, the black is ground. Solid color is what I start with, the dotted lines represent connections after the relays activate (sort of) - did I mention I am not an electrical type?

I'll post a real wiring diagram once I build it.

 

[Solace in Solitude]

I have a hood-lock/ignition interrupt (that I bought and installed). When it's active, the starter will whine and whine and the engine will never start. Eventually the battery will run down, assuming someone actually tries that long.

I have yet to forget to activate it.

However, I have YET to remember that I activated it - I just sit there trying to start it and eventually (thus far, before I run the battery down) remember it

Then, I look sheepishly at Gunner and he has that amused look on his face

So, while I can't, with any certainty, say that it has prevented a potential theft... it certainly works

 

[snaggletto]

Simplicity is always the best and most reliable. While your circuit sounds like it would work, a simple hidden kill switch would be just as effective and many times more reliable. Remember, one could simply tow your truck away if they wanted.

 

[jim land]

you can use the clutch pedal swich from a 4runner or taco ,but instead of being behind the pedal you can hide it on the side of the seat or under the dash, so you need to hold it when you start , and from the same donor vehicle is a clutch cancel switch to disable the system if need

i hope you understand what i mean

 

[Solace in Solitude]

But, given proper preparation, it could raise a hell of a ruckus, as it's being towed away...

We can always overthink this and I fear you may be overthinking it, Lloyd...

But, in the end, it's you who have to be satisfied with whatever solution you implement.

I'm all-things-especially-electricity-challenged... But Rudi ( @bj40green ) is an electrical genius... Maybe he has time to critique your schematic.

 

[AlaskanWheeler]

How about using a proximity key alarm system?

 

[MrMoMo]

That is a heck of a complicatd system. Why not just put a switch on the dash marked "lights" and actually have it cut the ground (or supply) for the coil? Engine would crank all you want but no spark, no run.

 

[PixelWrangler]

I've been using a similar system for the past four years, a couple of relays and a hidden magnetic reed switch to deactivate. I use a kill switch with mine and leave it in plain sight on my dash since toggling it won't do anything without activating the reed switch. It also looks like just another light switch, that apparently doesn't work. My system uses both a regular Automotive relay and a DPDT relay. There's also a flashing LED to indicate that it's armed, more to remind me to deactivate it, but also I want visible evidence that would be thieves need to move onto the next vehicle. I'm no electronic genius either, but I can follow directions, solder and plug stuff in.

I've only forgotten to active the system a few times, but since I also remove my steering wheel at night I'm not too worried about it. If I must park for an extended time or somewhere sketchy I also have a hidden fuel shut off valve.

My girl gets to live on the street somewhere in the greater Los Angeles area, so I take a few precautions without going overboard. I also leave her a little ragged looking.

 

[bj40green]

Geachte Heer Kortbeek.... just kidding.....
Lloyd, where did you get this diagram or did you create this yourself?
I've marked your relays with #1, #2 and #3 in this picture.
I'm afraid that this concept is not going to work. Let me explain: The switching logic as in "auto reset" will work I think ( I have to double check that) but the "(re) connect the IGN coil to the 12V power" part will fail due to the fact that the coil from relay #1 (red line) is now in series with the IGN coil.
The resistance of the relay coil will limit the voltage (and thus the current) to the IGN coil. In other words; if the resistance of both coils is the same (which they are not) then each will get 6V. Not enough for the relay to hold and not enough for the IGN coil to work.
BUT........................ the resistance of the relay coil is much higher than the IGN coil so the voltage dividing wil end up 70/30 or something like that. And another thing is that the voltage output from relay #3 to the IGN coil (red dotted line) will be too low to feed the loop back with diode D2 to keep both relays activated.
The diagram has to be modified (not done yet) in a way that the IGN coil get's 12V from relay #3 but now from the ignition key.

BTW on every diode you loose 0.7Volt.

Rudi

 

[sggoat]

I have a hood-lock/ignition interrupt (that I bought and installed). When it's active, the starter will whine and whine and the engine will never start. Eventually the battery will run down, assuming someone actually tries that long.

I have yet to forget to activate it.

However, I have YET to remember that I activated it - I just sit there trying to start it and eventually (thus far, before I run the battery down) remember it

Then, I look sheepishly at Gunner and he has that amused look on his face

So, while I can't, with any certainty, say that it has prevented a potential theft... it certainly works

I think that when you are going out on a trip, the first thing to do is say to Gunner "are we ready?" if he barks and shakes his head-then go. If he kinda whines and is a little hesitant, you better start checking

 

[JohnnyC]

If he kinda whines and is a little hesitant, you better start checking

Or... Let him out ... He needs to pee

I am even thinking you could disconnect the connector at the bottom of the harness for the ign switch... Or put an inline switch someplace near from the ign switch

 

[Weber Sarge]

I agree , either a hidden switch or just put a full alarm on it . I'd bet a lot of the ones that are stolen are loaded onto a trailer .
Sarge