Automatic engine locking help!!

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Hello all!

So I was building an alcohol detection system which renders the vehicle immobile when a certain threshold is reached. It works for DC motor. The system uses atmega32a and MQ-135. The problem is that I don't know what steps should I take to render the vehicle immobile. I searched on google and stumbled upon ECU but I felt that ECU is suitable for large applications (I found a guy whose ECU does wide variety of jobs). So please suggest me a direction to work upon.

Apologies if I have posted my issue at wrong place.

Thank you so much!!

Last Edited: Thu. Aug 3, 2017 - 11:43 PM
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You mean plugging into the CAN bus of a production vehicle?

 

Sure, folks do "snoop" on the inter-ECU/sensor CAN communication in cars but it's a whole other thing to start injecting signals that might disable the vehicle operation. Suppose you are driving at 70mph on a busy motorway and your circuit misbehaves and suddenly stops the car! Not a great idea.

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clawson wrote:
Suppose you are driving at 70mph on a busy motorway and your circuit misbehaves and suddenly stops the car! Not a great idea.

 

Don't mess with cars in this manner.

Paul van der Hoeven.
Bunch of old projects with AVR's:
http://www.hoevendesign.com

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Basically I need some sort of switch which can control the ignition of car or anything which inhibits the rotation of camshaft. A switch between ignition switch and battery may also work (I think!!).

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Paulvdh wrote:
clawson wrote: Suppose you are driving at 70mph on a busy motorway and your circuit misbehaves and suddenly stops the car! Not a great idea.

sigh.

Paul van der Hoeven.
Bunch of old projects with AVR's:
http://www.hoevendesign.com

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Seems like a dead end.

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What about this thing??

http://tiij.org/issues/issues/fa...

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noob_geek wrote:
a dead end.
Yup, that is exactly how this could end - nice pun!

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What clawson and pauldvh are saying is that whatever system yo devise it risks to trigger while the vehicle is driving at high speed. Since you are obviously not a professional regarding this application they are advicing you not to do this at all. Leave such things to the professionals.

If you need an alco-lock on a vehicle - buy one and have it installed by a pro.

"He used to carry his guitar in a gunny sack, or sit beneath the tree by the railroad track. Oh the engineers would see him sitting in the shade, Strumming with the rhythm that the drivers made. People passing by, they would stop and say, "Oh, my, what that little country boy could play!" [Chuck Berry]

 

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

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noob_geek wrote:
Basically I need some sort of switch which can control the ignition of car or anything which inhibits the rotation of camshaft. A switch between ignition switch and battery may also work (I think!!).

Not all cars have a camshaft!

 

You could intercept the power to the fuel pump (for fuel injected cars) or the more obvious is to intercept the ignition circuit. This makes it a safety critical circuit, so your magic box has be be reliable. You might want to check your local laws regarding this.

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Is your project doable?

Yes, absolutely.

There are lots of ways to prevent a vehicle from "starting".

 

Best if you detect that the vehicle is not already running before your circuit "stops" the vehicle.

 

Best if your circuit has a backup to monitor its behavior.

 

Best if your circuit can not, with any failure mode, disable the vehicle once it has started.

 

Best if...

 

The list goes on and on.

 

Vehicles, by the way, are a very harsh environment for electronics.

The electrical bus is very noisy and can have high voltage spikes, (Google Load Dump).

There are typically very large temperature swings, huge humidity swings, and more vibrations than you can imagine.

 

Have a quick read through Wikii Therac-25 for an account of a Medical Device with a software bug that resulted in deaths.

 

What-You-Dont-Know

 

The related problem here is that "What you know" is how to twiddle a few bits on a microcontroller, the green segment above.

 

Unfortunately, the yellow segment is much larger, and is the part that can get you into trouble!

 

JC

 

Edit: Typo

 

 

Last Edited: Thu. Aug 3, 2017 - 12:57 PM
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The green part of that pie chart should be about 2um wide.

 

 

Paul van der Hoeven.
Bunch of old projects with AVR's:
http://www.hoevendesign.com

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    I would consider a relay on the electric starter circuit (not the power one). This means that your device needs to detect alcohol very fast, otherwise the driver may start the engine which most people do after they get in the car. Once the engine starts, you should not interfere with it.

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Suppose you are driving at 70mph on a busy motorway and your circuit misbehaves

It will end pretty badly if you are traveling at 88mph and expect that big building to disappear because it wasn't there in the time period the "back to the future" calendar is set at.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Some of the ones here in the USA will stop the car while it's moving by killing the ignition.  THey monitor the speed of the car and wait until the vehicle goes below a certain MPH before killing power to the Ignition.  The way they primarily work is you cannot start the car UNTIL you blow into the mouthpiece.  If it senses nothing the car will start.  THen every 30 minutes an alarm sounds indicating you must pull over withing X amount of time, stop the car, turn the engine off then blow into the mouthpiece, etc.  Many of them now have cameras to show who is using the device to prevent someone from cheating the unit.

 

Implementation on the units vary from state to state here in the USA.

 

Your safest method would be to break the circuit to the starter until the user blows into the mouthpiece, then if all checks out light a green LED to indicate a pass and then allow the starter to operate.  THe kill relay costs about $10.00 and you can get them in any car alarm store.

 

Oh, keep in mind these devices can nullify your insurance policy should an accident occur and it is determined that your device does not hold any certifications from a government agency.

 

Jim

If you want a career with a known path - become an undertaker. Dead people don't sue! - Kartman

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB user

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Hi

In fact, I don’t want to be killed by an Atmega32a.. Please use a better MCU.

Last Edited: Thu. Aug 3, 2017 - 11:17 PM
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angelu wrote:

    I would consider a relay on the electric starter circuit (not the power one). This means that your device needs to detect alcohol very fast, otherwise the driver may start the engine which most people do after they get in the car. Once the engine starts, you should not interfere with it.

Good method. The typical interface is adding a series contact to the neutral safety start switch, that powers the starter motor relay coil.

Florida is a US state that requires vehicle imobilizer for dui offenders. Units exist, google dui imobilizer.

It all starts with a mental vision.

Last Edited: Thu. Aug 3, 2017 - 10:51 PM
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Quite frankly anytime one of these threads shows up I get nervous.  Based on the OP's prior threads, and the troubles in those, the idea of this device scares me even more, regardless of what country the OP is located in/  I also wonder what Micromel/Atchip thinks about having their MCU's involved in this endeavor.

 

I may be overreacting, but I am going to temporarily lock this and see what the other Mods/admins think about this.....IF they have no issue then it will be unlocked.

 

JIm

If you want a career with a known path - become an undertaker. Dead people don't sue! - Kartman

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB user

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