Car Ignition

[dreamproject]

Hi all,


I was using relays to switch all kinds of home appliances on and off and it suddenly struck me if I could use a relay to control access to a car's ignition . I have already got a PC installed in the vehicle . Could I write some sort of an interface program to accept a code from the user , which would switch on a relay (wired in series with the ignition fuse) , through the parallel port . Are relays suitable for this purpose readily available ( standard 12 relays ) or are special ones required ? . This would be a really cool project. 8) . Kindly advise.


Thanks

 

[musthave]

why not. write a couple of commands to have your car windows roll down or have the lights come on at a preset time, youre only limited by your inspiration. but always uses propperly rated relays for the load it will control.

 

[Roboticinfo]

reply

This is a really easxy project but let me ask you this, does your computer in your car have a parallel port?

Or maybe a serial port?

 

[tansis]

Ordinary mechanical relays are fine for this application, you will need a small transistor drive stage between the computer port and the the relay, "Roboticinfo" should have a generic circuit to hand for this.

One could use power MOSFET devices or Solid Statate relays with no moving parts as an alternative ,they are an expensive method but fair better in terms of reliabilty, for the automobile can be a harsh enviroment for electronics to survive in.

As for software , everyone has thier own favourite

because this is for an automotive application the use of high resolution screens along with fiddly graphical user interfaces is something of an overkill, personally I would use something like QBII which allthough is a rather old DOS based package it will run inside win98 quite happily so one can write an easy to use compiled program that uses the numeric keypad or an up/down +select menu system that can call instructions for both media and control I/O ports.

 

[Roboticinfo]

reply

Well first I want to know the information I asked him first and depending on which one he gives me I will post up the schematic.

 

[Oznog]

When you say "ignition", do you mean to keep the car running or to run the starter?

The starter already has one relay, but the power requirements to even run the coil would require a transistor or relay to control from a digital port. This is dangerous because if you accidentally leave it on you will burn up the starter and possibly break off the engine's ring gear. But "remote starters" work just fine for that.

The "run" position is also somewhat dangerous since having the engine cut off on the road due to bad code or whatever (do you want your car to crash everytime your computer does?).

 

[dreamproject]

Components

Hi all,


I am using a Gigabyte Motherboard hosting a AMD 2400+ processor , the board's SMPS is powered by a 400w off-the-shelf inverter (1.3 A max.)(running on the car battery) . The Computer's VGA output is fed to a VGA-AV converter and then to a 8" LCD-TFT monitor (NecVox)(Accepts only AV input). The monitor is driven directly by the battery . All ports present in a normal desktop are available (USB , Parallel , Serial , Etc..) . My doubts are:


1. A warning on the inverter says " The output is not purely sinusoidal " . Is this cause for worry ?

2. When I start my car with the computer running , will it restart due to the voltage drop that occurs during a start ?

3. I have noticed waves on the monitor display , Is this due to the inverter being on the same line as the monitor or due to the inconsistencies in the refresh rates of the PC , VGA-AV converter and the Monitor ?

4. In reply to the query , I do not want to start the car with the computer but rather the Ignition (the position before start) . The starting , I would like it to be manual given the problems of isolating the computer from the heavy starting currents. I have found the ignition fuse , I intent to put the relay in series with this . Is this alright ?

Thanks for your time

 

[dreamproject]

addition

hI all,

I would like to add . The waves on the display become more prominent with the car running ....

 

[DirtyLude]

This will annoy you quickly.

1. You wont be able to start the car until your in car PC boots up.
2. If you have any problem with the in car PC, you can't start the car.
3. Cranking the engine sucks alot of current. Like you said, the PC is going to reset as soon as you start cranking, which means the relay on the starter is going to reset as soon as you start cranking; unless you somehow lock the relay in place until starting is completed.

 

[instruite]

Hi
Todays automobile have electronic control units inside the car for various purposes like engine control, transmission control, safety equipment control and many more
and all this units are designed using micrcontorllers but there is an interface circuit betwwen car parts and the micrcocntorller for example in case of a automatic transmission the transmission control unit inside the car controls different indications like P,N,R,D, etc. these are controlled by microcontroller inside the TCU but through an interface circuit which may consists of some transistor or lamp driver or similar circuit
So if you want to control the ignition with computer then you can use a relay in series with the ignition fuse but you will have to have a driver circuit between PC port and relay and also you will have to have a bypass circuit (like a manual switch) in parallel with the relay in case of some problem with car
Also while chosing the components keep in mind that components for industrial use and automotive use are differeent so use only automotive grade components.
As for your computer then there are many kind of surges on the power line of car so better use some stablizer circuit to power your computer