Help needed with transistors

I have been trying to use a transistor, connected to the unused boot release wire of the security system and also connected to the ignition wires, to allow the car to be started remotely when the boot release button is pressed.  When I could not get it to work, I did some tests to try to work out was was happening:

When the transistor's emitter and collector pins are connected to the ignition wires, and a 1.5 v battery is brought into contact with the base pin of the transistor, the engine starts.

Also, when the base pin of the transistor is connected to the boot release wire and a 1.5v battery and multimeter are connected in series to the emitter and collecter pins of the transistor, the multimeter shows that current is flowing through the circuit each time the boot release button is pressed.

However, when the transistor's emitter and collector pins are connected to the ignition wires and the base is connected to the boot release wire, nothing happens when the boot release  button is pressed.

So the transistor seems to work fine when two different batteries are used, yet when it is just the car battery being used as the power source, there are problems.

What am I doing wrong?

Any help would be much appreciated.

Thanks,

Tim.

what type of transistor are you using??? Is it rated for 12V, and how many amps is it rated for????,

Why are you using a transistor, wouldn't a relay be better suited for this???

Typically transistors are used in control logic situations as a type of switch that is controllable, etc.....

Craig..

A relay is what I tried to use first, but the voltage on the boot release wire is too low to activate it (about 1 volt).  Are there relays available that can be activated by a voltage this low?

I am using a power transistor, but I don't know what it is rated at.  Although I do know that it can handle the 12 volts as it worked fine when I activated it manually with a battery instead of the boot release wire.

Tim.

I am not familiar with boot release wires...I imagine they have different types of switches that you could find on digikey that would be more suited to your application, I would have to look myself, I am not sure of one off the top of my head.   As far as the transistor....now explain to me exactly how you hooked it up, how you tested in (in the car).  if you can provide a picture it will help as well.....

Also, give me more info on the boot release, and I will try to analyize your problem.

Craig

The boot release wire was installed when the security system was installed.  The people that installed it showed me a number of unused wires under the dash.  Some of these are for connecting central locking, and another is for opening the boot via the remote on my keyring, however, as my boot is mechanical, not electronic, this boot release wire is unused and is not connected to anything. Using a multimeter I have found that when one of the buttons on the keyring remote is pressed, about 1 volt is sent down the boot release wire.

Here is a diagram of how I wired everything up:

And a diagram of one of the tests I did.  When I did this test, the engine started:

This was another test I did.  When the boot release button on the switch was pressed, the multimeter showed current flowed through the circuit:

umm, question, how are you going to remote start your car by hooking to the ignition wire???? You need to interface the starter wire.    I was not sure what you were trying to do....but you need more than  a relay or transistor, since you have to have a timer, since you don't want to rev your starter for to long, .... I do not have a lot experience in remote starter setups, (at least installing the commerically available ones), but maybe Jeff or someone will post and explain more about how the remote starter works for all of us.  I assume it applies a voltage to the starter wire for a period of 3 secs or 2 secs or something to turn over the car (ie simulating the effect of turning the key).   Then from there your car should be started, but that is just a hunch.  If the boot release only turns on for 1sec, i doubt that will be enough to turn over your car, so you would need some sort of interfacing device, like a microcontroller or something to set up the delay...just a suggestion!

Sorry I could not help more...... 

Tim,  I am guessing that you are attempting to use a PNP transistor (if I am reading your diagrams correctly).  This transistor type requires a negative bias between the base and emitter to cause the transistor to conduct.   In other words, the base must have a more negative voltage than the emitter to cause current to flow from collector to emitter.  But even more of a problem is that cited by the post before me- the duration of this circuit to operate.  crroush correctly suggests that the starter circuit is not momentary.  I know Bulldog has a starter circuit aftermarket kit that can either operate for a set amount of time or can sense engine rpms from a tachometer "sense" line.  Don't know about any other models....

So you have a couple of problems here.  I suggest that you consider replacing the security system, or supplementing it with a remote starter system, one that is designed to interface more easily to your car's circuitry.