Car Engine start button questions

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Aaroona

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#77542 17-Feb-2011 22:26

My new car is currently getting certified etc and I am wanting to install a starter button.

I just have a few questions though;

How am I able to stop the button from burning out the starter motor if the button is pressed while the car is running? A mate of mine has just wired up a start button in his car, but his will burn out the starter motor if its pressed while his car is running - a potential problem if you have people in your car who are sticky fingers and like to fiddle.

I know that BMW and some Audi's have this feature, but I am wondering if there is an easy/aftermarket/cheapish (~200) way of doing this.

So thats really my other question; what parts would i need, and where would I get them.

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#440938 17-Feb-2011 22:42

What the??

Don't press the button while the engine is running or if your that worried about it cut the power to the solenoid on the starter motor while the engine is running.

You don't put the 12V and the current required to turn over the starter motor thru the starter button

John

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tonyhughes

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#440941 17-Feb-2011 22:51

No difference here to turning the key to the starter position, would your passengers do that?

Get new passengers... I have a 4 year old who respects what I tell him he can and cant touch in my work car, vs being allowed to in our own car.

Aaroona

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#440942 17-Feb-2011 22:58

Tonyhughes: Thanks for the lack of help, Much appreciated.

John: in regards to your comment there about cutting the power to the solenoid. How would I go about doing that? Im a little timid when it comes to playing with stuff in the car, but wouldn't mind giving this a go as long as I'm pointed in the right direction.

Aaroona

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#440943 17-Feb-2011 23:05

Just to clarify;

I want to stop the button from working WHEN the engine is running.

so say im driving down the road and the button is pressed, I don't want that button to do a thing (idealy I would like it to stop the engine, but that opens a whole nother can of worms)

So basically, the button won't work again till I next go to start the car (after the car has been turned off)

nate

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#440951 17-Feb-2011 23:20

johnr: Don't press the button while the engine is running or if your that worried about it cut the power to the solenoid on the starter motor while the engine is running.

tonyhughes: No difference here to turning the key to the starter position, would your passengers do that?

Get new passengers... I have a 4 year old who respects what I tell him he can and cant touch in my work car, vs being allowed to in our own car.

Sometimes the most obvious answer is the best.

ArtooDetoo

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#440953 17-Feb-2011 23:22

Aaroona:

So thats really my other question; what parts would i need, and where would I get them.

I'm no electrician, but I would think a simple solenoid would do what you're asking.

In the solenoid's 'relaxed' state, the contacts are bridged, completing a path to the live terminal of the starter motor's own solenoid. That path is then broken only by your starter button which, when pressed, completes the circuit to the starter motor and as long as the button is depressed, the starter will turn.

But... as soon as the engine fires, the charging circuit takes over the battery's task of supplying energy, so you can tap into that to feed power into your solenoid, energising it, which in turn pulls the bridge away from the contacts of your starter button circuit which then breaks that circuit and no matter how much you hold the starter button down, the circuit will remain broken by the solenoid.

The solenoid will only relax again and bridge the contacts of your starter circuit if the charging circuit is no longer producing sufficient voltage - that is, when the engine stops.

Maybe $60 for a solenoid, wire, fuse carriers (one for the starting circuit and one for the solenoid powering circuit), some spade terminals and solder.

In summary, your solenoid completes your starting circuit except for your start button. Push the button and power flows to the starter. As soon as the engine starts, the charging circuit (from the alternator and rectifier) fires up and the power from this circuit energises your solenoid, dragging the contact bridge away from the starting circuit, breaking that circuit and rendering the start button non-functioning.

As soon as the engine stops, however, the charging circuit voltage goes to 0 and allows the solenoid to return to its relaxed state, once again bridging the break in your starter circuit. Which means that when you push the start button, power will again flow to the starter. Bear in mind that the power for your start circuit should come from the ignition switch terminal that currently (no pun intended) is one position before the spring loaded key position.

Hope that is food for thought. And sorry about the length of this response.

Cheers,
R2D2

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freitasm

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#440954 17-Feb-2011 23:23

If you are worried about it, why not just keep using a key? Starting the engine is something that is done once in every trip. It's not like a heavy lifting or anything like that.

If you can't tell people to not touch the button, then just don't make the button available...

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Aaroona

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#440955 17-Feb-2011 23:24

I mean no disrespect to you guys because a couple of you have helped me in the past, but I have asked a question. One that I would like answered sufficiently.

If you don't genuinely want to help answer my question, then don't bother posting. That simple.

johnr

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#440956 17-Feb-2011 23:25

Simple don't press the button when engine is running!

I don't get it do you drive down the road and turn the ignition key on any other car?

Maybe when the engine is running you can send 3000 volts to the starter button so you are not tempted to press it.

Aaroona

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#440959 17-Feb-2011 23:29

Thank you ArtooDetoo for your reply! That actually is making a bit of sense to me. I will read over it again tomorrow when I'm not so tired and mention it to my friend. We're currently brainstorming a couple of ideas and I think this could be a winner.

We're also toying with the idea of the button only working when the clutch is pressed, or the handbrake is applied.

Clutch won't apply to me, as I have a clutchless manual, but to my mate is still possible.

Thanks again for your reply. Very helpful :)

ArtooDetoo

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#440960 17-Feb-2011 23:30

Aaroona: Thank you ArtooDetoo for your reply! That actually is making a bit of sense to me. I will read over it again tomorrow when I'm not so tired and mention it to my friend. We're currently brainstorming a couple of ideas and I think this could be a winner.

We're also toying with the idea of the button only working when the clutch is pressed, or the handbrake is applied.

Clutch won't apply to me, as I have a clutchless manual, but to my mate is still possible.

Thanks again for your reply. Very helpful :)

No worries.

Let us know how it works out.

Cheers,
R2D2

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vfxguynz

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#440962 17-Feb-2011 23:37

Hello aaron :P

I've just installed a push to start engine button in my car. It works great, except the car's starter motor will self-destruct if you press the button after the car's started.

Luckily, in the place I have mounted the switch, no one *should* press the button.

I have thought about wiring in a relay that enables/disables the button depending on whether or not the handbrake is up/down (Enabling when up, disabling when down). This could even be a switch that is activated physically by the clutch, handbrake etc.

Anyway, that'll be another day. Check out the install pic's at my blog http://audicarpc.wordpress.com/2011/02/17/update-15-engine-start-button-install/

Stu

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#440969 18-Feb-2011 00:21

Keep in mind if you're not too savvy around the electrical system in your car and for some reason it all ends in a charred mess, you may have no insurance cover as it wasn't done by a suitably qualified auto electrician. They use any excuse to get out of paying.

Other than that, have fun!

Hiamie

353 posts

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#440976 18-Feb-2011 01:56

The simplist solution that I can think of, is to install a second safety switch in series with the normal starter switch. This second safety switch could be mounted near the pedals, so that the drivers foot MUST depress and hold the safety switch first before the normal starter switch becomes active.

riahon

946 posts

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#440983 18-Feb-2011 05:05

I have been out of the workshop for many years but I am struggling to get my head around this.

When a key is turned, the solenoid turns on the starter motor and the starter gear engages with the engines flywheel to turn the engine over. If the engine is running and you turn the key then the starter motor tries to engage the gear to the flywheel but because it is doing several thousands revs it cant engage, result a terrible graunching sound but no engagement so the starter doesn't turn.

If you are using a button, then I am envisioning a spring loaded button which will only activate the solenoid when it is depressed. The engine starts and you remove your finger. If the car is running and someone were to 'accidentally' press the button I don't see how the starter would engage any differently to using a key.

What sort of car is it?

You could go super rad and have some sort of shield that slides back over the button like a jetfighter where you flick aside a plate, press the button and then is slides back over. That would be cool.

If you also placed the starter button on the right hand side of the steering wheel then the only one that can accidentally press it would be the driver.

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