Ok so i got my button in! but i need someone to verify that this will work...

Red box is a 12V source that gives 9-14V when the car is on and Running (W on ecu, 5th pin on 2nd harness)



push it once with clutch in should start the car... push it again should turn the car off

push switch is a momentary switch - it does not stay locked in position

all relays are in their open positions

This post has been edited by pittfirefighter: Dec 27, 2009 - 10:18 PM

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No, it's not quite right. You have the ACC and IGN lines tied together at the top and once the button is pressed the first time, they are additionally tied to the battery. Perhaps some diodes? Additionally, you probably want some diodes across the relay coils to prevent back-emf and probably use latching relays rather than have the coils always energised for the latching function.

Are you assuming that when the battery is disconnected from IGN and ACC, pin 5 will go to ground? Oterwise, I can't tell how a second press kills the car.

For safety's sake, I'd suggest either two presses within one second should be needed to turn the car on/off or alternatively a 1 second long press.

One final consideration - if you don't already have one, fit an immobiliser and position the coil wherever you are going to put your keys (eg next to a cubby hole). They you can just throw the keys in the cubby hole when you jump in the car, but without the keys in the cubby hole someone else won't be able to start and steal your car.

D.I.Y Immobiliser
Immobiliser

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1. ACC and IGN should be tied together (IGN is not START, it is live when the key is usually at ON) and therefore taken straight to battery when the car is running... diodes are a good suggestion - not quite sure how latching relays work...

2. no pin 5 will not ground - if it was to ground, then the battery would short circuit... pin 5 is open creating an open circuit - open circuit would create no power flow therefore IGN and ACC don't get any power and the car shuts off

3. that will be determined depending on how well the car starts

4. already have an immobiliser worked out... i want to get the starting function down first before adding that in

ok just researched latching relays... seems i learn something new everyday this will greatly cut down on how complicated the diagram is... will update shortly

EDIT: just wanted to make this clear also... this diagram is not only for starting the vehicle but keeping it running as well and turning it off all from one button.... there will be no key and no lock cylinder, there will be an immobliser type feature added to the ECU

This post has been edited by pittfirefighter: Dec 29, 2009 - 6:40 AM

updated diagram

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Okay, so what we have here is (numbering the relays from top to bottom and left to right):

Push and hold the push button: energisies the colis for relay #1 (latching relay) and #2.

Current flows from the posivie terminal of the battery through the switch for relay #2, the switch for relay #3, through the clutch switch (when the clutch is fully depressed) and through the coil for relay #4.

Th current flowing through the coil of relay #4 in turn closes the switch for relay #4, which allows current to flow from the +ve terminal of the battery, through switch of relay #4 to the starter motor. The starter motor turns, causing the engine to crank and start, at which point the red box (pin 5 of the ECU) goes from open circuit state to +ve voltage.

Current flows from pin 5 of the ECU through the coil of relay #3, breaking the circuit at relay #3 switch, which in turn stops the current flowing through the coil of relay #4, causing the switch at relay #4 to open and the starter motor to stop turning.

At this point, relay #1 is latched (switch is closed), relay #2 is energised (switch is closed), relay #3 is energised (switch is open), relay #4 is un-energised (switch is open), ACC, IGN and pin 5 are all +ve.

Releasing the push switch causes relay #2 to be un-energised (swich opens), which has no effect.

Pressing the push switch a second time causes relay #2 to energise (switch closes), which has no effect, and the ratchet-and-cam locking relay #1 to switch states (so that the switch is in the open position again).

This causes the ACC and IGN lines to become open circuit and presumably causes pin 5 of the ECU to go open circuit also.
With IGN open circuit, the engine and most of the electrical systems will shut down.

At this point, relay #1 is unlatched (switch is open), relay #2 is energised (switch is closed), relay #3 is un-energised (switch is closed), relay #4 is un-energised (switch is open), ACC, IGN and pin5 are all open circuit.

There is a minor problem here, in that if one were now to depress the clutch, the starter motor would crank. This could be solved by powering the left-side of the relay #2 switch from IGN rather than from +ve battery.

Releasing the push switch causes relay #2 to be un-energised (swich opens), which has no effect. At this point everything is back to its initial state.

One other advantage with using the double-press to start the engine (and having a timeout function) is that then a single press could toggle te ACC circuit on and off, which is exactly the same functionality on the factory-fitted Toyota start buttons.

thank you very much... the idea was that relay #4, in theory, would keep the car from cranking when it was on (including turning off)... i will be able to now eliminate relay #4 and run the starter relay off of the ign wire as recommended...

the idea is that the clutch out will be ACC/IGN mode while clutch in would go to START

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Much simpler, but does mean that one could over-crank the starter by keeping the push button pressed for too long on startup, or crank the starter momentarily if the clutch was depressed while pushing the start/stop button to stop the car.

This feels like the kind of problem that automotive accessory manufacturers would have already solved. It is fun to design and build such circuits - but I wonder if there isn't something already out in the market that would do what you want and is affordable.

yes one could over crank the starter by holding the button down... but it would not be any different then holding the key to the furthest position... there will not be enough time in shutdown to both engage the starter and crank it

they are not even close to being affordable nor workable with this celica nor stylish...

i am implementing the nissan push start button (best looking in my opinion) with keyless use

my total will be less than $100

This post has been edited by pittfirefighter: Dec 29, 2009 - 11:35 AM

Why not just have an off and on button and make your immobilizer start the car?

that takes away from the fun of a push start! the immobilizer is going to be the type that unlocks the doors when you're near them as well as activates when you're inside the car.... same as most keyless vehicles now