Odd question... (Electronics)

[450Nick]

I'm trying to think of a way that I can have my starter circuit determine whether or not the engine is running so that the starter button will not operate unless the engine is off. I currently have it set so it monitors oil pressure, but if the car starts and then stalls (such as on a cold morning), the oil pressure doesn't die off quickly enough so it will not return to operation for quite a few seconds. Is there another way of driving this circuit? The reason being that I'm sacking off the key start as it keeps knocking my knee and am going with a starter circuit controlled by the immobiliser and a button instead... Just need a good safeguard to stop the button working once the engine is running... Any ideas?

[eliot]

A relay that is fed from the alternator somehow?
ETA - in fact from the charge light!

Edited by eliot on Monday 1st June 07:14

[450Nick]

eliot said:

A relay that is fed from the alternator somehow?
ETA - in fact from the charge light!

Edited by eliot on Monday 1st June 07:14

Cunning! How does this charge light actually work? I presume its the battery symbol on the speedo (TVR Chimaera). Does it activate when the voltage rises above battery voltage and therefore starts charging the battery? And if so, what kind of feed is it? Switched earth or 12v signal?

Thanks!

[stevieturbo]

Charge light is grounded to illuminate.


Another idea would be, not to push the starter button once the engine is started. It's free, requires no trickery, and is fvery very easy.

Edited by stevieturbo on Monday 1st June 12:20

[Ant.]

Nick, aren't there any user configurable outputs on the Emerald that can be used?

Its a shame the change light output only goes down to 2k rpm, as you could possible use that to drive a relay when the revs reach 500 rpm say.

Might be worth asking Karl.

[450Nick]

stevieturbo said:

Charge light is grounded to illuminate.


Another idea would be, not to push the starter button once the engine is started. It's free, requires no trickery, and is fvery very easy.

Edited by stevieturbo on Monday 1st June 12:20

Well this is the ideal situation, but sods law says that someone (probably my father) will push it when I'm not looking and blow up my starter motor. For this reason, I'm really don't want to temp fate so I'll stick some safeguard in...

Ant, I've thought about the Emerald, but it doesn't look like there is anything workable there. I've looked at the VTEC switching function which can output a signal when the engine revs pass a certain point, but it also relies on throttle position which I don't want. I'll ask Karl...

How fast does a starter motor spin at roughly?

[spend]

You could use the timed heated mirror circuit, just a few cunning conditions that make that active. Or the fuel pump to defeat the starter ~ but its better for the 'inert' state to be normal IMHO.

[annodomini2]

Is there an available output available on the ECU to set high/low above a certain engine rpm?

You could drive a relay to enable the starter motor circuit.

[stevieturbo]

If its only a safegarud against pressing while the engine is running, as opposed to holding it too long whilst starting.

Then using either an oil pressure switch or alt charge light would be very easy.


Every engine is different with regards speed. Datalog your own to find out whislt cranking.

Probably 150-300rpm though

[450Nick]

There is a VTEC switch function which allows a signal to be raised when a certain engine speed and throttle position is met. Currently it switches above about 4k revs and 30% throttle. This would be ideal if I can get it to ignore the throttle part.. Perhaps if I set both to 0 it will work - I'll ask Emerald. If so, I can have this trigger the relay shut out when the engine speed gets about 500rpm... I currently have it running using this circuit:

http://www.chimaerapages.com/img/res_starterbutton...

[Zad]

Admittedly I'm in a different position, but I would take the tacho feed, filter it to provide an analogue DC value and then run it through an op-amp comparator.

[eliot]

My understanding of the charge light is that one side of the bulb is fed by 12v from the battery - the other side goes to the alternator windings. When the alternator isn't running, that winding is ultimately a very long piece of wire to ground - hence the bulb lights up. When the alternator is running - its outputting 12v, so the bulb has +12v either side of it - and therefore goes out.
It would require a diode to work correctly, but you may have an issue where the relay drops the feed to the starter button before the engine has fully 'caught'.
Given you have an Emerald - i would find a way of using that instead - or just dont bother.
I have a toggle on the dash for my starter (ign barrel u/s) - and have only ever hit it once whilst the engine is running - doesnt sound good - but no terminal damage either.

[Mr2Mike]

I've got this cunning arrangement of a keyswitch mounted on the steering column. Passengers can't reach it, and once you have released the key from the start position, you have to go back to off before you can start again. It also serves the dual function of the steering lock, how neat is that?

[stevieturbo]

Mr2Mike said:

I've got this cunning arrangement of a keyswitch mounted on the steering column. Passengers can't reach it, and once you have released the key from the start position, you have to go back to off before you can start again. It also serves the dual function of the steering lock, how neat is that?

Sounds cool...

Is this an aftermarket kit ? I quite fancy an arrangement like that for mine. Sounds almost foolproof :P

You should maybe market it yourself

[450Nick]

Mr2Mike said:

I've got this cunning arrangement of a keyswitch mounted on the steering column. Passengers can't reach it, and once you have released the key from the start position, you have to go back to off before you can start again. It also serves the dual function of the steering lock, how neat is that?

Yes alright if it ain't broke don't fix it and all that... I just don't like the fact that in its current location it is forever punishing my knee (I'm tall), and to make things simpler overall, I'd rather just sack it off completely and have the whole car controlled, by just my immobiliser fob. So when its unlocked, I can hit a toggle for ignition on or off, and a button to start. Simples

[Steve_D]

Sounds like way too much effort for something so unnecessary.

If you press the button by mistake it makes a nasty noise and you don't do it again.

Now that's simples.

Steve

[InRong Ghia]

I would have said the earlier comment of the fuel pump is the easiest. Does the Emerald fully control this, including the initial "pressurise" when the ignition is turned on? If it does not do that, then use that side of it, otherwise worst case, you have to wait till it has stopped, but from your description of what you want, I am guessing that this means you cannot start the car for a period of less time than it takes you to open the door and get in :-) Or were you thinking of moving the basic ignition?

That is always the other option, just put the basic key structure somewhere else out of the way.... Not as cool as a starter button I know...

[450Nick]

Yes but I already have the starter button plugged in so this is just as easy!

Spoke to Emerald today, if I set both throttle conditions to 0, then the VTEC switch works purely on rpm and earths a pin when it activates, so it will be perfect for driving the circuit. Thanks for the input guys, I'll get this factored in when I do some more wiring under the dash next week...

[Ant.]

450Nick said:

Yes but I already have the starter button plugged in so this is just as easy!

Spoke to Emerald today, if I set both throttle conditions to 0, then the VTEC switch works purely on rpm and earths a pin when it activates, so it will be perfect for driving the circuit. Thanks for the input guys, I'll get this factored in when I do some more wiring under the dash next week...

Nice one, another feature of the Emerald then!