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-   -   engine start / stop button question (https://www.fuelly.com/forums/f9/engine-start-stop-button-question-5452.html)

lunarhighway 07-19-2007 07:20 AM


It might be dangerous for someone untrained in your vehicle to be in it if they can activate the starter without the key
they'd also be able to turn off the ignition without the key... far more scary... but it'll be in a recess anyway so accidental or delibirate activation is less likely. and i'll most likely be so proud when i get this working i'll tell everyone what it is :D

most people are affraight to drive my car anyway, they seem to think any 20 year old car must be a wreck, most suspect my tape grillblock is there to keep the car together... lol

anyway, i hope to be able to get all the goodys i'll need this friday so i can have a look at things over the weekend.

JanGeo 07-19-2007 07:33 AM

I think you miss the point of the start button - it is smart - it will automatically start the engine and turn off the starter motor once it starts, all while either just tapping the button or holding it in.

lunarhighway 07-19-2007 08:29 AM


Originally Posted by JanGeo (Post 64366)
I think you miss the point of the start button - it is smart - it will automatically start the engine and turn off the starter motor once it starts, all while either just tapping the button or holding it in.

in your car maybe, but i know that when i turn the key one notch forward with the engine on there's a nasty screaching noise comming fom under the hood... had that a couple of times while i thought i was EOC ing but the engine was still on because i turned the ignition back on to soon while it was still spinning... doing a keystart than did not sound so well. that said my car usually starts pretty well especially when it's warm so a small nudge against te switch should be enough to fire it up again. this car's 20 years old so i should think some things have evolved. although i like the solid straightforward construction of it

Gary Palmer 07-19-2007 09:35 AM

Lunarhighway: I think the point JanGeo was making might have been missed. Your correct that if you turn the starter switch the notch foward, the starter engages and grinds teeth on the flywheel. I think the switch JanGeo is talking about is electrically disabled, when the car is running, so that even if you toggle the switch, the starter won't engage. It makes it so the starter will only engage, if the car is not running, which is a little different behavior than the key switch.

As far as your cutoff and so forth go, you don't need to use a relay unless your using it to actually switch the power to a device that uses a lot of power. For example you could use a switch to control the starter relay, but you would not want to use a switch to power the starter.

If you do use switchs, I strongly recommend you put a 0.01 micro farad capacitor across the switch contact connections. It will help keep the switch contact points from arcing and burning themselves out. You can run it without the capacitors, but the switch will wear out, fairly quickly and you'll have to replace it.

I have a switch on my car, for cutting off the power to the injectors. It works fine, although I get a cel when I use it. I haven't gotten a start switch wired in, yet, although it is planned.

My only warning is that if you have the kill switch, like I do, it is easy for someone, like my kids, to fiddle around playing driving in the car and fliping the switch, without me knowing it. I spent a good deal of time tracking down why I couldn't get the blinkin car to restart.

lunarhighway 07-19-2007 03:24 PM

sorry JanGeo if i came across rude. i may not always understand everything correctly, the system you describe would be more elegant than what i'm planning to build.
but all i need is something that replicates the engine on / engine off function of the key in a more accessible position. i don't need anything else unless safety dicates it.

as far as acidently opperating the system by passengers goes...i'll let you all in on a little secret. it so happens that directly behind my gear shifter there's a little ash tray/garbage bin, that folds open . it looks like it's never been used, and i don't smoke, but it's ideally placed to put down a sigaret and free your hand to shift the gears. there's even a tiny light in it when the main lights are on.... perfect spot for a switch i'd say. when it's not needed i can just stow it and noone will notice it's there or be able to interfere with it

i initially thought i'd need 2 buttons but i figure this switch combined with one relay can do the trick.
it will always return to the center neutral position and won't do anything without the key so i think i'm safe there as far as kid's interfearance goes (there probably won't be any kids for the next few years so that helps too ;) )
i can set it up so that "up" is the starter and "down" is the ignition cutoff, same as what i do with the key now.

thanx for the tip on the capacitors Gary Palmer , i didn't realise sparks would be that much of an issue. i assume that all wires leading from the key swith are just part of the 12V system and drive relays to power the starter and the ignition opperating on a higher voltage but 12V should be enough to make some nasty little sparks i guess. should i put a capasitor across the relay as i assume there's still a mechanical switch in there?

rh77 07-19-2007 03:34 PM

good thread
As an automatic driver, I'd love to have one attached to the shifter so engine kill can be done in neutral with one hand on the selector, and same for restart and "D" engagement.

If it's in a "public place" in the car, maybe you could wire it up with a lockout or bypass at the flip of a switch, so it doesn't get monkeyed-with when you don't want it to.

But yeah, even with a key-start system, I've ground on the starter with the engine running. It happens most right after cold start when the RPMs are up and I fail to take a quick glance of the tach to see that the engine was still rotating and fired back up at key-on. It's easy to be hyper-vigilant with EOC and reading other traffic, and not on instrumentation :rolleyes: .


skewbe 07-19-2007 04:10 PM

I like a golfcart type approach (it just isn't on the top of my priorities at the moment)

IF the clutch is all the way in
AND the throttle is significantly off idle
AND the ignition is on
AND the engine is not running
THEN start the engine (needs to know when to stop starting also)

skip the clutch bit on an automatic maybe.

lunarhighway 07-20-2007 01:10 AM

i quess i should know this since i've studdiet electronics for 2 years but most of what i (should) have learned there is shamefully gathering dust somewhere in the back of my mind.

does anyone know how to calculate what capacity the capacitors should be that go over the switches, i did some brief research on the subject and it seems to be a very good idea to install them so i'll give it a go. yet i'm not sure what capacitors to get though (i'll probably get them today after work), does it matter much what capacity they are or do i have a certain margin 0,01µF seems fairly low ? if i understand the way they work correctly it shouldn't matter that much. also what's the importance of their voltage rating is that max voltage, if so anything above 12v should do rihght, as they all seem to be on the high side.

anyway any help will be greatly appreciated, capacitors are interesting but i do know they tend to blow up (elcos at least) when you attach them the wrong way round. needless to say lot's of these things where “accidently” blown up in class. i'm not intending to get elco's as i don't need their capacity.

lunarhighway 07-27-2007 11:17 AM

I've got the goods!!! :D
most of them i should think:

as mentioned it my LED question thread i finally decided to go for a dual button system.i was considdering a single paddle swich opperation, wich i could still make.

i'm building this into my fold out garbage bin, but since i want to be able to stow the bin i can't have anything projecting beyond the edges so buttons where more handy, plus the LED's will add a cool effect, and aid at night.

the people in the shop where very helpfull, when i got the switches the guy mentioned i'd need resistors asked me what voltage i'd use and simply grabed two resistors from a bin. according to the color code they're 562 ohm, 5% tolerance, that's about what i'd calculated... should give me about 18mA so that looks fine.

i also got a little buzzer wich will act as a powersaving device by alerting me when i've left my headligths on. apparently this was an option 20 yeas ago.
my car does turn of the headlights automaticly, but only after about 2 hours...by draining the battery. :rolleyes:
here's a some relays i found in the attic... they're probably pretty old, but they still work fine and the left one is even so kind to tell you what's inside! how thoughtfull. i plan to use this as a breaker swich for the ignition, it will be driven by the stop switch.... guess wich color i'll use for that one.

here's the garbage bin (wich i doubt the privious owner even found by the look of it!...it looks factory fresh on the inside...i feel a bit sorry to drill holes trough it) i'll fabricate some sort of front plate to accept the buttons.

stay tuned for more pictures of this stuf being put together, silly questions, and perhaps some explosions...

skewbe 07-27-2007 05:19 PM

Might I suggest putting the switches on the stick shift? It's a very "handy" place.


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