Electronic Relays and Push Button Ignitions.

[Liv]

Okay, I'm in search of advice again.... hoping one of you have your electric engineering degrees....

Alright, question one....
1) Wheres a good place to order 12v relays?
2) Is the best way to delay the activation of a NO Relay by using a timer relay, or is there something else I can use? I only need to delay it for second or so?
3) Is there a "amount" of time or a time limit to latching relays where they might cycle? Or can they sustain an entire 1-2 second pulse?

That's it for now.....

[A Person]

Digikey is a good place to order electronics online but you could probably find what you need from scavenging old electronics

If you want to implement a delay there are various solutions. One would be to use a transistor to drive the relay and control the transistor with a capacitor C (100uF), by varying the resistor R1 (500 - 10K), the capacitor will take longer to come up to voltage and switch on the transistor. R2 should be a high value (1M) and is there to discharge the capacitor to reset the circuit.

Another way is to use a micro controller such as the Atmel mega 8 which you can program to do whatever yu want, but there is a learning threshold and you need to buy the stuff to get started.

One more would be to use a 555 timer.

[Liv]

It's funny, one of my first thoughts was using a cap. I wondered if it could delay the current long enough....

What... I'm leaning towards... unless someone argues it's stupid.... is using a A/C delay relay like off a GM... I found them online for about $7.00.... and while it doesn't say how long it's timed for, I'm guessing it's a few second while you start the engine which is perfect.....

I'm trying to do this cheap as eventurally I'd like to add RFID to the circuit...

This is what I came up with....

This stuff isn't easy for me at all, so there may be an easier option, I just can't think of how to do with without adding in a secondary kill switch.... which seems so faux pas.....

[A Person]

The capacitor isn't 'delaying the current' it's controlling the voltage on the input to the transistor. When the capacitor is 'empty' it's voltage is 0v. As it slowly charges (at a rate determined by R1) the voltage increases until the transistor switches on.

I believe the delay for an AC Delay Relay can be anywhere from 8 seconds to 1 minute. You could pick one up from a junk yard.

What are you actually trying to do?

[BecauseHeLives]

My guess is that Liv is installing a push button ignition in her car.


Either that or she's planning on taking a moving van by the local federal building.

[Liv]

Push button start.... the iginition actuator in one of the cars went bad, and for this car you have to pull the steering column, and disasemble or replace... (like $500 that I don't have, right now)

figured I'd upgrade instead....

I was just going to wire the starter to a switch and call it a day, but I figured it shouldn't be too hard to make it like the new factory deals with a few relays....

so this is what I came up with after many hours of trying to figure out how to stop the starter from spinning on the second press....

Here's what I'm planning...

Switch...
Latching Relay
Timer relay
NC Relay

Then, down the road, if I'd win the lotto I could add an RFID relay before the switch...

[Liv]

Either that or she's planning on taking a moving van by the local federal building.

LOL... suppose it does look a bit shady at first, doesn't it....

[A Person]

I don't understand your problem. The starter motor relay is in the engine compartment and is presumabky accessible. Why do you want a latching relay or delay circuit? If you connect that pretty switch to the starter relay that should be all you need. The switch will not work without a relay as it's only 10amp, a starter motor is around 100 amp

[Liv]

I don't understand your problem. The starter motor relay is in the engine compartment and is presumably accessible. Why do you want a latching relay or delay circuit? If you connect that pretty switch to the starter relay that should be all you need. The switch will not work without a relay as it's only 10amp, a starter motor is around 100 amp

No I'm assuming that this will still terminate going through the factory relay to turn the starter.... The purpose of this relay scheme is basically to be able to not only "start" the vehicle but to "kill" the vehicle on the same momentary switch, without having the kids say "Oh pretty shiny button" and press it while I'm driving down the road at 3500RPM....

If I thought of this right, then the only "risk" time would be in that 'delay' period on the relay which I could illuminate with an led, and should present a fairly small window as most people don't turn the vehicle "on/off" repeatedly... (plus I will be educating operators).


@BHL .... in a Lightning:
http://www.youtube.com/watch?v=rEH0ruL1v7g

[A Person]

You are mixing up the starting and ignition systems. The starter should only work when the ignition is on but using one push button switch for both is (as you point out) dangerous and it means you cannot have the ignition on without the engine running. The logic is difficult to implement

1 Push ignition on
2 Push and hold - run starter
3 push ignition off

Is the steering column switch completely kaput? If so how about buying a generic ignition/starter switch (e.g. a boat one) and patching it in
http://cgi.ebay.com/ebaymotors/GENERIC- ... 75001r5337
or
http://cgi.ebay.com/Mercury-Style-Ignit ... 286.c0.m14

[Liv]

I've used the "universal" tumblers before, but I was just leaning for a little more "bling" to be honest...

The switch is fine, it's the actuator that's bad.... that's how we're driving it right now... but it's just a mechanical lever switch with a plastic rod that goes through the center of the steering column....

My first instinct was to merely install a race type starter button from back in the days... where it's basically like you're suggesting... a single starter momentary switch and a kill, or aux switch.... that's when I discovered there's more "nicer" aftermarket versions out there... but they all seem to lack the more complicated "on/off" system unless you buy one of the "smart" systems for $500... which defeats the purpose here....

I don't know why I would need the car in "run" without the engine running???? (It's earlier, maybe I'm missing something.) The ACC mode will be wired to a separate switch...

[A Person]

I think what you are calling the actuator rod is the the interlock to prevent you starting the car in drive and/or the brake on, the ignition circuit is still active. Presumably you've found a way to bypass the interlock already

If the column switch is still working then you can just take the starter wire to a big red button and turn things on and off with the column key and start the engine with the big red button.

Big Red Button

starter.gif (9.96 KiB) Viewed 4350 times

Isn't that enough 'bling'? Bearing in mind that no matter how much you pimp the thing, no one is going to ask you if it's been done by Foose.

I don't know why I would need the car in "run" without the engine running

One reason is if you have power windows - they usually only work if the IGN circuit is on. Other things that often only work with IGN on are the wipers, headlights. Some diagnostics can only be done with the IGN on.

[Liv]

Do they not make stepping relays anymore?

[A Person]

Yes.

You seem to like making things difficult (and more expensive) for yourself.

Have fun

[Liv]

Ha... my second grade teacher said the same thing after I did 4x the necessary homework...

[Liv]

Well I ended up going your route and keeping it simple....

Works good... though I hate the blue... it was on closeout...

For anyone else who is interested in the ignition switch wiring harness for the Taurus... this helped a lot:

[Liv]

Okay A.P.

Need electronics help....

So if I'm understanding this right, wiring two resistors in parallel will reduce the overall resistance. ???

Let's say I have a circuit that currently is 400 ohms right now. Let's say it's putting out 4 volts at 400 ohms.

By adding a 300 ohm resister in parallel with it, the resistance should go to 171ish? Right? Does that also mean the voltage will go up? Assuming say a 5 volt input?

[A Person]

Yes, wiring resistor in parallel lowers the resistance. The formula is 1/((1/R1)+(1/R2)+ ... (1/Rn))
So the net resistance of a 300 and 400 ohm resistors in parallel is 1/((1/300)+(1/400)) = 171 ohm

I don't know what you mean by 'putting out 4V'. There is a voltage drop accross a resistor which is related to the resistance and current by the formula V=I x R (Voltage = Current x Resistance)


Let's take example 1.

circuit1.gif (3.2 KiB) Viewed 2675 times

If the battery is producing 5v, you have a 400 ohm resistor and a voltage drop accross the resistor of 4v, this means the voltage drop across the load is 1v. We need to know what is the current in the circuit and what is the resistance of the load. Then we can work out what will happen when we add the second resistor.

V = i x R
4= i x 400
i = 4/400 = 1/100 = 0.01 amp

So the current in the circuit is 0.01 amps.

Calculate the resistance of the load
V=i x R
1=1/100 x R
R= 100

Now we add the second resistor in parallel, the total resistance of the circuit is now 171 +100 = 271 ohms.

circuit2.gif (3.91 KiB) Viewed 2675 times

V=i x R,
5 = i x 271
i = 5/271
i = 0.01845

The voltage drop across the two resistors is
V = i x R
V = 0.01845 x 171 = 3.16 volts

And the voltage drop across the 100 ohm load
V = 0.01845 x 100 = 1.84
which could also be calculated by subtracting 3.16 from 5v

Hope that helps ...

[Liv]

Yes!,

I've got a thermister which I need to signal a slightly lower resistance than it's putting out, and I'm trying to figure a way to do so without going to far.

I've got to get the ohm meter out when I get a chance and see what's going on.... but I'm tackling it in my mind right now.

[A Person]

Thermistors usually have a resistance in the k ohms at freezing temp, dropping to hundreds of ohms at temps over 100C, your parallel resistor will tend to swamp the thermistor effect.

thermistor.jpg (19.26 KiB) Viewed 2644 times

Since you're not measuring resistance but volts, you can always modify the input voltage with a regulator. they're cheap and simple

http://www.national.com/mpf/LM/LM317.html#Overview