engifineer

The key will have to be pretty close to the ign switch to deactivate the stock immobilizer hollywood. I am not sure how close, but I dont think in your pocket would do it, which is why I mention securing it behind the dash near the switch, or in the column. I would only consider this if you have a very good alarm with its own immobilzer based off a card or transponder of some sort.

For the ignition switch, I would have to look at what they are connected to. I am guessing there is one for ACC, one for IGN and one for start. And there should be one for batt power as well.

xIxAMxHOLLYWOODx

Thats my plan, is to use the key as the "card" for the immobilizer. that way I can run Acc. and Ign. on separate toggle switches, then have the push button for starting (and never have to insert the key). But I dont want just anyone to be able to hop in the car and start it up (hence the immobilizer). I have scion security, but Im not interested in running it through the alarm system.

zzzBrett

I got the ebay alarm listed earlier and it should be coming in this week some time. As soon as i get it installed, i'll start with the suggestions listed, and post questions / updates as i go along.

Brett

zzzBrett

OK!

I got the alarm installed, and it works as expected.

Engifineer, I think my next step is building the latch circuit you designed. What parts are required for building this?

You start by saying I need two normally open contacts, but then you say i need one NO contact, and one NC contact, so i assume you meant i'm going to need one of each.
From your writeup, i came up with:

1 Project Box
1 Normally Open Momentary Push Button
1 Normally Closed Momentary Push Button
1 Relay (Type? Link?)

Are these parts that i can get at my local radioshack?
How do these links look:
Project Box:
http://www.radioshack.com/product/in...entPage=search
Automotive Relay:
http://www.radioshack.com/product/in...entPage=search

And to further clarify, am I going to need two latch circuits? One for the engine start and one for ACC power?


Thanks again for all of your help,
Brett

STNC

iTrader: (1)

So as you walk towards the car it unlocks?

zzzBrett

Yes, it unarms the alarm and unlocks the driver door. When I walk away, I hear it chirp signaling the alarm is armed and doors are locked.

STNC

iTrader: (1)

What alarm was it? Links? How easy was it to install? What do they key fobs look like?

zzzBrett

K9 Sombra:
http://item.express.ebay.com/Consume...mdZExpressItem

Pictures in listing.
$105 to install @ circuit city

STNC

iTrader: (1)

You should do a video of it in action? Does the stock key still work?

zzzBrett

Yes, stock key still works.
I'll work on all that after getting my main goal working: Push button start!

STNC

iTrader: (1)

All i know is that the tC has 2 starter relays you need to tap

Bozuzu

watching. . .

engifineer

For the latching portion, you just need one normally open contact on the relay to latch it. You need a normally closed pushbutton to unlatch it. As for the other contacts, you will just need a set for everything you need to control. If some items draw much less than the capacity rating of each contact set on the relay, you may tie a couple of things to them. For instance, if you are powering two devices that pull 1A each, and your relay contacts are rated for 5A, then you can just tie 12V to one side and both devices to the other.

For the relays, you can use a standard automotive relay. The pushbuttons from radio shack should work as well. Just be sure to buy parts with the proper capacity so you dont burn anything up.

andino

interesting...tempting to do this too lol. good luck with your project. keep us updated please

zzzBrett

Ok i'll try out the 30A relay at radioshack, hopefullly that'll work. I'm not sure how to determine the exact amperage i'd need.

But for the relay, the standard automotive relay i linked to is a SPST relay - is this the correct kind for me? I'm not even sure what prongs on the relay i hook up each wire to, so i guess i'll buy it, take a picture, and use some labels and post it to determine where each goes.

Brett

zzzBrett

Sorry for the lack of picture quality, but all i have is my cell phone.

Here is a relay i picked up at radioshack (item # 275-226)



Looking on the schematics on the back of the packaging, here are what each of the prongs are for:

1. "12v IN"
2. "on/off switch"
3. "12v OUT"
4. "ground"

OK..
Now my question is how to i make this into a latch circuit?

Here is the latch circuit picture description mentioned previously:



Do the numbers above match up correctly with the numbers on the latch circuit schematic?

If so, what are the two remaining prongs pictured on the latch circuit? I'm beginning to think i should have gotten a SPDT relay?


Thanks again for all the help,
Brett

engifineer

The thing with that relay is that you only have one set of contacts, which is used to make the latch. You can tie off of them to run something, but I personally recommend having one set of normally open contacts in the relay for the latch and another to control the device.

The contact for the on/off is what controls the relay, the ground is the ground side of that. Those two make up the coil in my diagram, and if the relay has a diagram on it or the package, it will have a coiled line representing it. The 12V in and 12V out represent each side of a normally open contact.

engifineer

To clarify a bit, if you want a latching relay that controls one device (or more devices that can be switched at the same time, and do not combine to overload the current rating if the contacts) you need a Double Pole Single Throw switch with both sets of contacts in a normally open configuration. One set will be used for the latch, one will be used to power the load.

zzzBrett

Ok.
Sorry this is taking me so long to understand. Before this, i've never even used a relay. So bottom line is I shouldn't use this relay? I should use a DPST relay instead. Once i get a DPST relay, i still am not sure where each of the wires will hook in to my car.

What i think will happen:
-When first momentary (NO) button [POWER ON] is pressed, the latch circuit will be engaged. Thus feeding 12v to any/all devices attached (IGN/ACC)
-The second momentary (NC) button [ENGINE STOP] will open the circuit, thus disengaging the entire latch circuit. Power to all attached devices will be cut.


To start my car:

-There will be a third (NO) momentary push button [ENGINE START] wired to the engine start wires. Pushing this will start the car.

To stop my car:
-I will simply press the (NC) button [ENGINE STOP] on the latch circuit, cutting power to IGN (is this way what usually happens when i turn my key? just cutting power won't hurt anything?)


When I walk away, my car doors lock. The 12v pulse will be also wired to the [ENGINE STOP] button, cutting IGN power in case I forgot to push it.



Now that all of that is outlined, my 'to-buy' list:
-DPST relay
-Buttons

Searching radioshack online, it seems that they do not have ANY dpst 12v relays. I'll check home depot / lowes tomorrow. Could you recommend any other places to purchase them?


Thanks,
Brett

engifineer

you can wire the momentary ON button to both the latch and the start wiring so you can just hold it down to start, and it will latch the ignition. I am thinking that since you still have the clutch safety in place, if you want to just turn acc on only, you simply dont press the clutch and press the on button, which will latch the relay. The relay will feed the ign/acc. If you want to start the car, you press the clutch and hold the button until it starts.

The downside of this is that you always have ign powered when acc is.

The other method is do do as you say, but you need two latch circuits. One latches when you press the button for the acc and one latches when you start the car (powering the ign circuit to keep the car running).

A third, and more tricky option, is to build a circuit that will allow one press of the on button to trigger acc, a second press to power ign (if you need to read the gauges for example) and a third press and hold will start the car. :D I could create a schematic to lay it out, but it may be a while since I am moving and really busy for a few weeks aftterward.

If you know which method you want to use to make it all work, I can help you figure it out. Sorry to sound confusing, but there is a bit of logic to get it all to work correctly. But it will be nice when it is done!