Before going on with this, please note that the Focus's PATS system will need to be by-passed somehow...possibly with a module.
For my setup, I'm thinking about locating the PATS pickup sensor to the bottom of my seat, or center console, allowing me to keep the key in my pocket and keep the added security of the system in tact. Of course this will not allow me to use the remote to start my car! But anyways...
I've been doing a lot of thinking about push button starters, but I wanted something a little more sophisticated than a couple of switches and a manual button...so I came up with this.
Basically, I just need a couple of relays along with the Viper alarm, and I'll be able to double click to start and drive away!
For this to work this way, you'll need a DEI alarm starter...I'm going to use a Viper 791 in this example. But I think any remote starter can be made to work...
I think all DEI starter/alarms setups have a 'lead' wire to trigger the remote starter...all you do is tap into this with your push button.
The Viper will engage a latching relay with an auxillary channel output (Thanks Goldse!), Allen Bradley part #700-HJD32Z12, turning the car to full 'run' at the same time it starts the car (apart from just powering the fuel pump, ECU, etc..).
I will be using an Allen Bradley 800E push button, with a black metal gaurded operator, with a green lens. These buttons (well most, if not all 800 series models) allow multiple switch cartridges for whatever your config requires. The push button, setup with two cartridges, is capable of sending a ground trigger to the Viper, with one cartridge, which it needs to run the start program AND a positive signal to the latch relay (to open the circuit) using the other cartridge. Why is this?? Read on :)
Here is what happends...
To start the car, you double-click the button. Two ground pulses are sent to the Viper from one of the cartridges. It checks that all the safeties are met, and fires up the engine. At the same time it is pressed, the push button also send a + signal using the other cartridge, to the latch relay for the 'run' circuit to OPEN it. But because of the timing, the Viper completes (closes) the latch circuit AFTER this, thereby switching the car to 'run'. Now when you push the brake to disengage the Vipers 'run' relay, the car is already in 'run,' so now you can drive away...
When you want to turn OFF the engine, push the start button once more to open the latch again, breaking the 'run' circuit, killing the engine...
This is very similar to Toyota/Lexus type push button starters, and really adds a lot of sophistication and 'wow!' to the setup, opposed to the S2000/NASCAR type starter, where you manually hold the button...BORING!
Now it gets even better...
If I need just the accessory, or 'run' function (depending on how you want to hook it up) WITHOUT running the engine, the start button is also hooked into a electronic timing relay...it's set to look for a delay signal (not a pulse) before it works. If it doesn't see a delay hold on the trigger, it's bypassed.
For accessory, you must hold down the start button for 2 seconds (or whatever amount of time you like...it's programable), and it powers up the acc. circuit. Hold it 2 seconds again, and it powers down. The Viper remote start circuitry also ignores this type of input, as it is looking for only two consecutive pulses, within 3 seconds I believe, to start.
(THIS part of the design I'm still working on, as I'm learning as I go...but I'm pretty sure Allen-Bradley has a electronic, programmable timing relay that suits this function. I've requested a suitable part number from various manufacturers that's needed for this setup...I'm just waiting to hear back. I'll post up a part number as soon as I know.)
If you just want a start function, this part of the design can be totally left out, or added later.
Also, the button I'm using, an AB 800E, will be designed to illuminate green when the car unlocks and the engine is off (thru the dome light, or better yet, from the Vipers door unlock relay). This is to signify that the engine is off, and is ready to be started. Once started, the button will illuminate red to signify that it is running or the acc. mode is engaged.
All of this is simply powered from the relays...basically a two-colour LED in the illumination cartridge of the button. You could even go three coloured, and use a different colour for the accessory function if you wish!
Here is what my button looks like, except for the lens colour...
Okay, so...I just made the schematic while learning SmartDraw...nice program! It's just a basic drawing to give you an idea of the setup.
I'll do another Focus specific schematic with properly labeled and colour wiring when I have time (or after I have this tested in my car)
So if you have any questions, or if I seemed to of missed something, let me know :)
For the latch relay, technically, it isn't accurate in the drawing, as it needs an 'on' trigger as well as a seperate 'off' trigger...so I connected it up and added a ground.
I am using Allen Bradley components thruout, as I think they offer outstanding function and reliability...but are quite costly!