I am trying to develop a multiplex project for an special car to operate the lights, door locks, windows, etc.
I am a noob with only some ancient knowledge of electrical wiring, and I want to know if I can do this reasonably. I know there is an available aftermarket setup but it is extremely expensive.
What do you mean by "a multiplex project"? Do you mean you want to network devices together rather than run power wires from a central place out to each component (light, lock, window lifter, etc)?
Multiplex means sending diffrent signals down the same line. We normally talk of time division multiplex but there is also frequency division multiplex.
What is it exactly you want to do onthe car, what you describe I don't recognise as multiplexing.
Does the special car already have lights doors windows hooked up to a control panel or are you making this car and nothing is hooked up yet?
What do you mean ancient knowledge of electrical wiring, like Baghdad battery? 
johnwasser:
What do you mean by "a multiplex project"? Do you mean you want to network devices together rather than run power wires from a central place out to each component (light, lock, window lifter, etc)?
Yes.
liudr:
Does the special car already have lights doors windows hooked up to a control panel or are you making this car and nothing is hooked up yet?What do you mean ancient knowledge of electrical wiring, like Baghdad battery?
The car has everything hooked up with normal wiring, ie 2 wires with switches going to each item (+12v and Ground).
My ancient knowledge goes back to normal automotive wiring, with switches, relays, etc. No computer based setup's, no transistors, etc.
OK, if you want to use arduino to control these accessories, you can use relays to open and close the circuit in place of the original buttons or switches. I am no expert in cars but I suspect those switches are also driving relays to turn on and off those power-hunger devices so you may be able to replace the switches with simple transistors. Arduino can drive these transistor to turn on and off the devices with their original relays.
liudr:
OK, if you want to use arduino to control these accessories, you can use relays to open and close the circuit in place of the original buttons or switches. I am no expert in cars but I suspect those switches are also driving relays to turn on and off those power-hunger devices so you may be able to replace the switches with simple transistors. Arduino can drive these transistor to turn on and off the devices with their original relays.
No, I am looking for a setup to replace the present wiring in the event of a re-wiring of the car. Which arduino would I start with?
A basic arduino UNO will be able to easily control about 18 devices. If you have good knowledge how a switch turns on a light, you can replace it with arduino pin and transistor (or relay). How many devices do you want to control?
liudr:
A basic arduino UNO will be able to easily control about 18 devices. If you have good knowledge how a switch turns on a light, you can replace it with arduino pin and transistor (or relay). How many devices do you want to control?
2 tail lights ,2 headlights Hi/Low, 2 brake lights, 4 turn signals, 2 door locks, 2 windows (up and down), possibly 2 trunk latches.
I could breadboard the circuit to see how it works, using a couple of solenoids and window motors to duplicate the door latches, and windows.
New question: How is the arduino programed? Will I need a compiler?
(This should help you if someone hasn't already posted a reply)
The arduino has it's own software, that compiles it before you upload it to the board. You can download the latest software here: http://arduino.cc/en/Main/Software Download the software for your computer, MAC, windows, linux, whatever you have. If you have a windows 7 computer, then the boards should automatically install the drivers and setup a COM port for you, if you have windows XP, it is a little more work. For a MAC, I personally don't know, I don't have a MAC.
Now when you install the software and drivers, make sure you choose the board you have and the serial port it is assigned to, under the Tools menu. To get started, there are examples you can try, under the File menu => Examples. I suggest start with LED blink and move on to the next one.
You should also get some basic parts to test with,some LEDs, resistors, relays, buttons, switches, and possibly some servos and motors, but those will require a few more parts.
If you have any programing knowledge, know that this software is open source.
Yes you need a compiler but it is free and open source. Just purchase an arduino uno and maybe some LEDs and resistors. You can use them to represent your devices and get the program logic correct before moving on to solenoid and the actual car.
Grumpy_Mike:
Multiplex means sending diffrent signals down the same line. We normally talk of time division multiplex but there is also frequency division multiplex.What is it exactly you want to do onthe car, what you describe I don't recognise as multiplexing.
Late model automobiles use what they call "multiplexing" to eliminate conventional wiring, where a +12v wire has to go through a switch and then to every individual device. This has always resulted in large bundles of wiring harnesses. The use of "multiplexing" allows the use of one +12v wire encircling the complete car (or at least a section of the car), and turning on or off the individual components by means of a signal by a light weight twisted pair. In some cases the signal can also be returned to diagnose failure of the device such as a burned out bulb.
That is what I am trying to do.
Darth,
Thanks for pointing out what multiplex means in automobiles. A lot of us, myself included, don't know about this. So I googled it and found someone's thesis about this topic and read the first 2 chapters.
http://innovexpo.itee.uq.edu.au/1999/thesis/orourke/thesis.pdf
Hopefully your project will not have to deal with multiplexing, at least at this stage. According to multiplexing, any control is hooked up to this bus and maybe a central node decides whether a instrument should turn on. If you don't have to create such a control that uses the bus, but only attempt to replicate pushing of buttons with arduino, your project will be easier, I think.