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Dreamer dreaming?

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forwardtocharis

New Member
Obviously I'm fairly new to electronics. I am familiar with a handful of components and some basic electrical theory.
I am trying to find a way to take six to twelve or so signals (on/off) and transmit them using a minimal number of connections (hopefully 2) to another location for output.
Specific application is as follows:
I want to have a handful of switches that I can put on the door of my truck and use them to control a handful of devices (specifically: lock, unlock, passenger window up, passenger window down, rear window up, rear window down, and have the option to add on). I already have added a handful of wires for the door lock actuator and speakers and I would like to avoid running 6+ additional wires (6 assumes I use the switches as ground switches and use the door as a ground).
I am more interested in learning through this than the quantity of work it will entail, so if there is a way, I'm interested in it.
Thanks!
 

dknguyen

Well-Known Member
Most Helpful Member
For it to be worth it, the devices are have to be centered around some point far away from the control panel. If the control panel is already at the center of everything, then there's no point- you might as well run the wire to each device directly from the control panel. It's like your brain, eyes, spine and limbs. Your limbs are centered around a location far away from your brain so the spine is a hub where they can connect and reach the brain through a single path. But your optic nerve just go straight to your brain- they don't go through your spine first. It's pointless since the nerve would be travelling away from the brain to connect to the spine, only to backtrack again back to the brain.

Also, your wording is misleading. Yes, you can merge multiple signalsand send them down a single line to split them up again. BUt you can't do this with power lines. If I understand you correctly, your control panel (with direct wiring) actually routes POWER through itself, not signals (which are data/information). The control panel does all the grunt work itself.

You can only merge data/control signals, not actual power lines. That means each device still needs it's own local power switch to connect the device to ground. Really...you are just moving the power switches from your control panel so they are next to each device. Instead, the control panel contains switches that send a data signal to toggle the power switches (which would now be electrically controlled switches like relays or transistors). So each device would need a relay/transistor and as well as electronics to interpret control panel signals and toggle the relay/transistor. The control panel doesn't actually route the power through itself anymore, instead it just sends commands on what to do. The control panel does no grunt work, instead it just tells the device's local electronically controlled power switch what to do, and the switch does all the grunt work.

It's a lot of work to save on a running few wires over such short distances.
 
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Mikebits

Well-Known Member
What you propose is much more involved than running a few wires. The mechanics would be a huge challenge.
 

Sceadwian

Banned
Unless you're planning on doing this professionally you won't learn much of anything from it except how much of a royal pain it is. Wiring a vehicle like that is never easy, 2, 12, or 20 isn't going be much harder than running the first pair. Keeping track of them all is an acquired skill that I would more call an art. Lots of colour coded wires and wire tags, and a good schematic to follow, you really don't wanna to free wire something that complicated.

Even if you could run the whole thing off three wires (Two for power one for a control signal) you'd require intelligent electronics at each node (failure point) and if something goes wrong you'll never sort it all out properly. As far as I know even the most modern luxury cars still use a central wiring point rather than 'inteligent' systems. Once you have all the wires run (a pair for each solenoid or motor plus whatever feedback signals are used) you at least have a single point to check for mixups.
 
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dknguyen

Well-Known Member
Most Helpful Member
Unless you're planning on doing this professionally you won't learn much of anything from it except how much of a royal pain it is. Wiring a vehicle like that is never easy, 2, 12, or 20 isn't going be much harder than running the first pair. Keeping track of them all is an acquired skill that I would more call an art. Lots of colour coded wires and wire tags, and a good schematic to follow, you really don't wanna to free wire something that complicated.

Even if you could run the whole thing off three wires (Two for power one for a control signal) you'd require intelligent electronics at each node (failure point) and if something goes wrong you'll never sort it all out properly. As far as I know even the most modern luxury cars still use a central wiring point rather than 'inteligent' systems. Once you have all the wires run (a pair for each solenoid or motor plus whatever feedback signals are used) you at least have a single point to check for mixups.
Planes also use direct wiring don't they? Less things to fail- not good in a plane!
 

Sceadwian

Banned
Most industrial devices do as well, there are buses used in many situations, but there are still a lot of separate wires. The 500thousand dollar automated hoist at my last job had a wiring harness as thick as my arm, many unused backups as well for replacement if a wire breaks. Half the cost of the installation was probably for the copper wire used =)
 
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kpatz

New Member
It would be a rather daunting DIY project, but you could do it with microcontrollers on a serial bus.

That said, many modern cars do use modules and a communications bus rather than hard wiring, in order to reduce the amount of wires needed. My Audi A4 does. Each door has a module which communicates with a central convenience module. Press a button to open a window, the module reading the switch sends a command to the module in the door containing the window to activate its window motor. Such communications allows for additional flexibility such as raising/lowering the windows from the keyless entry remote. It also allows you to read diagnostic codes via the OBD port from all the modules.
 

Sceadwian

Banned
Maybe for engine components kpatz, the windows/door locks and all that stuff is still usually hardwired. It's cheaper to have one main module control everything in the car than it is to have smart modules at each point in the car, what little it would save in wiring costs are lost in cost of the modules. They might do it on some luxury cars that have a LOT of features, but for simple power locks/windows there's really no point.
 

kpatz

New Member
Well, I can't speak for every car on the market, but my '02 Audi A4 does have modules in each door. Each module controls the window and lock in each door, along with sensing the window switch, door open/close sensing (to put the dome light on/alarm functionality), window pinch protection, auto up/down, lights on the door, etc. Imagine how complex a wiring job it is to do this without modules, especially for power windows, where the driver's door has switches for all the windows. Instead, the wiring harness going to the door only needs power, ground, and data lines. Also, speakers, if there are any in the doors.

This allows for things like opening/closing windows via remote, turning on footwell lights/door marker lights only for doors that are open, and having the instrument cluster warn of individual doors being ajar (instead of a single "door ajar" light). It can simplify diagnostics as well. Say that one door's power lock isn't working. With the hardwired setup, you'd have to trace wires all through the car to find the problem. With a module, you can pull a diagnostic code from the module that will tell you the problem (e.g. open/short on lock solenoid).

What's funny is, even my steering wheel has a module. Supposedly it's for steering wheels that have buttons in them (for radio control, manu-matic/tiptronic shifting, etc.). Even though my steering wheel is a basic one (no buttons), the module is still there.

As R&D costs are amortized and the cost of the modules drops, these features find themselves in cheaper cars as well. My friend's '01 Corvette has door modules too, and it's only a 2 door car.

Older cars, and cheaper newer cars probably do use a single module for everything.
 
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Sceadwian

Banned
I think it comes down to the 'fluff' features like the individual lights/warning indications you mentioned. Once it hits a certain complexity it's cheaper to do it with modules. Once you have the modules there are a ton of 'might as well' features you can add.
 

tcmtech

Banned
Most Helpful Member
I am good with electronics and vehicle electrical systems and I can tel you hate all that electronic crap they put in vehicles!:mad:

I have buddies that work at vehicle salvage yard and they say over 3/4 of the non wrecked vehicles they get are there just because someone had enough electrical system failures to justify dumping the car for scrap!
To me thats sick. What could have been a good reliable vehicle gets dumped because some jackass engineer thought it would be a great Idea to put modules and gobs of wire every where and use them to control stuff that ultimately proves to be more of a driving distraction than anything! :mad:
I hate trouble shooting crappy designs. I want a door switch that turns on the interior light without going through a computer. I want a blinker that blinks with out going through a computer, I want a horn that actual sounds like I am angry when I us it and does not go through a computer, I want a simple window wiper control that doe not go through a computer.

We have a 1959 international dump truck that is in all original condition and everything electrical still works! It has 5 fuses and each controls something that is important and nothing else!:)
They built vehicles for how many decades and electrical failure was never a big problem. The vehicles wore out long before the electrical system did!
Now the electrical system is the number one root cause of warranty work! WTF! :mad:
Doesn't that say something? :mad:
I love electronics but get that crap out of my vehicals. :mad:
 
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