(I have called it this for the benifit of the non-techies)
Previously we have discussed EMI and its effect on battery drain. But there is another topic that could be even more interesting.
Ways of reducing the complexity of the car wiring have been sought such as by (ideally) using a single pair of wires to supply everything and then switching things on and off by sending an appropriate code of pulses down the wire pair. Thus each headlamp etc., would have an electronic switch on the back of it and would respond only to its own special code words, for on, off and dip.
As you can imagine such a scheme has enormous scope for some very funny effects in the presence of interference! Anyone know if it is in use yet?
Did I mis-interpret the news item I heard on the Pug that catches fire because it sounded to me like it might be using something like this.
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I think I mentioned this type of communication between different parts. I read it was possible to to do this but research is still ongoing. MB apparently were doing more research than anyone else into it. I forget what it was called but the idea was to do away with wiring altogether. some call it pie in the sky but as bluetooth is doing very well I have reason to think it will be poss for all comunications between ECU and sensors take place as bluetooth operates within small areas/metres.and is interference free. could be the way to go remains to be seen?
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I think that you will find Multiplex wiring has been used by Citroen/Peugot in the the 806 and Berlingo for a couple of years now. It may be used in C2 3 &5 but I do not know for sure.
The concept is not new, I recall going to a presentation by the Lucas research group in 1968 or 69 where the whole principle was outined basically as used now! However in those days the semiconductor industry was struggling to make cheap devices that could cope reliably with the somewhat nasty enviroment experienced in a car. (That also includes the workshop staff efforts at fault finding).
Adding a towbar socket takes on a whole knew world of problems!
I have just done a very quick Internet search, it appears that some VWs, the Neon (since 1999) and the Ford Scorpio (when did that stop production?) have elements of Multiplex wiring included.
pmh (was peter)
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You mean multiplex wiring or the "can bus"?
Yes its in use now. Most new cars are a mixture of standard and bus technologies. The new BMW's (5 and 7) are full multiplex /can bus technologies some of it run by "MS windows automotive v2" i understand.
And yes - funny things can happen. Ask the US navy who decided that sailors were expensive so built the latest AEGIS anti missile ship to be run by Windows.(NT i think). Engines/steering/defence systems etc........Of course it was towed back into harbour.....
You can always tell if your car has a bus technology. The lights come on seconds after you turn the switch. Very annoying when all you want is a quick flash...
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Using a serial interface in a car is not exactly rocket science. You have a control unit that takes the drivers instructions , i.e. light on off, fog lights wipers etc etc, and transmits a device ID and a command word, i.e. Rear Lights, ON, a unit in the rear of the vehicle with that ID receives the command, acts on it and sends back a status, Lights On , with this the Bus Controller continues to check the status of all devices. Ideally these electronic switch should be solid state but a 12 volt only system is a bit prohibitive but the newer design of vehicle with 36/42 volt systems are going solid state.
12 volt systems, due to voltage drop and the higher current have been prohibited by the cost against the cheapness of relays with very little voltage drop. However with a 12V system you have to distribute power to these remote controllers and although the rear lights are not too bad, min 15 amps per corner, the front corners with head lights spots, day lights, flashers etc etc, calls for some heavy gauge wiring to be used along side the twisted pair differential serial bus control wires.
I very doubt that Bluetooth type wireless technology will ever come into the control of a car arena as these type systems, although can be made to be fault tolerate would be much more prone to external interference and mutual interference between adjacent vehicles never mind the unjustifiable cost. It is going to be a lot more expensive to replace a busted part that is for sure. I’m happy with a relay box and a few kilos of wire. To think that a future generation of car will have an electric oil pump, good ideal as the pressure is up before you start it and goes off when the oil has cooled down is great but to have a radio signal turn it on and off doesn’t grab me at all and I’m an electronics engineer in the radar industry, trust me I’m a doctor !! Regards Peter
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Just like the government have rendered our mobile phones useless on New year's Eve twice in recent years, and then issued false press releases saying everyone got "Network Busy" messages because so many people were texting and saying Happy New Year, they will sooner than you think be able to disable most cars en masse, in fact you may have seen the paraphernalia being installed at the sides of the roads in preparation. It will be like your car is not yours anymore. :o(
e.g. If there was a protest like the countryside alliance one or the anti war people's they would make sure you couldn't get there.
So buy a series I or II Land Rover diesel.
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Huh, where'd you get the idea that the government disables mobile phones at new year from?
As with any wireless digital system there will be an associated bit error rate. This can be calculated by using a good propagation and noise model and then improved with some coding and error correction techniques, unfortunately the more you want to improve it the more expensive it gets. Because of the small distances involved though I should think the the transmitted power from the master and slave units should be sufficient to avoid most problems. Of course if you knew the frequency that the car was using and had a high enough power transmitter you could jam it........
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Wireless digital in a car is not practical from a cost base or environment (ie in a car) base. As has been said, once voltages in cars are increased (and hence current goes down) then full multiplex wiring will be the norm. Shielded bus cables will ensure minimum interference.
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I think that is taking the conspiracy theory a bit far, but in any case its a political subject not a motoring one.
Neither is it suitable for the Technical Matters Forum.
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"Just like the government have rendered our mobile phones useless on New year's Eve twice in recent years, and then issued false press releases saying everyone got "Network Busy" messages because so many people"
What a load of old tripe! never heard such rubbish. Why would they want to do that at that time anyway!
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"in fact you may have seen the paraphernalia being installed at the sides of the roads in preparation."
Nope not seen it what does it look like? We are all dying to know.
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