re: failed car ignition

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

At 07:51 AM 7/9/2003 -0600, you wrote:
>Original poster: "Black Moon by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><black_moons-at-hotmail-dot-com>
>
>60 to 100khz? gez, everyone and there grandmas smps uses that freqency!
>And if they don't, they probley use one lower that has a harmonic of that 
>freqency (Smps = squarewave = tons of noise all over)
>CRT monitors operate around that freqency with a sawtooth wave, (horzontal 
>scan) so they can probley cross over and interfer.. Lots of stuff is 
>probley pertty close to that freqency, what a horrable freqency to pick

On the other hand, it's also a good frequency band to choose for inductive 
coupling... You have to couple both a signal and power to the key so that 
it can operate.  This is fairly standard RFID technology.  As far as 
interference goes, it's all a matter of design.

 From an interference standpoint, you're mostly worried about magnetic 
fields and the loops which radiate the EMI are quite small, and the field 
drops off quite quickly (because it's the net field from a magnetic 
dipole.. get very far away and, in a rough and ready conceptual sense, the 
field from the N end of the dipole is exactly as strong as the field from 
the S end of the dipole, and it neatly cancels.




>>This is quite interesting.. The RF link from engine control unit (ECU) to 
>>transponder in the ignition key is a low frequency inductive link (60-100 
>>kHz or so..).. The coupling is usually done by a coil that surrounds the 
>>ignition key lock.  All the smarts is in the ECU (so you can't defeat it 
>>by cutting some wire in the steering column).
>>
>>It is not out of the question that a TC might radiate enough energy to 
>>couple into this system and confuse it enough that the ECU and key can't 
>>run their protocol.
>>
>>
>>At 07:40 AM 7/8/2003 -0600, you wrote:
>>>Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
>>><IanHelixsp-at-aol-dot-com>
>>>
>>>Hi all
>>>
>>>My previous occupation was as a technician, working for Audi/VW (18yrs).
>>>During the last few years we had more and more complaints about vehicles 
>>>refusing
>>>to start when parked in certain locations! After some time and processes of
>>>elimination I realised that this was due to r.f. interference from radio
>>>transmitters i.e. near the local police h.q. etc. (Also in the same 
>>>areas, cases of
>>>continuous false alarms from vehicle security systems) I have never had an
>>>instance of a vehicle breaking down due to this, just failing to start. I
>>>attributed this to the vehicle immobiliser system, which usually takes 
>>>the form of a
>>>radio transponder within the ignition key. The E.C.U. is programmed in a 
>>>'fail
>>>safe' mode to prevent the vehicle from breaking down once started and 
>>>running.
>>>In other words the immobiliser's digital out-put is ignored once the engine
>>>is running.
>>>
>>>Cheers,
>>>Ian D. Liverpool U.K.