Date: Tue, 14 Jul 1998 11:13:03 -0500
Reply-To: Darrell Boehler <midwesty@TAOS.MIDWEST.NET>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: Darrell Boehler <midwesty@TAOS.MIDWEST.NET>
Subject: Re: Darrell Boehler's digifant tool
Content-Type: text/plain; charset="iso-8859-1"
-----Original Message-----
From: Darrell Boehler <midwesty@taos.midwest.net>
To: Dave Bayer <bayer@SYBASE.COM>
Date: Tuesday, July 14, 1998 10:19 AM
Subject: Re: Darrell Boehler's digifant tool
------------------------
Hi Dave,
Thanks for your interest in the digifant tool. I shared your concerns
as I was building the digifant tool. Lets face it there is a lot of
electronic noise generated by the ignition system . Flat wire cables are
designed such that electronic noise tends to cancel out as it crosses the
many conductors of the cable. On the digifant connector many pins are ground
or voltage ( not signals) and they tend to shunt and reduce the noise that
will be picked up by signal wires within the cable. The tool is normally
inside the van where noise is at a low level. If one suspects the tool is
generating problems the tool could be unplugged from the digifant ECU
leaving just the short flat cable. This cable could be further insulated
from electronic noise by wrapping it with aluminum foil that is grounded.
As a side note never roll up flat cables into a nice neat coil, always use
them unrolled. This is especially true of pc ide, scsi etc flat cables. I
have not noticed any noise or strange problems with the digifant tool in
about a month of driving. The digifant ECU must have been built to tolerate
a bit of noise. Most all the wires in the engine compartment that
eventually connect to the digifant are plain wires just hanging out where
there is much electronic noise.
It may also be possible to make the tool using a shielded pc serial /
modem cable, however pin 1 of a shielded modem cable is the shield, for the
digifant we would need to reconfigure the connector. Again Dave thanks for
your interest and bringing forth your concern about noise. I'm sure if you
write about it many more must have concerns in the back of their minds.
Darrell
-----Original Message-----
>From: Dave Bayer <bayer@SYBASE.COM>
>To: Vanagon@VANAGON.COM <Vanagon@VANAGON.COM>
>Date: Monday, July 13, 1998 4:56 PM
>Subject: Re: Darrell Boehler's digifant tool
>
>
>>>| Basically, what Darrell does is
>>>| solder a cable with a inside the ecu, with a female connector on the
>other
>>>| end. He then constructs a box with a male connector which plugs to the
>>>| aforementioned female connector. The box contains electronics
>supporting a
>>>| series of led's to check various engine functions and a pin layout that
>>>| allow one to check the oxygen sensor, afm, and both temperature sensors
>>>| with a multimeter- and do it while the engine is running! Detailed
>>>| descriptions of the electronics are on Darrell's website at
>>>| http://taos.midwest.net/vw.
>>
>> The one thing that keeps popping into my head on this is
>introducing
>>RF noise into the system. Is there anyway to shield a flat ribbon cable so
>>that it doesn't act like a big antenna? I'm not worried about the test
>>equipment destroying the ECU (though I suppose it should be said that one
>>needs to be a little careful with the test leads), but I am a little
>worried
>>that the van could shut down everytime I drive under a set of high tension
>>lines...
>>
>>dave
>>
>
| 
