Author Topic: Ground noise  (Read 7390 times)

Offline yanmar

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Ground noise
« on: September 09, 2012, 07:56:02 am »
When i build up electronic det can discovered  strong electrical noise comming from the idle soleniod valve. When disconected all is OK. The oscilloscope shows it very good(about 300mV peaks). It is hard to listen the engine as when release the trottle my ears blow up. I've tried to disconect the doide N...01  and to use the stepper motor from the original control of my 1.8t, but noise is there. I cannot find info how is organised the idle control on the PCB.
Any help?  ???


Offline yanmar

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Re: Ground noise
« Reply #1 on: September 12, 2012, 07:51:18 am »
quick update if someone can give me an idea:
the noise appears at "0" trottle only and when the serial  cable is connected to my laptop

Offline GintsK

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Re: Ground noise
« Reply #2 on: September 12, 2012, 09:07:18 am »
May be just feed your detcans directly from battery?

Gints

Offline yanmar

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Re: Ground noise
« Reply #3 on: September 13, 2012, 08:42:22 pm »
I have preamp for the knock sensors, which is with 9V battery. From there the signal goes straight to the laptop and i record the session and listen  real time. Later I compare the log with the audio file to find the exact moments when knocking.

Offline Benzmac16v

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Re: Ground noise
« Reply #4 on: September 15, 2012, 08:09:36 am »
You probably have a ground loop issue.  Are the det cans interfacing with your VEMS ecu or the car battery at all (other than through the laptop)?  Is your laptop plugged into the wall? Are your "mics" electrically isolated from the block?  If they are grounded to the block that will create a ground loop as well.  You can check that with a multimeter, just disconnect the mic from anything else that could be grounded back to the block (i.e. your pre-amp circuit).

You may want to take a look at the frequency of the noise, compare it to other signals from VEMS.  I would check it against your coil firing frequency as well as anything that may show up on your TPS signal (I don't know if you can look at the raw values or not, but that would be best, rather than looking at TPS as a %).

Grounds are a bitch, and must be done right.  I had a custom crank position sensor made and the guy grounded it to both the wiring harness and the housing of the sensor.  So I had a massive ground loop and I would get a trigger error only when my coils fired.

Jim

1985 Mercedes-Benz 190E 2.3-16v - VEMSv3.3 1.1.92

MemberWiki: http://www.vems.hu/wiki/index.php?page=MembersPage%2FBenzmacx

Offline yanmar

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Re: Ground noise
« Reply #5 on: February 03, 2013, 10:38:09 pm »
just to reprort where was may problem: The ground cable was not 6mm2. When I connected additional cable all problems disappeared.