noise filtering

http://jbperf.com/dual_VR/index.html

noise filtering

Postby phongshader » Tue Jun 26, 2012 12:39 pm

I just received your dual vr board 2and hooked it up. I'm wondering how to filter out some of the false triggers I'm getting:
false trigger.jpg
false trigger.jpg (194.4 KiB) Viewed 5501 times

The top two captures are with the cop leads plugged into your 4 channel board, the bottom left is without the leads plugged in and the bottom right is the crank trigger.
here are some logs of attempted starts
MS2 extra 3.2.3, dual vr board, 4 channel board, sequential cop
Attachments
2012-06-26_09.21.41.msq
(83.58 KiB) Downloaded 175 times
2012-06-26_08.59.51zip.msl
change the extension to zip to extract
(206.29 KiB) Downloaded 170 times
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Re: noise filtering

Postby jbelanger » Tue Jun 26, 2012 1:16 pm

If I understand correctly, you have noise if the ignition is working and no noise when it is not. The first thing to establish is if you have resistor spark plugs; if not, this is the first thing to correct because it is a known generator of noise.

If that's not the issue, how do you have the COPs and the 4-channel board connected? And how is the cam trigger (which I assume is where you see noise but you don't mention) connected to the dual VR board? Also, your scope traces don't seem to show noise on the cam trigger input (if that is what the top 2 traces are) but that is very hard to say because the trace don't have a high enough gain (not enough V per division) and also don't have enough precision (needs to show a smaller time frame). There might well be noise on the input but the traces don't show it and/or the scope can't see it (what's the scope max frequency?).

Jean
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Re: noise filtering

Postby phongshader » Tue Jun 26, 2012 2:35 pm

They are resistor plugs: NGK R PTRF5 11. The cops are connected to the 4 channel board through the DB15 plug as laid out in your instructions. The board is attached to the lid of the MS case, all 3 grounds are used, and wire leads to the cops, from 28" to 41" on 16 gauge gxl wire. CAS is connected to the dual vr board on 20 gauge shielded wire to the MS relay box on s1 and s2 pins (25, 27) and yes it's the cas that's the problem.
false trigger01.jpg
false trigger01.jpg (178.87 KiB) Viewed 5493 times

The scope can go to 0.1uS.
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Re: noise filtering

Postby jbelanger » Tue Jun 26, 2012 3:02 pm

What exactly is connected to VR+ and VR-? Is VR- connected to ground? You don't want VR- to be connected to ground either at the dual VR board or at the CAS. Also, you can put a 1K shunt resistor between VR+ and VR-: this should help with noise.

The problem might be that the MAX9926 is too sensitive for your setup. It has adaptive thresholds but if the signal is too slow, it doesn't help because there is a time out. If you can and it's not already done, use shielded wires to your CAS. Or at least twist the 2 wires together such that you have a twisted pair.

Jean
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Re: noise filtering

Postby phongshader » Tue Jun 26, 2012 3:57 pm

The VR- is only connected to - out on the cas to -in on the dual vr board, not grounded anywhere else. The VR+ is only connected to + out on the cas to +in on the dual vr board. The connection is a 20 gauge 2con shielded wire from the cas to the screw block on the MS relay, shield grounded on the engine block, one end only.
Too sensitive...:x I'll try the resistor.
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Re: noise filtering

Postby jbelanger » Tue Jun 26, 2012 4:19 pm

What is between the relay board and the MS? You should bypass the relay board and connect the shielded wires directly to the MS. Even if you have shielded wires between the relay board and the MS, there will still be a possibility that noise is induced at the relay board.

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Re: noise filtering

Postby phongshader » Wed Jun 27, 2012 11:32 am

After you telling me that the board may be too sensitive...I tried out shunt resistors from 470-10k no improvement. At this point I switched back to a lm1815 (Zeal) conditioner so I guess this topic isn't relevant here any more but if you would, I'd like to hear your opinion on what's going on here.
crankVR_IO.jpg
crankVR_IO.jpg (207.03 KiB) Viewed 5481 times

CAS_VR_IO.jpg
CAS_VR_IO.jpg (186.56 KiB) Viewed 5481 times

these captures are taken, on input side, from the leads, cas and crank vr+, as the enter the screw block on the MS relay and on the output side from JS10 CAS VROUT and TSel crank VROUT. This is what MS sees....right? The conditioned signals look good ...right, or am I missing something here? If they are good and that is what is being input into the MS what would be causing the tach signal to be erratic and give me lots of synch errors? I don't think the problem is with the VR signals anymore. For all I know your board works fine too but there's something not right somewhere but, again, Im' beginning to think it has nothing to do with Vr signal/conditioning.
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Re: noise filtering

Postby jbelanger » Wed Jun 27, 2012 11:49 am

From those traces, the conditioned signal looks good but the signal from the CAS looks very noisy. To make sure of what the MS sees, you need to check the composite log. That will tell you why you're having sync losses. You may need to change the polarity on the crank signal either by changing the wiring or changing the setting.

Jean
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Re: noise filtering

Postby phongshader » Wed Jun 27, 2012 2:05 pm

here's a data log and synch error log of an attempted start.
Attachments
2012-06-27_09.15.45.zip
(76.33 KiB) Downloaded 171 times
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Re: noise filtering

Postby jbelanger » Wed Jun 27, 2012 4:02 pm

The 2 composite logs don't show any sync loss or error. There are sync losses in the data log but I don't see anything in the composite log. You should post that on the msextra forum.

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Re: noise filtering

Postby phongshader » Wed Jun 27, 2012 5:48 pm

Funny how the log shows synch loss but the error log does not...both were logged at the same time...
I do have a thread on the MSExtra forum that I started before I installed your VR board http://www.msextra.com/forums/viewtopic ... 01&t=45244 and there's plenty of composite and data log files there to see.
What makes you think I may need to change the crank VR polarity? Is there something you see in the crank traces?
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Re: noise filtering

Postby jbelanger » Wed Jun 27, 2012 6:04 pm

phongshader wrote:What makes you think I may need to change the crank VR polarity? Is there something you see in the crank traces?

Since I don't know your complete setup, I'm not sure if this is needed or not. But from your scope traces, you need to be set for the rising edge.

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