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Old 02-27-2013, 02:55 PM   #1
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Default Second optoisolator on MS2

Even after upgrading to MS2 I am still getting a loss of sync or random dropouts, not as often as with MS1 but still enough to annoy me. While looking around I have found what seems to be the end all solution to the problem, which is making a second optoisolator circuit. I have found a diagram posted by Brain floating which I posted along with a picture of it on a board. Please verify that it in fact looks correct.
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Second optoisolator on MS2-2ndcas_input.gif   Second optoisolator on MS2-dscf6117g.jpg  
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Old 02-27-2013, 03:19 PM   #2
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is the above yours?


do you have a composite log of your current sync loss?
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Old 02-27-2013, 03:25 PM   #3
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The above is not mine, just one I found and scribbled out what I believe does not pertain to the circuit and changed pin 2 from spr1 to IAC1A. I don't have a current log with it happening as my old tuning laptop's motherboard fried. I can probably get one next time I have the car out but the way the weather has been lately that may be a week or two.
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Old 02-27-2013, 03:28 PM   #4
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I did purchase 15ft of shielded wire which I am going to use to rewire both CAS signals directly to the Megasquirt box to see if it makes a difference.
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Old 02-27-2013, 03:30 PM   #5
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I'd like to see a composite log of your inputs from the CAS.

Circuit above seems correct, Been a while, just follow the diagram, did you need it again?
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Old 02-27-2013, 03:59 PM   #6
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Quote:
Originally Posted by duffbuster243 View Post
While looking around I have found what seems to be the end all solution to the problem, which is making a second optoisolator circuit.
A second opto is a second band-aid.

If you want a proven reliable input circuit, build this:

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Old 02-27-2013, 04:09 PM   #7
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even better and still incredibly easy.
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Old 02-27-2013, 04:46 PM   #8
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Quote:
Originally Posted by Joe Perez View Post
A second opto is a second band-aid.

If you want a proven reliable input circuit, build this:

I'm not quite good with circuits, and that appears simple, almost looks like it would be easier to do on a separate wafer. Does anyone have a picture of this done?
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Old 02-27-2013, 04:59 PM   #9
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Quote:
Originally Posted by duffbuster243 View Post
I'm not quite good with circuits, and that appears simple, almost looks like it would be easier to do on a separate wafer. Does anyone have a picture of this done?
You could easily build it in the proto area, assuming it's not already filled with a bunch of other stuff. But yeah, a separate board would be ideal. If I weren't so lazy, I'd design a little JB-style daughterboard and offer them for sale.

I don't have any pictures of the actual circuit built, apart from this one, which is worthless for your purposes:


(It's the circuit that the red/wht and blk/wht wires go into.)


In all seriousness, would you guys actually buy a little board containing this dual-input conditioning circuit?

Last edited by Joe Perez; 02-27-2013 at 05:07 PM. Reason: typetoofastandmissshpel
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Old 02-27-2013, 05:05 PM   #10
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Quote:
Originally Posted by duffbuster243 View Post
I did purchase 15ft of shielded wire which I am going to use to rewire both CAS signals directly to the Megasquirt box to see if it makes a difference.
It won't. (sorry)
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Old 02-27-2013, 05:08 PM   #11
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Quote:
Originally Posted by Joe Perez View Post
A second opto is a second band-aid.
And your evidence for this?
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Old 02-27-2013, 05:09 PM   #12
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And your evidence for this?
Dictum meum pactum.
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Old 02-27-2013, 05:11 PM   #13
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Sorry, you need to try harder.
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Old 02-27-2013, 05:12 PM   #14
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I tried really hard several years ago when I was doing the initial install on my '92. Wound up saying "**** it" and building a 36-1 crankwheel setup. (This was, admittedly, a rather disproportionate response to the situation.)

The 40106 solution has excellent filtering and hysteresis, and doesn't rely upon current-mode devices which offend my sensibilities.
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Old 02-27-2013, 05:40 PM   #15
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I'm willing to try this. I added my inputs/outputs on. Is this correct?
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Old 02-27-2013, 05:50 PM   #16
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Quote:
Originally Posted by duffbuster243 View Post
Even after upgrading to MS2 I am still getting a loss of sync or random dropouts, not as often as with MS1 but still enough to annoy me. While looking around I have found what seems to be the end all solution to the problem, which is making a second optoisolator circuit. I have found a diagram posted by Brain floating which I posted along with a picture of it on a board. Please verify that it in fact looks correct.
Do you have a composite log showing loss of sync?
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Old 02-27-2013, 06:07 PM   #17
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That's correct. Depending on how you have your cam input wired now, you may need to flip the polarity setting (in software) for that input after you build this circuit. I can't remember what it's called on the MS2. Also, you'll need to re-calibrate the hardware latency. This circuit has a very long time-constant by design.

The value and stability of C120 and C125 are highly critical. Use low-tolerance parts here (eg: 5%, C0G).
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Old 02-27-2013, 06:13 PM   #18
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Quote:
Originally Posted by Ben View Post
Do you have a composite log showing loss of sync?
I do not, How do I do a composite log in Tunerstudio?
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Old 02-27-2013, 07:40 PM   #19
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Under the diagnostics tab.
You're chasing your tail if you haven't taken a composite log first. It will show you (if) you have a sync problem, and if so, which sensor is not coming through.

I am generally amazed at when I see a report of a sync problem on a Miata. I personally have numerous Miata installs under my belt, as in I can't count/remember them all, and have never had a sync problem. As a company, Miata is one of our top selling applications, and I don't recall any sync problems with any of our prebuilt units if correctly installed.
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Old 02-27-2013, 09:21 PM   #20
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What makes the CD40106 trigger superior to an opto-isolator?
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