DIY Autotune Hall Sensor using Opto Isolator MS3/x

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DIY Autotune Hall Sensor using Opto Isolator MS3/x

Postby kenjfox » Wed Sep 06, 2017 6:48 pm

Hi All,

I'm having no luck getting a signal through my crank circuit with VR, so am trying opto in. Looking for help on the board wiring. I have a JimStim and can see a signal at the Tach Select point. Am a bit confused about power supply requirements. I plan to use the DIY Autotune Hall effect sensor (new red aluminum one) with 12v feed. Installed pullup inside the sensor's wiring.

Would one of these options work for me?
viewtopic.php?f=101&t=52333megasquirt%20hall%20effect%20wiring
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Re: DIY Autotune Hall Sensor using Opto Isolator MS3/x

Postby billr » Wed Sep 06, 2017 9:32 pm

The opto input is not used for a Hall CKP sensor. Let's start by having you post your MSQ. Are you saying you get no rpm using the JimStim? Post a picture of the stim, showing the jumper and switch settings. While you have the camera out, it wouldn't hurt to take pictures of the mainboard, too...
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Re: DIY Autotune Hall Sensor using Opto Isolator MS3/x

Postby kenjfox » Wed Sep 06, 2017 11:10 pm

Thanks for you response Bill. I used the opto because I think I have a problem in my VR circuit. I followed the path for opto, going low, and got a stim reading and the car now starts. Thanks.
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Re: DIY Autotune Hall Sensor using Opto Isolator MS3/x

Postby racingmini_mtl » Wed Sep 06, 2017 11:46 pm

You could have a problem using the opto circuit because it is frequency limited. What wheel type are you using with that Hall sensor?

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Re: DIY Autotune Hall Sensor using Opto Isolator MS3/x

Postby kenjfox » Fri Sep 08, 2017 2:33 pm

Hmmm. I'm using a 36-2 wheel. The chip itself seems plenty quick (3 micro seconds rise/fall) I just got the "Dual VR 2.1" card that I can use if needed (ha- just noticed I bought it from you-eh?). When the engine is running, the lost sync count is in the single digits- which I suppose is good, right? I grabbed a trigger and composite log from today's trial. One thing I've been thinking about is that the sensor is connected to unregulated 12v just like any other accessory. See any issue with that?

If you wouldn't mind taking a peek at the logs I'd appreciate it.
Attachments
2017-09-08_Third Run.csv
Composite
(1.02 MiB) Downloaded 2 times
2017-09-08 tooth.csv
Tooth
(37.95 KiB) Downloaded 9 times
Exocet Tune 2017-09-08.msq
Tune
(284.69 KiB) Downloaded 8 times
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Re: DIY Autotune Hall Sensor using Opto Isolator MS3/x

Postby jsmcortina » Sat Sep 09, 2017 3:40 am

Even though the optoisolator itself may be reasonably quick, the input circuit has capacitors on there which greatly slow down the signal. They are there for fuel-only installs triggering from the coil negative.

Is this a stock crank wheel and sensor phasing? From the tooth log, the phasing doesn't look great with the missing tooth right where the engine is changing speed a lot.

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Re: DIY Autotune Hall Sensor using Opto Isolator MS3/x

Postby kenjfox » Sat Sep 09, 2017 10:59 am

Thanks James. Forgive me but I'm not exactly sure what you mean by "stock crank wheel and sensor phasing". The wheel is an aftermarket 36-2 for Miata from 949 racing. The sensor is a DIY autotune Hall effect on a homemade bracket. I tried to match the OEM position as closely as I could- but have not set the exact timing. On the ignition settings, I picked "Miata 36-2" and Ignition Input Capture is "Rising Edge".

I know that there is another 36-2 wheel for Miata from a different vendor, and I think that wheel is the one that spawned the "Miata 36-2" settings. I'm ignorant to the possibility of two 36-2 wheels for the same engine being different. I'll research if the possibility exists.

I'll wire up the new VR sensor. In the meantime, can you point me to an article on phasing? I was just looking at the composite log for any blips on the bottom red line. Obviously need need to educate myself a bit more.

One other thing, the engine does start right up, revs up and then stalls within about 5 seconds. I can keep it running with more throttle. I was hoping to get it to idle so I can dial in the timing and eliminate a variable. Currently though it is running super rich (7-8) and it sounds like it is missing (like it has really big cams). I dropped the Required Fuel by about 20% (just for testing), but AFR remained the same.
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