[PIC] data acquistion and logging strategies

[Bob Blick]

I was thinking about someday making a simple device for quick review of a few automobile parameters. I'm not doing any real racing anymore but I do still autocross and the occasional hillclimb, so the races are either under a minute or under three minutes. Actually a lap on most road courses is usually under four minutes. Basically I am not the kind of person who pores over data or race videos or keeps a log book of tire temperatures. I don't even really care about improving my driving that much, but I do care about the car, so after a run I'd like to look at data from the last lap and see how things went. Stuff like air/fuel mixture, manifold pressure, engine RPM, maybe throttle position. I'd have some display I can scroll through. This is not from OBD2 or a diagnostic port, I'd be grabbing data mostly directly.

My car is not running right now, so it's not something I'm likely to do anything about until next year, if ever. Previous datalogging gadgets I have used or built just haven't been any fun so it'd be nice to do something simple that's more of a scrolling display of the last minute.

Obviously one can sample data real fast and store all of it. That uses lots of memory. Sampling or averaging say once per second doesn't use much data, but can miss quick little events. So I was thinking about storing just the peak minimum and peak maximum once a second. Sample fast, store and reset peaks once a second. It only uses twice as much memory as sampling once a second, but it'll catch any weird glitches.

Thoughts?

Thanks,
Bob
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[John Gardner]

I've been away from this for a long time, Bob - What's the BW on AFR

sensors & manifold pressure sensors these days? Can you see the in-

dividual cylinders in the data? Do you want to?

RPM & Throttle position change relatively slowly by comparison.

IIRC your war horse is an RX-7 with a Ford V8 transplant?

Sounds like fun anyway...

Jack

...


On 9/9/17, Bob Blick <***@outlook.com> wrote:
> I was thinking about someday making a simple device for quick review of a
> few automobile parameters. I'm not doing any real racing anymore but I do
> still autocross and the occasional hillclimb, so the races are either under
> a minute or under three minutes. Actually a lap on most road courses is
> usually under four minutes. Basically I am not the kind of person who pores
> over data or race videos or keeps a log book of tire temperatures. I don't
> even really care about improving my driving that much, but I do care about
> the car, so after a run I'd like to look at data from the last lap and see
> how things went. Stuff like air/fuel mixture, manifold pressure, engine RPM,
> maybe throttle position. I'd have some display I can scroll through. This is
> not from OBD2 or a diagnostic port, I'd be grabbing data mostly directly.
>
> My car is not running right now, so it's not something I'm likely to do
> anything about until next year, if ever. Previous datalogging gadgets I have
> used or built just haven't been any fun so it'd be nice to do something
> simple that's more of a scrolling display of the last minute.
>
> Obviously one can sample data real fast and store all of it. That uses lots
> of memory. Sampling or averaging say once per second doesn't use much data,
> but can miss quick little events. So I was thinking about storing just the
> peak minimum and peak maximum once a second. Sample fast, store and reset
> peaks once a second. It only uses twice as much memory as sampling once a
> second, but it'll catch any weird glitches.
>
> Thoughts?
>
> Thanks,
> Bob
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> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>
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[Bob Blick]

Hi Jack,

At idle, yes, sensors are fast enough to see individual cylinders. But I'm pulling the mixture data from an AEM meter which is probably filtered, and there are other things smoothing the exhaust before the sensor too.

No more RX-7. I have actually gotten rid of all vehicles that need to be towed. And my tow vehicle too, no more F-250. That was an interesting decision, I'm sure some can relate to the scary thought of life without a pickup truck :) But I have a utility trailer and a hitch on the family car, so I'm not quite helpless. But only streetable vehicles now, and no more "real" racing.

Friendly regards,
Bob

________________________________________
From: piclist-***@mit.edu <piclist-***@mit.edu> on behalf of John Gardner

I've been away from this for a long time, Bob - What's the BW on AFR

sensors & manifold pressure sensors these days? Can you see the in-

dividual cylinders in the data? Do you want to?

RPM & Throttle position change relatively slowly by comparison.

IIRC your war horse is an RX-7 with a Ford V8 transplant?

Sounds like fun anyway...

Jack

...


On 9/9/17, Bob Blick <***@outlook.com> wrote:
> I was thinking about someday making a simple device for quick review of a
> few automobile parameters. I'm not doing any real racing anymore but I do
> still autocross and the occasional hillclimb, so the races are either under
> a minute or under three minutes. Actually a lap on most road courses is
> usually under four minutes. Basically I am not the kind of person who pores
> over data or race videos or keeps a log book of tire temperatures. I don't
> even really care about improving my driving that much, but I do care about
> the car, so after a run I'd like to look at data from the last lap and see
> how things went. Stuff like air/fuel mixture, manifold pressure, engine RPM,
> maybe throttle position. I'd have some display I can scroll through. This is
> not from OBD2 or a diagnostic port, I'd be grabbing data mostly directly.
>
> My car is not running right now, so it's not something I'm likely to do
> anything about until next year, if ever. Previous datalogging gadgets I have
> used or built just haven't been any fun so it'd be nice to do something
> simple that's more of a scrolling display of the last minute.
>
> Obviously one can sample data real fast and store all of it. That uses lots
> of memory. Sampling or averaging say once per second doesn't use much data,
> but can miss quick little events. So I was thinking about storing just the
> peak minimum and peak maximum once a second. Sample fast, store and reset
> peaks once a second. It only uses twice as much memory as sampling once a
> second, but it'll catch any weird glitches.
>
> Thoughts?
>
> Thanks,
> Bob
>
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[John Ferrell]

Just a couple of personal observations:

All logging is more useful when you have a long history to compare it with.

Logging to a thumb drive or a flash drive is not all that difficult or
expensive.


On 9/9/2017 2:50 PM, Bob Blick wrote:
> I was thinking about someday making a simple device for quick review of a few automobile parameters. I'm not doing any real racing anymore but I do still autocross and the occasional hillclimb, so the races are either under a minute or under three minutes. Actually a lap on most road courses is usually under four minutes. Basically I am not the kind of person who pores over data or race videos or keeps a log book of tire temperatures. I don't even really care about improving my driving that much, but I do care about the car, so after a run I'd like to look at data from the last lap and see how things went. Stuff like air/fuel mixture, manifold pressure, engine RPM, maybe throttle position. I'd have some display I can scroll through. This is not from OBD2 or a diagnostic port, I'd be grabbing data mostly directly.
>
> My car is not running right now, so it's not something I'm likely to do anything about until next year, if ever. Previous datalogging gadgets I have used or built just haven't been any fun so it'd be nice to do something simple that's more of a scrolling display of the last minute.
>
> Obviously one can sample data real fast and store all of it. That uses lots of memory. Sampling or averaging say once per second doesn't use much data, but can miss quick little events. So I was thinking about storing just the peak minimum and peak maximum once a second. Sample fast, store and reset peaks once a second. It only uses twice as much memory as sampling once a second, but it'll catch any weird glitches.
>
> Thoughts?
>
> Thanks,
> Bob

--
John Ferrell W8CCW
Julian NC 27283
It is better to walk alone,
than with a crowd going the wrong direction.
--Diane Grant


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[Bob Blick]

Hi John,

I definitely have done that, and also had lot of different types of data available, like brake fluid pressure, steering wheel angle etc. It just ended up not being interesting to me. This time mostly I just want to be able to glance at a big bright "chart recorder" display of the last 60 seconds of a sensor, and be able to twist a switch to change to a different sensor.

Cheerful regards,

Bob

________________________________________
From: piclist-***@mit.edu <piclist-***@mit.edu> on behalf of John Ferrell

Just a couple of personal observations:

All logging is more useful when you have a long history to compare it with.

Logging to a thumb drive or a flash drive is not all that difficult or
expensive.


On 9/9/2017 2:50 PM, Bob Blick wrote:
> I was thinking about someday making a simple device for quick review of a few automobile parameters. I'm not doing any real racing anymore but I do still autocross and the occasional hillclimb, so the races are either under a minute or under three minutes. Actually a lap on most road courses is usually under four minutes. Basically I am not the kind of person who pores over data or race videos or keeps a log book of tire temperatures. I don't even really care about improving my driving that much, but I do care about the car, so after a run I'd like to look at data from the last lap and see how things went. Stuff like air/fuel mixture, manifold pressure, engine RPM, maybe throttle position. I'd have some display I can scroll through. This is not from OBD2 or a diagnostic port, I'd be grabbing data mostly directly.
>
> My car is not running right now, so it's not something I'm likely to do anything about until next year, if ever. Previous datalogging gadgets I have used or built just haven't been any fun so it'd be nice to do something simple that's more of a scrolling display of the last minute.
>
> Obviously one can sample data real fast and store all of it. That uses lots of memory. Sampling or averaging say once per second doesn't use much data, but can miss quick little events. So I was thinking about storing just the peak minimum and peak maximum once a second. Sample fast, store and reset peaks once a second. It only uses twice as much memory as sampling once a second, but it'll catch any weird glitches.
>
> Thoughts?
>
> Thanks,
> Bob


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[Nicola Perotto]

Hi Bob,

On 09/09/2017 20:50, Bob Blick wrote:
> I was thinking about someday making a simple device for quick review of a few automobile parameters. ...
because the constraints for power and cost are relaxed, I would use one or more
PIC for the acquisition and a Raspberry or similar as frontend and logger. You
can have the display you want and program it with whatever language!
      Nicola

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h

[Bob Blick]

Yes, exactly!

I'll need a device to activate a relay or bend a signal here or there based on sensor data, so I'll have that aggregate a couple of other signals and send them to a frontend/logger.

I could even use this STM32F746 Discovery I have here, if I wanted to make it really flashy looking.

But mostly I was thinking about the peak min / peak max method of acquisition. It's the mode I most often use my oscilloscope.

Cheerful regards,

Bob


________________________________________
From: piclist-***@mit.edu <piclist-***@mit.edu> on behalf of Nicola Perotto

Hi Bob,

On 09/09/2017 20:50, Bob Blick wrote:
> I was thinking about someday making a simple device for quick review of a few automobile parameters. ...
because the constraints for power and cost are relaxed, I would use one or more
PIC for the acquisition and a Raspberry or similar as frontend and logger. You
can have the display you want and program it with whatever language!
Nicola

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