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Old 11-28-2011, 12:58 PM   #1
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Looking for solution that I can use to datalogg mutiple sensor in my car.

looking at 4 IAT sensors, 2 o2 sensors, tps, 2 maf sensors, 5 map sensors, etc

something cheap atleast logs as fast as megasquirt does with its normal logging speed.
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Old 11-28-2011, 01:13 PM   #2
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How many sensors total, and does it need to be standalone, or can it log to a PC?

The easy answer is (depending on how many inputs) would be:
Demux->ADC uC Pin (AVR/PIC/etc) x2 (one for reading line voltages (MAP/MAF), one for reading resistance type sensors (IAT/CLT)) which would then write the values serially to a PC to be interpreted (python is great for this). Making a board to hold all of it would be the hardest part. This would be the cheapest solution. You can build a picaxe (programmed in BASIC) burner for like <5 bucks with parts from RadioShack. The chips themselves come in between 3 and 7 bucks depending on the features you need. You can also go the AVR route (my preference) but some people are a bit intimidated by C/makefiles/thatsortofthing.

If you want a 'Controller Box' that writes to an SD card for after the fact retrieval, it is a bit trickier, but not terrible.

Easy Button:
http://www.sparkfun.com/products/10216
Serial->SD card backpack. All the ease of serial communication(and PC retrieval), all the cost of someone doing it for you.

Hard mode:
Build an SD card slot onto the board, write to it with SPI.

Last edited by Jeff_Ciesielski; 11-28-2011 at 01:39 PM. Reason: Edited for clarity
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Old 11-28-2011, 01:27 PM   #3
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I wrote up some microcontroller code to log:

3 IR temp sensors, 4 wheel speed, 2 position (steering angle/Throttle), voltage, and a 3-axis accel.

put it out in CSV format on an SD card (through Software bit-bang SPI).
Probably the most time consuming thing will be the physical solution. box, wiring, sensor placement, etc.

The code is pretty simple and its easier if you use a board with a lot of user support to identify any pitfalls in the source code provided with the MCU.


Or, dish out big money for a data logging solution?
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Old 11-28-2011, 02:23 PM   #4
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I'lll have to figure out how many more sensors I plan to log. What about the audino boards, canthose be used?
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Old 11-28-2011, 02:35 PM   #5
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Quote:
Originally Posted by Techsalvager View Post
I'lll have to figure out how many more sensors I plan to log. What about the audino boards, canthose be used?
yes, we used one. but tbh, the arduino is not a good deal in the hardware aspect of things. the clock speed is lacking, the ADC is about the slowest design you can get, and it only has one SPI and I2C bus. All for about the price of a 72-100mhz cortex with 2-3x as many peripherals. The nice thing about the arduinos is exactly what I was saying above, the user support is so ******* huge they have all the code for everything you could ever need to do written up.

We didn't do any speed benchmarking, but we got a total of 12 sensors running at 25hz, which is excessively fast for most data logging applications.

You can get nice addons too, for GPS, ethernet, and I think possibly CANBUS. I know they make the "datalogger" shield with the generic PCB and a SD card slot on, but its a waste when you can use the GPS one instead. The reason is you can just buy the SD card controller that they use, and then hook it up directly to the software SPI pins they use and the source code will work.

Tech, if you decide to go with this, let me know, I can provide you with our code for "educational" use.

If you are not familiar with coding in C, the arduino is an excellent starting point and plenty beefy for low number of sensors at fast speeds, or high number of sensors at slower speeds. Without any prior testing, I think you could easily run a good 15 sensors at +25hz if you wanted (depending on what communication protocols you use and how frequently you wrote to SD). Do note, these are generally random number guesstimations based on my past experience with the Arduino Mega on the ATmel 1280.
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Old 11-29-2011, 03:13 AM   #6
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Old 11-29-2011, 06:50 AM   #7
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I was/am a beta tester for the Everlog unit, it's brilliant.
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Old 11-29-2011, 10:10 AM   #8
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How is everlogs situation now with lap based analytics? Basically the functionality to organize data into laps and sectors instead of a long array of positions and measurements?

If they support typical video export formats (for e.g. racechrono2avi) I do have a Matlab interface that does lap-analytics and complex visualisation.
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Old 11-29-2011, 07:30 PM   #9
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whats the logging rate of everlog
Also it looks limited on data inputs.

nvm 50hz max. depedent on ecu.
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Old 12-20-2011, 06:09 PM   #10
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Quote:
Originally Posted by damir130 View Post
How is everlogs situation now with lap based analytics? Basically the functionality to organize data into laps and sectors instead of a long array of positions and measurements?

If they support typical video export formats (for e.g. racechrono2avi) I do have a Matlab interface that does lap-analytics and complex visualisation.
Hi, I hope it's ok to reply to your questions here - I'm one of the developers of Everlog.

Everlog was initially conceived as an always-on USB datalogger to solve the problem of needing a laptop in your car all the time, especially on track. We wanted a unit that would always be logging and could be used to help diagnose problems after they've occurred.

Once we had this functionality we started to improve our utility for track day usage, initially through video overlay. We currently export to MLV, and aim to support additional formats based on customer demand.

Driver development tools are our current focus, with our first step being the addition of lap/split/delta time in video overlay (example here : http://youtu.be/r3sZGVZHwYk). We allow the positioning of lap start and any number of split points. These can then be applied to other data logs on the same track. We will be able to split logs into individual laps in the very near future.

If you want super high accuracy lap analysis for viewing alternate lines through corners, we're probably not the product for you - Race Logic or similar are a better place to start. Our aim is to provide 75% of the functionality to track day drivers for 33% of the cost.

We developed this product because it was something that we wanted, and couldn't find an alternative without paying for many features we wouldn't use. We hope it will be of use to people with similar requirements.

Cheers, Brett
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Old 12-20-2011, 07:58 PM   #11
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Hiya Bret, could you take a look at racechrono2avi? Especially its export format.. Its really not much more then a .csv data dump with some header lines and timestamped columns for all the logged data. They all seem to be referenced at the same time by the internal clock (dunno if you are running varying sampling rates).

If you could produce that output format, then:
You have a nice and ready open source movie generation suite that you don't have to devellop or maintain
Users can take the offline racechrono version and import files to do simple analytics. There is some usefull stuff in there.

I could probably reconstruct something similar from the .mlv file in no time.

And I disagree that someone should start at racelogic..wel maybe some people. Based on what I have lying around here at the moment, I could do 95% of the racelogic stuff with everlog. If you ever need any help or example scripts, just let me know.
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