# Tutorial - Air Ride Suspension

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• 02-19-2009, 12:48 AM
wrxyboy
Quote:

Originally Posted by 2k1Toaster
That logic function takes an analogue input "Front Left" and puts the actual value in a variable "Front Left Variable". That is it.

If you want to do something useful, like make Front Left Variable PSI not voltage, then you need to send the analogue input through the psi function then to to variable.

So the air sensor function that you posted above will convert the voltage to psi? Since there is no quick block for that in the configurator i would need to write that in with an xml editor correct. Thanks
• 02-19-2009, 09:57 PM
wrxyboy
when i open up my fusion center the program runs perfect but when i open up the configuator and try to open the xml file i get this error what does this error mean. Thanks

http://i27.photobucket.com/albums/c1...95-54-04PM.png
• 02-21-2009, 04:18 PM
wrxyboy
Quote:

Originally Posted by 2k1Toaster
That logic function takes an analogue input "Front Left" and puts the actual value in a variable "Front Left Variable". That is it.

If you want to do something useful, like make Front Left Variable PSI not voltage, then you need to send the analogue input through the psi function then to th variable.

So does the function at the top convert it to psi and why does it go into the negatives when i add 5v on the virtual brain. Shouldnt the 5v indicate somewhere around 150psi if i am using the 150psi sending unit. Thanks for all the help you have done so far.
• 02-24-2009, 12:49 AM
2k1Toaster
Quote:

Originally Posted by wrxyboy
So does the function at the top convert it to psi and why does it go into the negatives when i add 5v on the virtual brain. Shouldnt the 5v indicate somewhere around 150psi if i am using the 150psi sending unit. Thanks for all the help you have done so far.

It goes negative because I made a typo. The 18.xx and the rest of the function is switched on the last subtract node. Just change those around so it looks like this:

http://img9.imageshack.us/img9/1249/...alfunction.jpg

Also, 5v gives you 600+ psi.

using a 100ohm resistor for R1 of a voltage divider, you get:

FB Voltage = 5 * (sensor/(sensor + 100))

The pressure function models this: y = 8.4879x^3 - 27.568x^2 + 49.943x - 18.313 where y is in pressure and x is in volts.

150psi ~= 3.29v
• 02-24-2009, 12:52 AM
2k1Toaster
Software post uptop is updated
• 02-24-2009, 01:41 AM
wrxyboy
thank you now explaining that and now everything is beginning to make sense. I couldnt make out how the equation would work and cause the values to be negative. Now you you said that 5v will equal 600psi, how is that possible with the sending unit only being able to have a max of 400psi or is it that the unit will never reach 5v thus 600psi will never be obtained. Thank you once again for all your help and great product.
• 02-24-2009, 01:45 AM
2k1Toaster
the sensor will never give out a resistance that could possibly equal 5v input, so you would never get 600psi read in. If you for some strange reason did get 5v in, the actual pressure would be off since the equation blows up outside of its bounds, which in reality are closer to 3.3v instead of 5v since that is the max it can handle.

If you want to be more accurate then all you do is measure more data points and create a larger polynomial series.
• 02-24-2009, 02:31 AM
wrxyboy
So would this air module function work with the 400psi sending unit or only the 150psi sending unit. I think i may need to purchase the dakota digital reading unit to make the equation more accurate.
• 02-24-2009, 04:46 PM
2k1Toaster
Quote:

Originally Posted by wrxyboy
So would this air module function work with the 400psi sending unit or only the 150psi sending unit. I think i may need to purchase the dakota digital reading unit to make the equation more accurate.

No it only works with the 150psi one.

If you want to use the 400 one then you would need to write a seperate function that would calibrate that
• 02-24-2009, 05:43 PM
GizmoQ
Quote:

Originally Posted by 2k1Toaster
No it only works with the 150psi one.

If you want to use the 400 one then you would need to write a seperate function that would calibrate that

Can you check my math on the 400psi polynomial from the other air pressure thread?
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