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Thread: 150 PSI Air Pressure Sensor

  1. #41
    Variable Bitrate
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    Well what if I connect it and see what happens? If it can't work then I can probably wire up relays to switch off each other. This is probably how I will wire up the setup.




  2. #42
    Fusion Brain Creator
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    well, connecting it and seeing what happens could cause one of teh two devices to blow up, at worst.

    I'll explain in depth later today.

  3. #43
    The Last Good Gremlin GizmoQ's Avatar
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    Hey, Greenman100. I plotted your graph from post 9 and I'm concerned about the accuracy of this data. If this is right then the drop off of R min after point 9 leads me to question any reading above 116PSI. The percent variance goes down for the first five points (good), but then goes up one point, down the next and then proceeds up almost exponentially (bad). If I were to extrapolate this trend out to 250PSI, R min would be less than half R max and below the previous four R min values.

    If I were to trust this data, I figure based on the slope of the R typical and PSI is approximately 17.176X and 14.5X, respectively. Therefore, my FB data labelshould be based on the formula: (input data/17.176)*14.5

    Did I calculate that right?

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  4. #44
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    I am trying to get this sort of thing working. With all the discussion in this thread, what is the correct wiring diagram for sensors to fb?

  5. #45
    The Last Good Gremlin GizmoQ's Avatar
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    See post 37
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  6. #46
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    Ok so is the power source 12v or 5v? I thought the purpose of the resistor was to change the 12v power source to 5v so the FB could use it.

    All I am wanting to do is display the pressure from my bags on the LCD screen. I don't want to control the valves themselves through the computer. Anyone know of an easy way to display this on screen?

  7. #47
    Fusion Brain Creator
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    The power source is 5v. You need the resistor. Its purpose is not changing the voltage from 12 to 5v.

    Do your sensors already have anything attached to them?

  8. #48
    Fusion Brain Creator 2k1Toaster's Avatar
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    Quote Originally Posted by greenman100 View Post
    The power source is 5v. You need the resistor. Its purpose is not changing the voltage from 12 to 5v.


    If you look here at figure 1: http://en.wikipedia.org/wiki/Voltage_divider

    you see that it requires 2 sources of impedance. When you hook up just your sensor to a constant voltage source (your car), you get a varying current output with pressure change. The FB doesnt read current, it reads voltage. So sending the varying current through another resistor then gives you a varying voltage output which the FB uses. That is the simple explanation of what the second resistor does.
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  9. #49
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    Quote Originally Posted by greenman100 View Post
    The power source is 5v. You need the resistor. Its purpose is not changing the voltage from 12 to 5v.

    Do your sensors already have anything attached to them?
    I have not purchased the sensors yet. I am in the stage of building in carputer right now. I am just researching this to see if I can do it. I currently have air ride on my blazer and don't have room for my gauges due to the screen I am installing. I have a switchbox to actually control the airflow in and out of the bags but want to display the pressure on the screen and do away with the existing gauges.

    It appears this is easily doable but I would have to write a skin to use in my front end to display the pressures, correct?

  10. #50
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    Yup, but the skin shouldn't take more than an hour tops.

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