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Thread: Analogue inputs acting funny..

  1. #1
    Variable Bitrate rEegLer's Avatar
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    Analogue inputs acting funny..

    Hey guys,

    I was just about to put my CarPC in my car but I thought I'd test my FB with my simulated steering wheel control circuit and I hooked everything up and noticed that my other ports were measuring a voltage but nothing was there. I took it out and setup a test config file that showed all the ports and their voltages. This is what I got:


    In this pic, I have 5v connected to port 1 (Port 1 on FB, Port 0 in configurator) and the other ports are reading these voltages. You will notice that the voltages decrease as the port increases, kinda interesting.

    Anyone know why this is? Do I have a fried board? I don't remember doing anything to fry it but who knows. In an attempt to get it to work, I pressed the reset button and switched off power and turned it back on and it said that it was version 3 not 4 when I reinstalled the drivers (I was desperate ).

    Any help would be greatly appreciated!
    Love

  2. #2
    Raw Wave Rob Withey's Avatar
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    Old Systems retired due to new car
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  3. #3
    Variable Bitrate rEegLer's Avatar
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    Thanks, wasn't sure what to search for!
    Love

  4. #4
    Fusion Brain Creator 2k1Toaster's Avatar
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    Yup, it is normal. Just left over charge on the sampling capactior. Once you hookup another sensor, it will read correctly since it wont float anymore.
    Fusion Brain Version 6 Released!
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    Quote Originally Posted by 2k1Toaster View Post
    Yup, it is normal. Just left over charge on the sampling capactior. Once you hookup another sensor, it will read correctly since it wont float anymore.
    im not sure i ever saw an answer to this question, but is adding a jumper to blank inputs a safe way to zero them out? Will it do damage to the FB?
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  6. #6
    Fusion Brain Creator 2k1Toaster's Avatar
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    Quote Originally Posted by Sonicxtacy02 View Post
    im not sure i ever saw an answer to this question, but is adding a jumper to blank inputs a safe way to zero them out? Will it do damage to the FB?
    Why zero them out? If they aren't in use, then you aren't doing anything with them and they have the parasitics. As soon as you attach something to prevent them from floating such as a sensor or aything where you will use the input it will measure accurately. It is only apparent when measuring nothing.

    If you really want to make it go away, then (assuming you are using consecutive analogue inputs for your array of sensors) jumper between the AIN pin and GND. Be careful not to short power and ground as this will signal destruction of your Fusion Brain.
    Fusion Brain Version 6 Released!
    1.9in x 2.9in -- 47mm x 73mm
    30 Digital Outputs -- Directly drive a relay
    15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
    Buy now in the MP3Car.com Store

  7. #7
    Variable Bitrate rEegLer's Avatar
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    Yea it was just a little weird, that's all. Just making sure my FB wasn't damaged.

    One quick question. When I hook up ~12V to the FB (and change the jumpers previous to the powerup), nothing really works. No AN inputs work and my MDX program errors out with .Net. When I hookup 12v while it is USB powered, everything works fine, AN inputs and digital outputs. Is this bad? I couldn't find anything written against this in the manual.
    Love

  8. #8
    Fusion Brain Creator
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    Quote Originally Posted by rEegLer View Post
    Yea it was just a little weird, that's all. Just making sure my FB wasn't damaged.

    One quick question. When I hook up ~12V to the FB (and change the jumpers previous to the powerup), nothing really works. No AN inputs work and my MDX program errors out with .Net. When I hookup 12v while it is USB powered, everything works fine, AN inputs and digital outputs. Is this bad? I couldn't find anything written against this in the manual.
    It shouldn't happen. It isnt bad to use both power sources, but it's not really good practice and can induce ground loops, among other things. Can you take a picture of the jumpers in each config?

  9. #9
    Constant Bitrate ACCLR8N's Avatar
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    Quote Originally Posted by Sonicxtacy02 View Post
    im not sure i ever saw an answer to this question, but is adding a jumper to blank inputs a safe way to zero them out? Will it do damage to the FB?
    I'm running a jumper in front of each of my sensor inputs (every other port). The residual charge was throwing off all my sensors to some degree Tach, Speedo, oil pressure, fuel level. Even my digital signals such as check engine and alternator I have on on SPDT relays shunted to ground when off. http://www.mp3car.com/vbulletin/fusi...capacitor.html

  10. #10
    Variable Bitrate rEegLer's Avatar
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    How accurately can the fb measure voltage? I have my steering wheel controls hooked up hookep up through a voltage divider and when I push one button, I'll get a voltage of 2.49577 for example but it flickers between that and 2.49166 somewhat randomly. I haven't tried the every-other port idea but I'm also not sure if it's the quality of my components or electrical noise.
    Love

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