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Thread: Green Backup Wire

  1. #1
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    Green Backup Wire

    Since I dont have an instruction manual for my 701- I decided not to take the chance of applying a voltage to the green wire until I researched it online. I assumed it would be a 12V positive signal that would activate the rear camera.

    I find the following strange:

    1. If I touch the wire, it does not completely switch, but does attempt to. On one occasion I did however see a brief "video 2" switch before going back to pc- but that was once. If you hold the wire, it will flicker PC and go blank as if switching, then repeat. I am an electrical engineering student... so I do know a little about electronics. It seems strange to me still, that contact through a single wire (no ground in common with the unit and myself) will make it do this. But it gets stranger.

    2. If I squeeze the green wire- if I squeeze the INSULATED section of wire only (and not the conductor- not the actual wire) it will also do it!

    I really dont know which one of the two I find stranger. Im thinking number 2.
    Does anyone who KNOWS the laws of electricity wanna chime in? Keep it in laymens terms though- I am still a student.

    Before I knew what was triggering the black screen flickers, I had thought there was some kind of loose connection because it would flicker and cut off while I was holding the unit (its in the bigbyte frame) and torquing the frame ever so slightly. Then I would notice that sometimes, no matter how hard I torqued the frame, bounced the unit around, etc., nothing would happen. It took me more than a half hour before I seen the correlation with the green wire. It must have been brushing up against my skin while holding the unit, causing it to flash on and off. But obviously one would worry if their screen flickered on and off for no apparent reason- the green wire is the culprit in this case.

  2. #2
    Fusion Brain Creator 2k1Toaster's Avatar
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    Quote Originally Posted by madintro View Post
    Since I dont have an instruction manual for my 701- I decided not to take the chance of applying a voltage to the green wire until I researched it online. I assumed it would be a 12V positive signal that would activate the rear camera.

    I find the following strange:

    1. If I touch the wire, it does not completely switch, but does attempt to. On one occasion I did however see a brief "video 2" switch before going back to pc- but that was once. If you hold the wire, it will flicker PC and go blank as if switching, then repeat. I am an electrical engineering student... so I do know a little about electronics. It seems strange to me still, that contact through a single wire (no ground in common with the unit and myself) will make it do this. But it gets stranger.

    2. If I squeeze the green wire- if I squeeze the INSULATED section of wire only (and not the conductor- not the actual wire) it will also do it!

    I really dont know which one of the two I find stranger. Im thinking number 2.
    Does anyone who KNOWS the laws of electricity wanna chime in? Keep it in laymens terms though- I am still a student.

    Before I knew what was triggering the black screen flickers, I had thought there was some kind of loose connection because it would flicker and cut off while I was holding the unit (its in the bigbyte frame) and torquing the frame ever so slightly. Then I would notice that sometimes, no matter how hard I torqued the frame, bounced the unit around, etc., nothing would happen. It took me more than a half hour before I seen the correlation with the green wire. It must have been brushing up against my skin while holding the unit, causing it to flash on and off. But obviously one would worry if their screen flickered on and off for no apparent reason- the green wire is the culprit in this case.

    Their logic input is floating. Floating nodes are unpredictable by definition. This is why you always use pull-up or pull-down resistors in your design. You do the same thing yourself. Use a basic micro and write a while(1) { if pin A is high, pin B is high, else pin B is low }. Attach a wire to the pin, and an LED to the output. You will get the same behaviour.
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  3. #3
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    Not exactly laymens terms for me... but its a start, and coming from thecreator of the Fusion Brain, its to be expected...ha. Im going to try to figure out what the heck you are talking about.

    I guess in laymens terms, my thoughts are these:

    How does this single wire (if this is what it is doing) receive a voltage from me? I thought I would need to share a ground, or common, to make a complete circuit.

    and second, why does this insulator allow me to have the same action as touching the bare wire?

    UPDATE: Tesla... of course.

  4. #4
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    Well I have come to learn a little about single wire power transfer, something I thought was impossible without a ground/common, I might add.

    but what about the insulator? How could me touching the insulator overcome its resistence, but not a live wire?

  5. #5
    What can I say? I like serial. Curiosity's Avatar
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    A complete circuit is always required, but the word wire might be what causes confusion. The car's chassis is grounded so anything connected to ground already has half the circuit completed. Any wire connected to battery + that connects to ground completes the circuit and allows the electrons to go back into the battery where they want to go really bad. Electronics is all about slowing and channeling them while they're on that path and everything has some amount of resistance. Metal is just a better conductor.

    A floating or high-Z input is neither on nor off so any change can trigger a transition. It's possible that touching the wire pulls it down for a short period then it returns to floating creating a bounce since the path of least resistance is through you, through the air to the chassis. It all depends on the sensitivity of the trigger circuit.

    But to the point as 2k1Toaster said, get a resistor (4.7K would do). Connect it between the wire and ground to keep it pulled down so it's not effeced by any high impedence noise.

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