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Autofocus/image stabilizaion extension

  1. Aug 13, 2007 #1
    Hello,

    I want to extend the wires of my camcorder's focus motor and image stabilization, its about two 2 inches long and I need make them both about 30inches. Would it still work properly especially the image stabilization which calculates and compensates shakes and vibrations quickly, if it won't work what do I need to fix the problem.
    This project is very important to me any help would be very appreciated.
    thank you.
     
  2. jcsd
  3. Aug 13, 2007 #2

    berkeman

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    The motor wires shouldn't be too sensitive to wire length. Maybe use one bump up in wire size (lower AWG number here in the US), and try to make the patched-in wire section look the same physically (same spacings and bundlings or whatever). How is image stabilization done? I thought it was generally done to the image, but it sounds like you are saying your camcorder has some solenoid arrangement?

    Oh, and you realize that doing this will void the camcorder's warrantee, right?
     
  4. Aug 13, 2007 #3
    the stabilizer uses gyro sensors to sense shake the camcorder then compensates for shake or vibration by shifting an optical element inside the lens assembly with a linear motor.

    How much would silver or gold wire help over copper?
     
  5. Aug 13, 2007 #4
    I will try but if the wires are too long for the signal timing is there anyway to compensate for this.?
     
  6. Aug 13, 2007 #5

    Danger

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    No. If they were too short, you could introduce a delay to compensate, but there's no way to make a signal go faster.
    Unless... I can't see it being practical, but a fibre optic link might be able to make up for lost time. I suspect, though, that the transduction from electronic to optical and back to electronic would negate that.
     
    Last edited: Aug 13, 2007
  7. Aug 13, 2007 #6
    There are several circuit boards in the camcorder, can I extend the line between one of those boards? or do all the wires need to stay original length.:confused:
     
  8. Aug 13, 2007 #7

    Danger

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    I really know nothing about electronics; Berkeman and others of his realm are the ones to answer that. All that I know about it is that when I was doing alarm systems, the length of wire altered the overall resistance of the circuit, which meant that the end-of-line resistor had to be matched to the wire length. I don't know how that principle applies to your case.
     
  9. Aug 13, 2007 #8

    berkeman

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    The wires will be copper. Copper is the best material for electrical conductors like wires.

    My point was that the signals to motors and linear actuators are basically "dumb", meaning that they are low-frequency power signals. If you are lengthening data signal wires, then several considerations come into play, like terminations (back termination or forward termination), and crosstalk becomes a non-trivial consideration. But extending power wires to motors is not generally a big deal, as long as you minimize the voltage drop and power loss in the wires. You can't remote the motor 100 meters away, but you should be able to remote it by a meter without issues. Your warranty is still voided by this -- you know that right?
     
  10. Aug 13, 2007 #9

    Danger

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    Massive admission of ignorance here, Berkeman: what are 'foreward' and 'backward' termination? I've never heard of those terms. :confused:
     
  11. Aug 13, 2007 #10
    Its ok about the warranty. Anything in particular I should do to conserve the power in the wires and minimize voltage drop, I was planning to use one size larger wire like you said before and just solder or clamp on the extra wire.

    thanks.
     
    Last edited: Aug 13, 2007
  12. Aug 13, 2007 #11

    berkeman

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    No, don't say that. Unless you work with high-speed signals a lot, those are terms that wouldn't normally come up.

    Transmission lines are terminated one way or the other to keep reflections and re-reflections from causing ringing in the information signal (which would confuse the receivers and corrupt the data). There are two main themes for termination that I'm aware of:

    Forward Termination -- This is when you put a termination resistance equal to the transmission line Zo at the receiver. That way, the information waveform that travels down the transmission line "sees" Zo along the transmission line, and sees Zo when it hits the input to the receiver. This results in no reflection back up the transmission line. This is what you generally have in most 50 Ohm (or 75 Ohm) systems, like the coax connections between your video components in your TV setup. Also, if you have a multi-drop transmission line (like a circuit board with a digital clock that gets distributed [very carefully] between multiple memory chips or whatever), you need to use the forward termination with the termination resistors at the end of the line, so that all of the multi-drop receivers see a clean signal going by on the transmission line.

    Back Termination -- That's all well and good, but forward terminations burn a lot of power. Driving a few volts into 50 Ohms takes moderate power, way more than you have available with TTL or CMOS logic. There is no way you are going to drive a forward terminated transmission line with digital logic, unless you are using ECL or are pushing AC digital gates pretty hard. So with lower power digital logic, you will usually use a back termination resistor that is placed in series with the line driver output gate, as closely as possible to that driver. You chose the back termination resistance to be the Zo of the transmission line, and subtract the output drive impedance of the drive gate. This presents Zo to any reflected wave coming back up the transmission line, which means that it does not re-reflect back down the transmission line, to cause time-delayed ringing on the transitions of the data waveform. For a 75 Ohm PBC microstrip transmission line, you will probably use about a 50-60 Ohm resistor in series with the transmitting gate, which would have something like a 25-15 Ohm output impedance.

    Good question, Danger. o:)
     
  13. Aug 14, 2007 #12

    Danger

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    It scares the hell out of me to say that after 10 beers I actually understood a reasonable amount of that. At least, I think that I did. If so, then you are referring to the electronic counterpart of an acoustical echo which can be negated by appropriate waveguides?
     
  14. Aug 14, 2007 #13

    berkeman

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    I absolutely dunno about acoustic waveguides. You'll have to post the tips about that. And I've had enough wine to know that I'm done posting anything useful tonight. g'Night, eh!
     
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