Rocker Switches?

Discussion in 'Instruments / Avionics / Electrical System' started by pequeajim, Sep 5, 2007.

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  1. Sep 5, 2007 #1

    pequeajim

    pequeajim

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  2. Sep 5, 2007 #2

    wally

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    Hi,
    Those lighted switches in your link will probably not have the right voltage lights. The are most likely 115Vac.

    As far as the switch actuation and current rating, they would probably work ok, just keep in mind what the consequences will be if/when they fail to turn on or fail to turn off or open unexpectectedly. What I am suggesting is, don't use for critical functions like a boost pump.

    The automotive accessory industry might have some and they will most likely be 12V lights too.
    Best wishes,
    Wally
     
    Last edited: Sep 5, 2007
  3. Sep 5, 2007 #3

    pequeajim

    pequeajim

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    Good catch Wally. I didn't think about the voltage of the lamps.

    I'll check some of the auto parts distributors. $40.00 a pop for this kind of switch from Gulf Coast is a bit pricy for my taste. That's why I am looking for an alternate source.
     
  4. Sep 5, 2007 #4

    Waiter

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  5. Sep 5, 2007 #5

    Captain_John

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    Jim, Wally (of course) is right!

    I didn't notice that you were looking for lighted ones!

    :nervous: CJ
     
  6. Jan 4, 2008 #6

    CESSNADON

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    This post may be a little late but I wanted to respond just in case you haven't selected your rocker switches.

    I'd check Allied Electronics or any of the many other electronics components suppliers. The most important thing you will want to know is What the DC rating of the switch is and how much inrush current can it handle. DC behaves much differently than AC when it is being switched. The AC current passes through zero volts and current every cycle while DC voltage and current remain constant. What this means is when you switch AC ,the zero crossing of the voltage and current reduce the arc between the switch contacts, while when you switch DC the current remains high until the contacts are far enough apart to quench the arc. In some cases, when switching DC the arc will not extinguish between the contacts and you end up with a burned up switch. What all of this means is that a switch rated for 20a at 120vac may only be rated at 5a at 50vdc or not DC rated. If you find a line of switches that you like, go the manufacturer's website and check the specs.
     
    Last edited: Jan 4, 2008
  7. Jan 5, 2008 #7

    Midniteoyl

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    The same switch is rated lower for DC due to heat...
     
  8. Jan 6, 2008 #8

    CESSNADON

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    When the switch contacts are closed, the resistance is essentially zero so they are in effect a continuation of the electrical conductor. I don't believe that one uses different wire sizes depending on wether you are using AC or DC...Any heat that is generated in the switch is caused by the arcing of the contacts when the switch is actuated.
     
  9. Jun 11, 2009 #9

    Alan Waters

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  10. Jun 11, 2009 #10

    Dan Thomas

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  11. Jun 11, 2009 #11

    Midniteoyl

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    Not sure what your saying here? The article you linked to had both arcing and heat as limiting factors....

    Here's the thing, though. You cannot used a AC switch rated at, say, 5 amps in a DC circuit at 5 amps. Because of the polarity change in AC described above, the current is not constant and will go to zero. While it is there, and in fact anywhere less than peak, it is drawing less current and thus less heat. If you put that AC switch in a DC circuit, it will overheat and melt waaayy before the contacts get eaten up.
     
  12. Jun 12, 2009 #12

    Dan Thomas

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    AC is measured in RMS values, with the reading we see being equivalent to DC flow. 110VAC, for instance, is not 110 volts peak-to-peak on the sine wave; it's closer to 170 volts and the current at that point is higher than the current at the RMS value. So the load on the contacts, in terms of heat, is the same.

    The makers of high-powered stereo equipment love to play on the ignorance of buyers. They talk about 100 watts of output, "peak-to-peak," which is the clue that they've fudged the specs. The RMS on that would be around 50 watts, max, which is what an honest maker would say. Lowering the voltage by a third will also drop the current flow by a third, and the result is about 50% of the original, crooked claim.

    See What is Alternating Current?

    An excerpt from that:


    • Amplitude. Another thing we have to know is just how positive or negative the voltage is, with respect to some selected neutral reference. With DC, this is easy; the voltage is constant at some measurable value. But AC is constantly changing, and yet it still powers a load. Mathematically, the amplitude of a sine wave is the value of that sine wave at its peak. This is the maximum value, positive or negative, that it can attain. However, when we speak of an AC power system, it is more useful to refer to the effective voltage or current. This is the rating that would cause the same amount of work to be done (the same effect) as the same value of DC voltage or current would cause. We won't cover the mathematical derivations here; for the present, we'll simply note that for a sine wave, the effective voltage of the AC power system is 0.707 times the peak voltage. Thus, when we say that the AC line voltage in the US is 120 volts, we are referring to the voltage amplitude, but we are describing the effective voltage, not the peak voltage of nearly 170 volts. The effective voltage is also known as the rms voltage.
    Dan
     
  13. Jun 12, 2009 #13

    Midniteoyl

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    Sorry Dan.. I know. Electronic Tech here... Radars, Sat Com, Computers, CNC's, Phase Converters, you name it. :)

    Fact is, A/C runs cooler than DC, volts and amps (power) being equal. Its the same for A/C motors: they run cooler than DC motors.

    Is the arc across the gap larger in DC? Sure... but the main reason you cannot use a 24v AC switch in a 12v or 24v DC circuit is heat. You could get away with using on rated with, say, 3-4x the amp rating, but then you'll run up against that 'arcing' thing and it prolly wont last as long as you hope. And that whole thing about there being no resistance at the contacts? Crap... there is. There always is. Thats why splices suck compared to running a new line.

    Not trying to start a debate, however... My original intent was to point out an obvious reason why you cannot just assume just any 'ol switch will work.
     
  14. Jun 12, 2009 #14

    Midniteoyl

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  15. Oct 26, 2009 #15

    Sticky1

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    There are many manufactures that make switches. If you are not in a rush.....look at avero rocker switches. The US dist. is in the mid west and is a decent guy. The owner is an ass!
     

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