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Need help with 24V and switch

Discussion in 'General Electronics Discussion' started by David_M, Apr 3, 2013.

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  1. David_M

    David_M

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    Apr 3, 2013
    I have a quick question. First off I am new and building a full size R2D2 from Star Wars and am needing a bit of help with one part of my electronics. I am running 2 x 12v 18Ah batteries in series. I need a switch that can handle 24v at 10A load. The switch I wanted to use is shown in the picture. Can I use a switch that is made for 12v on a 24v circuit? I am aware that there is an LED in the switch, but I intend on adding a resistor in line on the negative side.

    Any help is appreciated.

    [​IMG]

    [​IMG]
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    If the switch is rated for 12V, then it is probably not rated for 24V (or they'd just say it).

    A detailed datasheet for the switch may tell you more, presuming you can find one.
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    The datasheet says 12v, so it's 12V, not 24V.
    at lower current (e.g. only 10A instead of the rated [email protected]) you may be able to use it with 24V. And you need to limit the LED current, as you have observed.

    Since you already have that switch, give it a try.
     
    Last edited: Apr 3, 2013
  4. Electrobrains

    Electrobrains

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    Jan 2, 2012
    I suppose you will be able to use the switch without greater problems.
    Just be aware of your full responsibility and the lack of warranty.

    The rated data for a switch will assure a certain amount of switch cycles for a specified load (here probably the rated DC voltage and current with a resistive load).

    If you exceed the rating (higher current, higher voltage, inductive or capacitive load, temperature etc), you will reduce the life expectancy of the switch.

    When exceeding the voltage rating, you will get higher energy sparkles in the contact gap, that will burn your contacts and in worst case give you an all-destroying arc that also could cause fire.
    In general it's difficult to switch high voltage DC current, especially if you have an inductive load. For higher voltages (>40V), also the isolation matter should be considered.

    When exceeding the current rating, you will also burn the contacts more quickly and get a risk of welding them together.
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    no you dont, looking at the diagram on the switch packet indicates that a series resistor for the LED is built into the switch :)

    Dave
     
  6. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Yes, I saw that. This resistor is with a probability of 99.9999% designed for 12V operation. So it's a good idea to add some more for 24V operation.
     
  7. David_M

    David_M

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    Apr 3, 2013
    The way I am going to be using this is to break the circuit from my motor controller. There will never be any current flowing through the switch when I turn it on or off. This is just to protect my sabertooth motor controller in case of a dead battery.
     
  8. David_M

    David_M

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    Apr 3, 2013
    I've contacted the manufacturer for the data sheet
     
  9. David_M

    David_M

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    Apr 3, 2013
    What could work is that I could have the switch on 12V and have it turn on a relay at 24V, but I have not been able to find a 12V/24V relay that does not draw a lot of power to keep it turned on
     
  10. Electrobrains

    Electrobrains

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    Jan 2, 2012
    If you never switch under load and don't have more current than specified, I suppose that switch will work very well.
     
  11. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Latching relays don't need any current to keep them in either state.
     
  12. David_M

    David_M

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    Apr 3, 2013
    Please forgive me, what is a latching relay? I am very new to electronics
     
  13. Electrobrains

    Electrobrains

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    Jan 2, 2012
    latching relay
     
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