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Conversion of 24V airhorn to 12V

  1. Mar 31, 2012 #1
    Would anyone know how to install a 24V airhorn I found at a garage sale in my truck? Obviously I only have a standard 12V battery as a power source... Thx in advance, and easy on the mockery, I am not a mechanic or an electrician by any means...
  2. jcsd
  3. Mar 31, 2012 #2


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    Since it probably isn't going to produce much noise at 12V, you have a couple of choices...

    1 ... A bit extreme bout you could series up another 12V battery and have that 24V feeding the airhorn
    2. ... A better way would be looking at a boost DC to DC voltage converter to produce 24V from the 12V supply.
    The only prob I could see with this way would be finding a DC to DC converter that can supply the current required by the airhorn. It could easily be 5 or more Amps

    Some google searching would probably lead you to somewhere that sells such modules
    Does the airhorn have an info label on it ? saying..... 24V at xx Amps. ?

  4. Mar 31, 2012 #3

    jim hardy

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    Those things in my day were not very sophisticated. Open it up and see how it works.

    Usually they are a vibrating diaphragm with moving contact that interrupts current to an electromagnet when the diaphragm moves.

    The strength of the electromagnetic pull is in proportion to the current
    and inverse proportion to the air gap.

    It may well have too much air gap to work at 12 volts (half current)
    often there's a nut and setscrew someplace that controls airgap. Sometimes you bend a piece of the electromagnet's structure.
    experiment with that concept of adjusting airgap for satisfactory sound at lower voltage.

    Worst case you'll have to re-wind the elctromagnet with wire about three gage numbers larger.
  5. Mar 31, 2012 #4


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    This could involve re-winding the coil with 1/√2 of the original number of turns. Removing the original could be a problem if it's potted in something very tough, though.
    I have come across air horns with a compressor motor in them. Rewinding that could be a lot of hassle.

    If you wanted to use 24V, then an extra battery and a 12-24V converter with low peak power but could recharge 24V worth of battery, which could supply the 10A or so when the horn is active.
    I guess the price for the 24V horn was attractive as 24V is much less common in domestic vehicles.
  6. Mar 31, 2012 #5
    When I was in college in the late 60s, a friend of mine had a similar problem. He owned an old jalopy with a 6 volt electrical system and bought a 12 volt tape deck to woo the girls. He asked me for a circuit to allow him to use the 12 volt tape deck with the 6 volt system. I drew up a circuit that would charge two 6 volt batteries in parallel but which could be switched into a series circuit when he was with a girl. Ultimately he rejected the idea and bought a 12 volt battery which he charged with an ordinary battery charger.

    I think you could buy a small 12 volt battery and a small 12 to 24 volt convertor. Hook the second 12 volt battery in series with the battery you have and use the 12 to 24 volt convertor to charge it. Since the duty cycle of the air horn presumably will be very low, you can charge the second battery slowly requiring only a small DC/DC convertor.

    Edit: Sophie, I didn't see your post before I posted mine. I guess we think alike.

    Edit: I once read about a military surplus device that took a 12 VDC input and provided a 12 VDC output. So what good was it? The output could be connected in series with the input to get 24 VDC.
    Last edited: Mar 31, 2012
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