Realistic siren sound schematics.

Discussion in 'The Projects Forum' started by Brian203707, Mar 27, 2010.

  1. Brian203707

    Thread Starter New Member

    Feb 13, 2010
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    I have searched so many sites and have managed to duplicate the fire truck and ambulance siren, but does anyone have the schematics for the yelp, and the hail 1 and hail 2 for the US police sirens? With 2 lm555 timers in a sweeping output frequency schematic I was able to emulate a realistic sounding slow siren and up and down ambulance but I cannot get it to do the fast smooth rotating police sound. The only yelp schematic I have found uses unijunction transistors and I cannot find those anywhere.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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  3. SgtWookie

    Expert

    Jul 17, 2007
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    Digikey carries 2N6027 and 2N6028 UJT's (PUT's, actually - Programmable UJT's) for $0.48/ea. The 2N6028's carry more current [eta] than the 2N2607's do.

    [eta]
    Newark carries a few different UJT's:
    http://www.newark.com/jsp/search/br...e=en_US&catalogId=&prevNValues=500003+1001821

    Avoid NTE parts unless you like spending far more than you should.

    I don't know what Newark's handling/shipping charges are lately, and I don't know if they'll ship USPS 1st Class like Digikey will.
     
    Last edited: Mar 27, 2010
  4. Wendy

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    Mar 24, 2008
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    [​IMG]

    A really old design I copied when I was a teen.
     
  5. beenthere

    Retired Moderator

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  6. Wendy

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    Mar 24, 2008
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    I have another sheet with a very similar schematic, that has a list of substitutes I tried. To be honest I thought that was the one I used in the original forum long long ago (this was a recycled picture).
     
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