Help with calculating Hz in siren curcuit

Discussion in 'General Electronics Chat' started by SainAralor, Oct 9, 2016.

  1. SainAralor

    Thread Starter New Member

    Oct 9, 2016
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    Hi! Could anyone help with how to calculate Hz in a siren system? Here is a picture of the system:
    SainAralor_schematic.jpg

    The Hz of the first astable 555 circuit is supposed to be 1 Hz and the other system is supposed to be 1kHz.

    I used this formula:

    SainAralor_calcutations.gif

    (the one on the top called "to calculate frequency")

    I tried to put 3.3u as the c value and 0.01u (converted to Farad of course). I also tried to put both in series and in parallel, but i couldnt get 1Hz!

    What am i doing wrong here?

    All help much appreciated, and thanks for your time!

    Moderators note: replaced unwanted links with uploaded pictures
     
    Last edited by a moderator: Oct 9, 2016
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    481 Hz central frequency, it will sweep up and down at 1hz rate...
     
  3. SainAralor

    Thread Starter New Member

    Oct 9, 2016
    2
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    Could you explain that a bit? Sorry i'm quite new to this :)
     
  4. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Please provide a 'clean' link! -- Speaking for myself, I have no desire to join another site nor expose myself to their spam, etc. merely to view your images/'outside' post{s}! Advice and instruction are offered gratis here - inasmuch as basal courtesy (on your part) costs nothing!

    With regards
    HP
     
    Last edited: Oct 9, 2016
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    @Hypatia's Protege ,
    I always use adblock to block unwanted adds.
    I have replaced the links with uploaded pictures.

    Bertus
     
    Hypatia's Protege likes this.
  6. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    @SainAralor
    For the benefit of other readers I've done your work and posted the image (below):

    GjirEog.jpg

    What would you have us clarify? The second stage's 'control voltage' input (and, hence, output frequency) is 'swept' by the first stage...

    With regards
    HP
     
  7. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Thanks @bertus -- I made my second response prior to seeing your amendment to the OP:oops::)

    Best regards
    HP:)
     
  8. Aleph(0)

    Member

    Mar 14, 2015
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    HP that brings back memories for me cuz when I was a kid I used switched DC levels on pin 5 of astable 555 for FSK generator and it ran error free at 19.2k baud with just ps osc cap but I had ten pole RC LPF on output! Now everyone is probably saying I was super industrial strength stupid for not just using XR2206 with onchip digital keying circuit and sine output:oops:! So I was just having fun building RS232 to FSK translator w/o special chips:)
     
  9. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    The main frequency astable is centerd on 481hz, without the 1 hz astable it would make a continuous tone, the second astable is clocking at 1 hz and increases and decreases the 481hz, so it may sweep from 400hzto 600hz due to the control voltage on pin5.
     
  10. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Go figure!;););):p

    TTFN
    HP:)
     
  11. ci139

    Member

    Jul 11, 2016
    341
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    Random_555_TmrCalc.png
    Random_555_TmrCalc~.png
    blaah, blah , . . .
     
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