Beginner help with DIY siren project.

Discussion in 'General Electronics Chat' started by danger, Sep 5, 2010.

  1. danger

    Thread Starter New Member

    Sep 5, 2010
    11
    0
    I am a total beginner at DIY electronics. Starting a project and hoping to learn more. I have some questions....

    Here is the schematic for my project....

    http://www.jacoblysgaard.com/wp-content/gallery/dub-siren/3137510536_811c39266b_o.jpg

    I have everything I need to begin, but atm I am in the process of trying to fully understand the schematic. Then I intend to do a drawing of my board layout.

    I am having difficulty understanding the power source and ground. Since this is a DC circuit, how and where do the + vs. the - wires physically get connected to the circuit? Where exactly do I connect all the grounds to? I understand all the places where the schematic calls for a connection to the power source. I'm just having a hard time visualizing it.

    Any help would be greatly appreciated! I may have more questions too!:)
     
  2. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    All 6 of the points labeled +9V tie together and go to The positive terminal of your 9V battery or power supply. 2 other points are labeled Vcc, They should also connect to those 6 points labeled +9V. Vcc is just another way of saying power source +.
    There are 8 ground points labeled on the schematic. They should all be tied together and go to the negative terminal of you 9V battery or power supply.

    I hope your project is fun and entertaining.
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,534
    555 circuits are easy mostly. The first is a simple oscillator, the second 555 is a voltage controlled oscillator. You want something simple, try one of these...

    New Guy Here - Wanting to build Siren

    [​IMG]

    If you do a search you will find this site is full of similar threads.

    As to understanding the 555, I'm working on a set of articles...

    The 555 Projects

    The 555 is a very versatile chippie.
     
  4. danger

    Thread Starter New Member

    Sep 5, 2010
    11
    0
    Wow, thanks for the quick replies! Very helpful!
     
  5. danger

    Thread Starter New Member

    Sep 5, 2010
    11
    0
    Can someone please help again. I am working on the +output where it calls for a 10uF capacitor shown on the schematic from my first post. I have a 10uF capacitor, but it is ceramic and it does not show any polarisation on the actual capacitor. Do I need a different capacitor? Or will this one work? The schematic obviously calls for a polarised 10uF cap.

    Also, I'm wanting to put a resistor between this cap and the final +output to tame the output volume a bit. What ohm resistor should I attempt using?
     
  6. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    Your 10 uF non-polarized capacitor is even better than the polarized one shown in the diagram. I've never seen a 10uF ceramic cap.
    The 50k pot ahead of that cap is the volume control. It goes from zero to almost max available output. It's almost max because the 10k resistor ahead of the pot forms a voltage divider with the pot so you don't quite get full output. If you still want to limit the maximum volume, increase the value of that 10k resistor. You'll have to experiment to find the volume you like.
     
  7. danger

    Thread Starter New Member

    Sep 5, 2010
    11
    0
    Thank you JJ! You've been a great help!

    Yes everything I've read about capacitors suggests that the ceramics above 1uF are not common and only find use in few applications(x-over circuits?). But I've read they exist up to 30uF.
     
  8. tc684

    New Member

    Oct 10, 2010
    1
    0
    I've recently started to build this siren and I am OK with most of the theory behind the circuit but I was wondering what purpose the 50k variable resistor serves that feeds back into the VC on IC1 and then into IC3. I can see that the output signal of IC1 is sent to the op amp but what effect is the other voltage having on IC1? Basically what is the 50k variable controlling and what effect is it having on the output of IC1.

    Thank you for any help.
     
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