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Adding a timer to a siren

Discussion in 'General Electronics Discussion' started by Magoogle, Feb 18, 2013.

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  1. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    Hey electronic people!

    Got a question. On this alarm diagram I was looking at they use a capacitor to keep the siren charged even after the power is cut. However they used several other components that i don't need.

    Basically I have a 12V wireless controller which is connected to a tilt switch which is connected to a siren. When someone lifts my motorcycle off its kick stand the siren sounds. When it is layed back down the siren turns off. Something nice and simple for a motorcycle alarm. However I would like to make the siren continue to stay on for a period of time even after the bike has been put back on the kick stand.

    Anyone have specific circuit that would work in line with the siren?

    Thanks!
     
  2. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
  3. donkey

    donkey

    1,293
    56
    Feb 26, 2011
    how long you want it to go for? i got an old alarm circuit that has only 2 ways of disabling it, put a key in and turn it of or unplug its power (I put it in a tin and glued it close so getting to the battery would be kinda hard)
    oh also what other features you don't want? you need to be very precise with alarms as you will be the one that is losingitems if its not what you need.
    how long does the siren go for?
    how is it powered? if you use the bikes battery and leave for a few days and a possum (or your countries equivalent) bumps it then you will come home to some very angry neighbours who didn't sleep for 3 days and a flat bike battery.
    is a tilt sensor all you want? or do you want to upgrade and haveit so if anyone touches your throttle it will sound(thats harder but very possible) the list goes on. I understand for alot of people bikes are a way of life and if in your case that is the case I really want your pride and joy to be well looked after
     
    Last edited: Feb 18, 2013
  4. Merish

    Merish

    1
    0
    Feb 18, 2013
    You can design a simple one-shot 555 circuit that is activated when the switch is tilt.
     
  5. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    This is what i have so far:



    When the bike returns to its tilted position the alarm stops. However if a thief is smart enough than they could realize this and push the bike out at an angle. I want to add some way to keep the alarm sounding for a at least 1 minute long, and possibly with the ability to change the timer if needed. The device is directly connected to the bikes battery. Its very hard to reach the bikes battery.
     
  6. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    So I just need to find what capacitor for the 555 to enable it for 1 minute before it cuts off.
     
  7. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    from what I can find, if im using the calculator right it says if i use a 470uF capacitor and a .20ohm resistor for R1 then the siren should sound for about 103 seconds. Which would be acceptable. What you guys think?
     
  8. john monks

    john monks

    693
    2
    Mar 9, 2012
    470uf capacitor will help increase the time. Also I would try adding a 100kohm resistor in between Q2 base and the capacitor. Then I would decrease R3 to 100 ohms. Then decrease R2 to 470 ohms. This should give you over a minute of sound.
     
    Last edited: Feb 19, 2013
  9. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    ok so u lost me with the Q2 thing. I have never used a 555 so this is the diagram I am working with. help me fill in what your talking about.
     

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  10. Magoogle

    Magoogle

    62
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    Jul 31, 2012
    also need to make sure this circuit will work with a switch that is not actually momentary. I'm using a mercury tilt switch so it might be momentary or it might not, depending on what the thief is trying to do.
     
  11. john monks

    john monks

    693
    2
    Mar 9, 2012
    If you use the 555 timer the the time will be .693 X R X C. In other words if you use a 100k resistor and a 100uf capacitor your time will be about 6.93 seconds. Maybe you will want to use a 1000uf capacitor for 69.3 seconds.

    My earier proposal simply suggested changing the value of some parts and adding one resistor.

    Maybe you should try both and seeing which way works best.
     
    Last edited: Feb 19, 2013
  12. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    does the wattage and voltage of the resistor or capacitor matter?
     
  13. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
  14. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
  15. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    Also im alittle confused by your calculations.. how did you come up with 69.3?

    .693 X 100,000 X 1000 = more than 69.3?

    Sorry if these are dumb questions..

    http://www.csgnetwork.com/ne555timer1calc.html is the time calculator i was using.
     
  16. john monks

    john monks

    693
    2
    Mar 9, 2012
    I got my figures from the 555 datasheet.

    I didn't mean to confuse anyone. Of course you will have to use a relay.
    I was presuming you would add the 555 into the circuit you already had. But if you didn't the you would have to add a transistor and a relay capable of handling the amperage rating of your siren. I would look at using a IRF510 MOSFET with a relay. And the relay should have a protection diode in parallel with the coil of the relay. And the diode should be reversed biased when the relay is energized.

    I can't find the datasheet for the GP-01 but I found a different similar car siren and it draws 255ma. If yours is similar you should be able to drive it directly from a IRF510 or similar MOSFET with no relay.
     
    Last edited: Feb 19, 2013
  17. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    That's 0.693 * 100,000 ohms * 1000 *micro* farads

    so 0.693 * 100,000 * 1000 / 1,000,000

    And that's 69.3

    However, with this resistor and capacitor combination you may find that the timer period is considerably greater than 69.3 seconds, or possibly fails to oscillate at all in some cases.
     
  18. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    blah somethings wrong, Im testing this with an LED for now before i wire it up to an annoying siren.. the LED remains lit all the time with the switch closed..? But if you open the switch its solid for a few seconds then like for 1 or 2ms its dark.. almost like a blink and it continues to do that..?
     
  19. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    OK so had a resistor in a wrong place and forgot to add the 0.01uF capacitor.. so now when I provide power with the switch in the open position the led remains off. And when I turn the switch closed the led lights up but remains lit indefinitely.
     
  20. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    ok well im stumped..
     
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