0.5 Volt Trigger Switch.

Discussion in 'Off-Topic' started by YFZR750, Oct 2, 2014.

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  1. YFZR750

    Thread Starter New Member

    Oct 2, 2014
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    Good Day Everyone,

    New to the forum and need some help.

    I would like to pulse 12v Dc at specific frequencies for a project.

    I would be using my PC as a sound generator to provide the frequencies.
    But it only pushes out 0.5 to 0.8 volts.

    So I wanted to know if there's a possibility that I could build something that can be triggered by the 0.5 volts to open a switch for 12v to be switched on and off as the frequency pulses.
    And it would be low frequency, around 50hz but I would like to go to 20 000hz if I need to.

    Thanks
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    A biased NPN bipolar transistor, where the base bias is set to 0.4V. A capacitively-coupled o.5Vp-p signal can drive the base to turn-on and turn off.
     
  3. YFZR750

    Thread Starter New Member

    Oct 2, 2014
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    Out of all the forums I've been on, that was by far the fastest reply I had.

    Anyway, I am not very good with electronics so I do not fully understand what you just said.

    Will this do what I need without it possibly blowing my sound card?

    And do you perhaps have daigrams on what parts are needed and how to arrange them ?

    Many thanks
     
  4. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    hi YF,

    Look up germanium transistor, Vbe ~ 0.2V

    E

     
  5. wayneh

    Expert

    Sep 9, 2010
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    Another approach would be to feed your output thru a comparator such as LM339 (4 comparators in one IC), and use the output of the comparator to drive a MOSFET switch. This approach would help keep a nice square wave shape, since the comparator will switch hard from one state to the other.

    You would feed the comparator an adjustable voltage "reference" to compare the PC output voltage to, and this will define the voltage where the comparator transitions from one state to the other.
     
  6. ScottWang

    Moderator

    Aug 23, 2012
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    Using an ac non-inverting op amp to amplifying the input signal and the output of op amp adding a diode and capacitor to do a half wave rectifier and filter to drive a mosfet, the mosfet can be a output or you want the mosfet to drive a relay.
     
  7. YFZR750

    Thread Starter New Member

    Oct 2, 2014
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    This is getting a bit too complicated for me to handle.

    I have built a diode bridge to convert AC to DC and that was kind of easy.

    Is there any way for me to build up a simple device with parts I could get from the electronics shop?

    If not, would it be possible I could step up the frequency voltage to 12v ? Using a second source of power would not be a problem.

    Also, The program on my pc alows me to choose between sine, square, sawtooth frequency and I would like it to be able to do something if I change the settings.

    Many thanks
     
  8. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Stare at this. It turns on for the positive parts of the soundcard waveform...

    68a.jpg
     
  9. YFZR750

    Thread Starter New Member

    Oct 2, 2014
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    Hi, is it possible to modify it to do both positive and negative? Exactly as the frequency the pc will put out?

    Thanks
     
  10. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Well, then you dont want pulses; you just want a linear amplifier.

    So what do you really want? A linear 12Vdc powered amplifier, where the output is biased to 6V, and where the output swings to near +12V when the soundcard output is at 0.5V, and where the output swings to near 0V when the soundcard output is at -0.5V?
     
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I second Mike's suggestion (post #2).
    The circuit would look something like this:
    SimpleAmp.gif
    What are you proposing to drive with the pulses? Do you mean square pulses?
    Do what? Change which settings?
     
  12. ScottWang

    Moderator

    Aug 23, 2012
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    Vin → Capacitor(c1) → non-inverting op amp(Gain=20) → diode and capacitor(c2) → N-ch mosfet

    diode : 1N4148.
    C1 about how high the frequency you want to pass.
    C2 is the transfer time from AC to DC how long you want to keep.
    google "non-inverting op amp".
     
  13. YFZR750

    Thread Starter New Member

    Oct 2, 2014
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    I would like to power a fuel cell that converts water to Hydrogen and oxygen by means of electrolysis.

    As theory goes, a certain frequency makes the molecules resonate. Making them easier to split.

    I am not sure of the frequency, as it could be between 10 to 20 000hz.

    So as I experimented 0.7 volts from the pc is not enough to do anything even if converted to DC. So I would Like to step up the voltage to see if it could work with the frequency coming from the PC.

    Please don't tell me it won't work, I am curious and would like to see for myself if it could work.

    Hopefully it would clear up the confusion.

    Thanks
     
  14. YFZR750

    Thread Starter New Member

    Oct 2, 2014
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    Just to make it simple, I want the exact frequency from the PC but at a higher voltage.

    Thanks
     
  15. YFZR750

    Thread Starter New Member

    Oct 2, 2014
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    Voltage I'm aiming for is around 100 volts. But I would first like to try 12 volts to see if anything is produced.

    Thanks
     
  16. MrChips

    Moderator

    Oct 2, 2009
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    Whoa! Jumping from 12V to 100V is a huge step.

    For 12V you can use a single NPN transistor such as 2N3904 or 2N2222.

    For 100V, I would use two stages, such as 2N2222 followed by TIP47/48/49/50
     
  17. YFZR750

    Thread Starter New Member

    Oct 2, 2014
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    Hi,

    Could I use a secondary power source for it? As I do not want to draw too much power from the pc as it could blow the sound card.

    If so, do you perhaps know of a diagram for the wiring ?

    Thanks!
     
  18. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    I will be extremely surprised if any frequency out of a sound-card will have any effect on a water molecule. The resonance frequency of a water dipole is order of magnitudes higher...
     
  19. YFZR750

    Thread Starter New Member

    Oct 2, 2014
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    Okay, what would you reccomend me trying ?
    I am also learning so I am open to suggestions.

    Or could I give it a shot and see if there's a possiblity that it could work?

    Because its not just the resonance, the resonance is done at 0,5 volts but there's just not enough power to complete the electrolysis.

    Thanks
     
  20. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Lets have a reality check: If applying any AC frequency across the electrodes of an electrolysis cell made the process more efficient, wouldn't the companies that do this commercially be doing it???
     
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