Stepping up 3V to 16V

Discussion in 'General Electronics Chat' started by ygd, Jun 16, 2010.

  1. ygd

    Thread Starter New Member

    Jun 16, 2010
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    I've been trying to create a little alarm system that goes off whenever you break a beam of light. My project runs on 3V but it's not very loud. My piezzo buzzer can take up to 16V. How can I step up 3V to anything higher than 9V (all the way up to 16V) without using more than one pin on the AVR I'm using for this project?
     
  2. SgtWookie

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    Jul 17, 2007
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    No mention of the current requirement of the buzzer?

    That's kind of important.
     
  3. ygd

    Thread Starter New Member

    Jun 16, 2010
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    Current is 7 mA max at 12V.
     
  4. SgtWookie

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    Jul 17, 2007
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    See the attached; give it a shot.

    You can probably get everything from a Radio Shack store, if you're in the States.
     
  5. ygd

    Thread Starter New Member

    Jun 16, 2010
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    I'm trying to use as few components as possible. Are there any IC or transistor solutions with minimal additional parts?
     
  6. SgtWookie

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    Jul 17, 2007
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    I thought that's what I gave you. :rolleyes:

    You could delete R2 and C2, but you will reduce battery life.

    R1 is mandatory, as is Q1, L1 and D1.

    You could eliminate C1 and rely on the capacitance of the piezo, but I don't know what that is. It probably is not much.

    D4 is for safety. Without a load, the output voltage would climb until things started frying.

    Rload is your piezo buzzer. You could eliminate it, but I thought that was the whole point of the thing.

    Maybe you thought you could add just one part? If so, Digikey has a number of DC-DC converters. They'll cost you anywhere from $20 to $200 plus shipping. You can build the thing I posted for lots less than that.
     
    Last edited: Jun 17, 2010
  7. ygd

    Thread Starter New Member

    Jun 16, 2010
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    Is there any way to do it with this part.
     
  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    Sure there is, but you will need many more components than SgtWookies design.

    Just look at around page 9 of the datasheet for the device to see circuits built with the device. You will see the other components required to make that IC step-up.

    [​IMG]

    Here is the datasheet for the MC34063A.
     
  9. SgtWookie

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    Jul 17, 2007
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    Something that might not be obvious in the schematic I posted, is the AVR output pin needs to output a 250kHz 50% duty cycle square wave to switch the transistor; or a square wave that is on for 2uS and off for 2uS. I'm not familiar with AVR's, but if they have a PWM function, this might be a good time to use it.

    Don't leave the output pin high for more than a couple of microseconds, or you will get very high current flow through R2, the inductor and transistor. R2 will act as a cheap fuse and burn up if you have the transistor on for too long.
     
  10. ygd

    Thread Starter New Member

    Jun 16, 2010
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    What about just adding a battery between the AVR and the buzzer?
     
  11. SgtWookie

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    Jul 17, 2007
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    You could do that.

    You could switch the ground side of the buzzer using an NPN transistor.
    The battery would be connected to your AVR ground and the buzzer +
    Connect an NPN transistor's collector to the ground side of the buzzer, the emitter to GND.
    Use a 1k resistor from the AVR I/O pin to the base.
     
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