Make a buzzer sound at a certain time with a potentiometer?

Discussion in 'General Electronics Chat' started by Fuji, Jan 13, 2015.

  1. Fuji

    Thread Starter Member

    Nov 8, 2014
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    I was thinking of a simpler way to make a buzzer sound at a given time. For example, using a potentiometer to set the time to 1 minute, 5 minutes, 13 minutes, 22 minutes etc. Once the time has reached, the buzzer will sound.

    Does this need a microcontroller for this to operate? What alternatives are there for this idea? Perhaps counters? If so, what would be a good counter for this buzzer to sound at a given time?
     
  2. crutschow

    Expert

    Mar 14, 2008
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    If you want the time to be somewhat accurately set, then you will likely need a micro to control it and input the time with a keyboard.
    Or buy a kitchen timer. ;)
     
  3. Fuji

    Thread Starter Member

    Nov 8, 2014
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    Well if thats the case, I'd just go along with using a PIC10F200. Is it that when twisting the potentiometer, I assume depending on the voltage level that it would make the buzzer sound?
     
  4. ErnieM

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    Apr 24, 2011
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    Since your sole input is a potentiometer there really is not an accurate way to adjust this thing. So how accurate do you want it?

    I don't see any compelling reason to use a micro on this. Something like a CMOS timer similar to the MC14541B could do the job to adjust the timeout over a 22:1 range.
     
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  5. gerty

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  6. Fuji

    Thread Starter Member

    Nov 8, 2014
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    Well, what would be your alternative or better component to use instead of a potentiometer? separate buttons for different timings?
     
  7. MagicMatt

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    Sep 30, 2013
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    Basic 555 Timer and a simple buzzer? Simple single pole 5 way switch to select preset Capacitor/Resistor pairs... or as you say, use a Pot and mark a few positions.

    PIC is overkill for this, as much as I love them. If I were using a PIC I'd want a display to watch the countdown too... then I'd want at least 3 buttons for reset, start/stop, add minutes...

    Depends if you want to go basic and old skool, or all fancy and start using blue LEDs... ;)
     
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  8. ErnieM

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    Apr 24, 2011
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    HOW I would do something depends on WHAT I am doing.

    You state your range, resolution, and accuracy and I will give a way/ways to do it.

    Here is a timer I made that is in the public domain.

    I've also made timers that live inside some MIL-PRF relays. While I can't provide the schematic (I don't own it) I can answer lots of questions.
     
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  9. Fuji

    Thread Starter Member

    Nov 8, 2014
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    Thanks for the reply. I actually thought of using a 555 timer, BUT my buck boosts out around 2.5 volts. It's not enough to power the 555 timer. I don't recall how many volts a CMOS 555 timer would turn on. I assume lower voltage?

    My idea was basically a count down timer. So basically if I was to set the time at 15 minutes (Position 1 of the potentiometer), the buzzer doesn't go off until 15 minutes has reached etc.. 30 minutes (Position 2), 60 minutes (Position 3)....
     
    Last edited: Jan 14, 2015
  10. ErnieM

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    Apr 24, 2011
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    CMOS logic chips will need 3V and above to work. There are some micros that work down to 2V but then you have the problem of finding a buzzer that buzzes at 2.5V.

    Any '555 based timer has the problem of needing a large value cap with very small leakage, as the time interval is based around one RC time constant. Devices like the MC14541B use an oscillator driving a digital counter to get long times with smaller (and cheaper) caps. That is what the customers orgionally used in those MIL-PRF relay timers (or a close similar chip, the number & data sheet doesn't strike the mental bell hard so I'm not 100% sure it is what was used).
     
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