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Simple idea but not sure

Discussion in 'General Electronics Discussion' started by jbelectric777, Dec 12, 2012.

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  1. jbelectric777

    jbelectric777

    32
    3
    Nov 29, 2012
    Hi all, I leave my dog out in the back and have forgotten about er, she's a house dog and very small and we dont leave er but long enough to do her business and maybe some sun on a nice day. I have so many components I wanted to run this thru you guys the ones who have the best knowledge,which I wanna say thanks ahead of time. I know I could use a 555 but dont need all that for what i wanna do. I want a capacitor to charge by way of low voltage battery (9v) and a resistor (time and to be determined yet) with a piezo to beep just once real fast then reset, charge the cap again and beep. but like i said i have 555's but dont wanna waste em on somethin so simple. my question is: Is there a component transistor or MOSFET that will pass at a certain level of charge or when there is no charge? I was thinkin a PNP transistor would pass from collector to emitter when the capacitor reached zero or if not zero 1.5v Any idea's? I could buy somethin cheap but its another project at home as well, thanks for any help and for lettn me pick yer brains !!!!!!!:D Jim
     
  2. GreenGiant

    GreenGiant

    842
    6
    Feb 9, 2012
    Would you want it to beep only once or continuously until a reset button is pushed?
    If continuously, how long between beeps?

    You could probably use an old disposable camera, use the circuitry in that and just replace the flash with a piezo sounder of some sort, though there would be some modification to the circuitry to lower the voltage and increase the discharge time of the cap. Shorting the button would give you around 2-3 minutes between outputs.
     
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