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Rating battery for intermittent drain

Discussion in 'Electronic Design' started by Mike Stern, Mar 3, 2012.

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  1. Mike Stern

    Mike Stern Guest

    I am designing a compact signal generator to be powered by a 9V
    alkaline battery. It consists of a transistor (not op amp) phase shift
    oscillator and emitter follower. The output is a square or sinewave at
    60Hz. Draws 12mA.

    Given that the drain is not continuous, due to the waveform's duty
    cycle, how do I estimate the total operating time in hours, assuming
    the battery will provide 500mAH?

    The circuit will function fine down to 6V, with corresponding loss in
    amplitude.

    Mike Stern
     
  2. Jamie

    Jamie Guest

    If you use the math for power in alternating circuits you can get
    close to your figure.
    In sine wave stuff, it would be P = IV*Cos(angle), you do a bunch of
    samples and sum them up.

    for a square wave, it would be 50% of what it would be when on, that is
    is the square wave is 50% duty cycle.

    Watts being a 1J/Sec, so I guess you can accumulate a second of that
    times the duration of your test.

    More on it later I am sure. :)

    Jamie
     
  3. Phil Allison

    Phil Allison Guest

    "Mike Stern"

    ** Completely irrelevant.

    If your meter shows 12mA - that * IS * the battery drain.

    From the data for the Energiser 522 that equates to about 45 hours.

    BTW:

    This kit from Altronics does what you describe and uses only 2mA from a 9V
    battery.

    Output level is constant with frequency and battery voltage down to 6V.

    http://www.altronics.com.au/index.asp?area=item&id=K2544

    Designed by me and published in EA magazine in 1996.

    It will fit in a much smaller box than the one shown in the pic.


    .... Phil
     
  4. Phil Allison

    Phil Allison Guest

    "Jamie = Maynard A. Philbrook
    Fuckwit Radio Ham KA1LPA "


    ** Maynard never has the right answer.

    The know nothing code scribbler is never even close.




    .... Phil
     
  5. Mike Stern

    Mike Stern Guest

    True, true ...

    Mike
     
  6. miso

    miso Guest

    Not to rant, but have you ever compared the capacity of a 9V battery
    compared to 2AA cells and a boost? Basically I hate designs with 9V
    batteries. AA cells are more cost effective. [In any country, you can
    find chickens, AK47 ammo, and AA cells.]

    Basically people snicker at designs that use 9V batteries these days. It
    is not good engineering.

    So is 12ma with no load?
     
  7. Jamie

    Jamie Guest

    Phil, you surprise boy, I gave the correct answer. I gave him something
    to work with. You on the other hand just want to blow smoke because you
    most likely don't know how to break it down.

    Doing power usage with loads of that type requires you to decompose
    the time frame with the signals you are using and load levels they are
    exerting. Those summed together can be used as an average energy use to
    properly calculate the battery life.

    Go blow smoke else where, I don't don't smoke and I don't like smokers
    around me.

    Jamie
     
  8. Phil Allison

    Phil Allison Guest

    "Jamie = Maynard A. Philbrook

    ** It is a totally WRONG answer !!


    ** Battery drain is the AVERAGE current level being drawn - as read on any
    standard amp meter.

    You fuckwit septic twat.



    ..... Phil
     
  9. Phil Allison

    Phil Allison Guest

    "Jamie = Maynard A. Philbrook

    Fuckwit Pycho Radio Ham KA1LPA "
    ** Exactly what I wrote - you fuckwit, septic criminal shithead.



    ..... Phil
     
  10. Jamie

    Jamie Guest

    So what you're saying is, you don't know how to calculate usage at the
    circuit level?

    That figures. any twat, as you say can put a usage meter on the line
    for a reading. But maybe you have forgotten something? This is an
    engineering area, not a fucking class room on how to use your amp meter.

    Go back and play with your boom boxes.

    Jamie
     
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