low battery cutoff ltspice

Discussion in 'The Projects Forum' started by j4e8a16n, Mar 14, 2014.

  1. j4e8a16n

    Thread Starter Member

    May 1, 2013
    33
    0
    Hi,

    I found that on the forum. http://forum.allaboutcircuits.com/showthread.php?t=16232 It works .
    I would like to add a capacitor to compensate for high demand of current. A motor for example could cause a sudden reduction of voltage that would cause the circuit to shutt off.

    Where should I put the positive of the capacitor for discharge? The two X shows 2 trials that failed.

    JP
     
  2. #12

    Expert

    Nov 30, 2010
    16,278
    6,789
    Remove the diode from the 20400 capacitor. Replace it with a wire. It is blocking the capacitor from providing any help. Another capacitor might be added to the points marked V+ and V- if the load is subject to sudden changes.
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,002
    3,229
    Why does there appear a diode in series with the large capacitor? That would prevent the capacitor from working.

    Try connecting a capacitor across the zener diode.

    Post your .asc file.
     
  4. j4e8a16n

    Thread Starter Member

    May 1, 2013
    33
    0
    Here is the new shematic. I used a relay because on small load (led) it was not closing.

    " Another capacitor might be added to the points marked V+ and V- "
    In place of C1?

    JP
     
  5. j4e8a16n

    Thread Starter Member

    May 1, 2013
    33
    0
    The 1K resistor would prevent the current from flowing to the load ... No?
     
  6. crutschow

    Expert

    Mar 14, 2008
    13,002
    3,229
    What has that got to do with my post? :confused:
     
  7. #12

    Expert

    Nov 30, 2010
    16,278
    6,789
    "Added" and, "in place of" are mutually exclusive.
    It just means, "added".
    10 nf is not a big capacitor but it helps at high frequencies where an aluminum electrolytic doesn't work very well.
    Still, I see crutschow is not plainly saying he agrees with me about this capacitor.

    The worst part is that I have to go to a job. Please try to work with crutschow today.
     
  8. ifixit

    Distinguished Member

    Nov 20, 2008
    638
    108
    I made a few assumptions and a few corrections, which should improve how the circuit works. Change C1 to get a different motor start load tolerance.

    Amusez-vous avec elle (Have Fun with it),
    Ifixit
     
    j4e8a16n likes this.
  9. j4e8a16n

    Thread Starter Member

    May 1, 2013
    33
    0
    I dont know what you mean by 'across' the zener.
     
  10. j4e8a16n

    Thread Starter Member

    May 1, 2013
    33
    0
    I will. But I have to be operated for a cataract this afternoon. A simple thing everybody says.

    I did not know you could figure a battery as a pulsed source of current.
    Can you consider a DC P Supply as a pulsed source of current because there is always a bit of DC in it?
     
  11. crutschow

    Expert

    Mar 14, 2008
    13,002
    3,229
    The definition of "across" means "from one side to the other of (something)" which in this case is the zener, or in electrical terms "in parallel with".
     
  12. j4e8a16n

    Thread Starter Member

    May 1, 2013
    33
    0
    I builded it and it works . :eek:)

    It shutted off at 12.1 volts with a led drawing only 30mA.

    I putted a switch to cut the capacitor off when not in use but connected to the battery.

    After 12H, the battery voltage went from 12.8 V to 12.9 V!
     
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