Light control

Discussion in 'The Projects Forum' started by bwaley, Jun 1, 2008.

  1. bwaley

    Thread Starter Member

    Jun 1, 2008
    Im designing an automatic Light control capable to sense natural illumination of the room and the other to sense presence of a person in the same room after which action is executed. Help me in choosing the transistor ,resistors, LDR, TRAIC for my circuit.
  2. bwaley

    Thread Starter Member

    Jun 1, 2008
    are there logic gates esp. NAND gates whose input (HIGH or 1) is 12 V?If there give me the code.
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    Please don't hijack threads by posting your topic into them. Always start your own.

    4000 series CMOS logic will operate with Vcc up to 18 volts.
  4. SgtWookie


    Jul 17, 2007
    In the CMOS 4000 series, there is the 4093, which is a quad NAND gate with Schmitt-trigger inputs.
    With Schmitt-trigger inputs:
    1) A logic '0' is 1/3 or less of the supply voltage.
    2) A logic '1' is 2/3 or more of the supply voltage.
    3) In order to change the output from one logic state to the other, you have to cause the input to cross from one threshold to the other (ie: from >=2/3 of the supply voltage to <= 1/3 of the supply voltage or vice versa)

    If you wanted a logic '1' to trigger at 12v without any other "massaging" of the input signal (such as resistive dividers), you would need to use a Vdd of around 18v, or the maximum for many CMOS 4000 series ICs (and exceeding many of their maximum voltage supply ratings)
    Last edited: Jun 1, 2008
  5. bwaley

    Thread Starter Member

    Jun 1, 2008
    Thanks Alot For Your Support.