A/C Powered ICs

Discussion in 'General Electronics Chat' started by tronicsrookie, Sep 2, 2011.

  1. tronicsrookie

    Thread Starter New Member

    Aug 22, 2011

    I am assembling a circuit that will automatically switch on Street Halogen Lamp at night and switch it off during day. I ruled out using LDRs etc for this. Here's block diagram

    [A/C Supply 240/50Hz] > [Xformer] > [Voltage Regulator IC] > [Timer IC] > [Counter] > [Logic IC] > [Triac/Relay] > [Lamp]

    I am tired of repeating these first three stages of voltage step down and regulation whenever I try to assemble A/C power circuits,

    (1) Isn't there a chip in market that combines these first three power supply stages into one, possibly based on rectifier and voltage divider circuit using diodes.
    (2) NE555 won't power through a 3V button cell, would it? Atleast the datasheet said it wouldn't.

  2. SgtWookie


    Jul 17, 2007
    If you rule out LDRs, then you will have to use some form of synchronization with an atomic clock along with tables of sunrise/sunsets over the year and programmed latitude/longitute in a microcontroller, as otherwise your lit vs dark times will be out of sync. Even then, your lighting will not compensate for heavy cloud cover or clear skies.

    There are AC to DC converters that you can purchase pre-assembled, but you may find that their cost exceeds what you might assemble from discrete components. In any event, some form of transformer must be used to step down the voltage to provide galvanic isolation from the mains power.

    The NE555 won't power from a 3v cell, but a CMOS 7555 will. Keep in mind that there will still be a power draw, and the button cell certainly won't last forever.
  3. tom66

    Senior Member

    May 9, 2009
    For a street lamp it is likely to be that a transformer supply will be used to provide safety during maintenance.

    Many cheap consumer products use transformer-less power supplies however these are dangerous and should not be used by novices as they do not provide isolation from mains voltage.
  4. tronicsrookie

    Thread Starter New Member

    Aug 22, 2011
    Thanks for your intrusive and very thorough response. The place where I live, night hours vs day hours only vary by 3 hours during summer/winters. The cloud cover, no matter how heavy, never dims sunlight enough during day so much that a need is felt to switch on street light. The utility company has installed switches on street light poles and asked us residents to use them as we consider suitable :D, I sometimes leave street lights on during day to serve them tit for tat when I get inflated bills.

    Captain Wookie, I want you to do two things, that are required very much in field of electronics.
    (1) Form a company and come up with a chip design that combines rectifier, voltage divider and regulator all in one package, keeping cost < .25 cents per chip. (For getting clean 5VDC from 110/220V/50Hz AC)
    (2) Roll out this product: a toolkit that has stencils/punching tool for cutting out common shapes like DIP sockets, MOSFETs and conductive sheets of any metal found suitable/cheap for easy Circuit board creation. (refer to http://forum.allaboutcircuits.com/showthread.php?t=58483)

    I know you can do it, you sound very intelligent.

    Non Commissioned Officer Jr. TronicsRookie.
  5. debjit625

    Well-Known Member

    Apr 17, 2010
    Please save energy...
  6. #12


    Nov 30, 2010
    Acting like a jerk in front of people with thousands of successful interactions on this forum will not get you where you want to go.
  7. someonesdad

    Senior Member

    Jul 7, 2009
    You can buy light-activated switches for outside lights from any electrical supply business for $10 or so. I put one in for my street lamps about 25 years ago. The only time it fails is when one of our cats sits in front of it, blocking the light and turning on the lights during the day. :p

    Why don't you use wall warts? They're cheap and easily available.
  8. tronicsrookie

    Thread Starter New Member

    Aug 22, 2011
    I didn't say anything wrong, did I?
    You should change your signature from "It's only my opinion, and sometimes I'm wrong" to "It's only my opinion, and most of the time, almost always, I'm wrong".
  9. strantor

    AAC Fanatic!

    Oct 3, 2010
    wow. good luck dude