Need Delay Timer Relay Circuit On/off

Discussion in 'The Projects Forum' started by asking, Dec 6, 2011.

  1. asking

    Thread Starter New Member

    Dec 6, 2011
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    0
    Hello Friends,

    I have Made an LED Board for my shop. I want to make it on for 3 Seconds. then Switch it off for 1 Sec. In this way cycle should countinue. So please Suggest me NE555 Timer Circuit along with Relay.

    Awaiting your reply.
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,118
    3,042
    You can probably use a MOSFET as a switch to avoid the more costly and lower life relay. But no matter what, you need to specify the current and voltage that your LED load requires.
     
  3. asking

    Thread Starter New Member

    Dec 6, 2011
    15
    0
    it require 2A Current. So please anyone give me some idea about circuit...design...or give me Schematic how to do it..
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,118
    3,042
    You need a 0.25Hz square wave generator with a 75% duty cycle. There are plenty of resources you can find on how to wire a 555 to provide that.

    Send the output of that timer to the "gate" pin of an N-channel MOSFET, with the "source" pin to ground and the "drain" pin to the low voltage side of your LED load. When the voltage on the gate goes high, the MOSFET offers nearly zero resistance in the current path to ground and the LEDs will light. When the gate is low, resistance goes very high and no current flows.

    You need to pick a MOSFET that will be fully "on" at the voltage of your timer output. If that output is less than ~10V, you'd be better off with a logic-level MOSFET, which will be fully turned on at 5V or less. At 10v or above, you can use a "regular" MOSFET. The MOSFET you choose should also be rated to 5A or more to give yourself plenty of margin over your continuous, expected load.
     
  5. asking

    Thread Starter New Member

    Dec 6, 2011
    15
    0
    thanx can you provide me with circuit ? m new bie i donno exactly how to do it..
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Look at this page:
    http://www.csgnetwork.com/ne555timer2calc.html
    In the schematic, use:
    30k Ohms for R1
    14k Ohms for R2
    100uF (microfarads) for C1.

    However, you have not stated what your supply voltage is. We need that to make certain it will be within an acceptable range. This will also determine what kind of output driver we can use, whether it is a Transistor or a MOSFET.
     
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  7. asking

    Thread Starter New Member

    Dec 6, 2011
    15
    0
    my supply is 12V DC
     
  8. asking

    Thread Starter New Member

    Dec 6, 2011
    15
    0
    thanx alot..
     
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