555 12 - 14V LED Flasher circuit Help?

Discussion in 'General Electronics Chat' started by terke, May 10, 2011.

  1. terke

    Thread Starter New Member

    May 9, 2011
    1
    0
    Hi All;

    I'm new to the group and play with electronics for hobby.

    I would like to know if I can adapt the oscillator #3 circuit to run on 12-14V, using a LM555CN timer, R1=470k, R2=4k7, C1=4.7uF, one 2N2907A, three 2N2222A, and three 3W LEDs?
    My aim is to strobe the LEDs for 15ms every 1.5s
    I think for 15ms I could get away with up to 3A through each strobe, giving a nice bright flash without reducing the life of the LEDs.
    If the above is possible, do I need to put a resistor between the output and the 2N2907A to protect the 555?

    Thank you for your help,
    Mark
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The circuit in post #3 uses a Cmos 555 that works with a supply that is as low as 3V but then its output current is very low so two transistors are used to boost the current to 20mA.

    The 2N2222A transistor has a max allowed current that is too low to drive 3A.
    You could use an ordinary 555 driving Mosfets that will easily drive 3A.

    A high power LED can easily burn out in a duration of 15ms when its current is too high.
    The datasheet probably rates over-current in a few micro-seconds but then you might not see it. Stay within the max continuous current spec.
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    Agreed. If you want me to draw something up I will, but this is a pretty basic circuit. The others were notable for the length of service you would get from the battery and low battery voltage (very small batteries).

    You probably should have started your own thread, hijacking (tacking your request at the end of someone elses thread) is discouraged and considered rude. This is because a thread belongs to the OP (original poster). I suspect a moderator will be along and split it off presently.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    You have hijacked an existing thread:
    555 3V LED Flasher circuit Help?

    I have moved the posts to a thread of your own.
    I also adapted the title, as you are using 12-14 Volts in stead of 3 Volts.

    Bertus
     
    Last edited: May 10, 2011
  5. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,535
    Just so you know, I wasn't busting your chops, if people don't explain things then you never learn.

    The offer to help with schematics was sincere. Let me know your power supply voltage, the quantity and color of the LEDs, and the flash patterns. A 2N2222 is a bit small for high current LEDs, but there are lots of other easy ways to do this.

    LEDs, 555s, Flashers, and Light Chasers
     
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