Led Flashing Speedup

Discussion in 'The Projects Forum' started by IamNew, Dec 13, 2011.

  1. IamNew

    Thread Starter New Member

    Dec 7, 2011
    Hi there, I had a LED flashing circuit here and the LED blinking quite slow for me and I am thinking to make it blink a little bit faster.

    Here is the circuit:


    Please guide me. Thanks in advance.
  2. Wendy


    Mar 24, 2008
    You can make the capacitor larger, double it value and half the flash rate.

    Same thing for R2
  3. t06afre

    AAC Fanatic!

    May 11, 2009
    If you want to have a go on the problem by your self. Take a look at the data sheet here http://www.national.com/ds/LM/LM555.pdf and read the ASTABLE OPERATION section. Then note the formuales on page 8. If you struggle please just ask for more help.
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
    As t06afre posted, you can use the datasheet to find the formulas for calculating the duty cycle and flash rates. It's actually not too hard, but in the meanwhile, here is a table that shows some options. The top row shows what you have now, which should produce a flash rate of .07 Hz (on and off once in about 14.3 seconds.)

    You can speed it up by decreasing C1; as shown in the table, changing C1 from 100 μF to 10 μF increases the flash rate to .72 Hz, (on and off once in about 1.43 seconds.)

    Another way to increase the flash rate is to lower R2; see the table for some examples. In fact, you can play around with the values of R1, R2, and C1 to see the results in duty cycle and flash rate. R1 can't go a lot lower than 1000 Ω, or it begins to get too hot.