Help required in developing Pulse Generator

Discussion in 'The Projects Forum' started by gargrahul277, Apr 5, 2016.

  1. gargrahul277

    Thread Starter New Member

    Apr 5, 2016
    Hi all : )

    I'm trying to build a circuit that will generate a pulse and need ur guidance in it

    Refer the attached file for details of pulse.

    Period of Pulse = 400 msec
    Duty Cycle = 50%
    With Two distinct voltage levels of 6 and 8 V.

    first im trying to design the circuit on paper and need ur guidance in it to make sure im on right track

    i plan to use 555 timer ic in astable mode and generate a pulse of 8V, period=400 msec with 50% duty cycle
    but the low voltage level in this case is going to be 0 V. and not 6 V which is required.
    so after timer ic i plan to connect a clipping circuit using diode which will clip the low voltage level to 6 V.

    will this circuit work ??
    is there any better idea(circuit) to generate the required pulse
  2. Lestraveled

    Well-Known Member

    May 19, 2014
    It looks like a reasonable design. How exact do you need the output voltages to be?

    Oh Yea, Welcome to the forum.
  3. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    Depends on what this circuit is driving. Clipping the 555 output means using a current limiting resistor, which increases the overall circuit output impedance.

  4. dl324

    AAC Fanatic!

    Mar 30, 2015
    Welcome to AAC!

    I'd suggest making your astable time period 200mS and use a flip flop to guarantee a 50% duty cycle in the 400mS waveform.

    Depending on how accurate you need your logic levels to be, to get your 6V low, you could diode-OR 6V with the output of the timer (which should then have a supply voltage closer to 9V).
  5. hp1729

    Well-Known Member

    Nov 23, 2015
    Can you run the LM555 at +6V on the low rail instead of ground? Something like this. I haven't tried it yet.
    Last edited: Apr 5, 2016
  6. wayneh


    Sep 9, 2010
    Ditto. That's how I'd do it, assuming the timer output supplies enough current. If it needs an external transistor, it gets trickier but I'd still use diode ORing.