How to construct a PWM circuit using 2 Timer 555

Discussion in 'The Projects Forum' started by cloud623, Dec 16, 2007.

  1. cloud623

    Thread Starter New Member

    Dec 16, 2007
    9
    0
    i try already using many method construct the PWM, but i found that timer 555 and easily control the waveform and build the cicuit. So anyone can teach me use 2 timer 555 build the PWM circuit.
     
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    How about PWM with a single 555? If you use a 5V supply, I would recommend replacing the MOSFET with one specified for 5V logic level gate drive.
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
  4. cloud623

    Thread Starter New Member

    Dec 16, 2007
    9
    0
    thanks a lots u 2 guys. but i mean one 555 is as a Voltage-controlled oscillator, another one is PWM 555. so refer below i attached Voltage-controlled oscillator 555 and other 2 PWM 555. How to combine can be adjust the pulse width by using voltage control.
     
  5. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    If you want variable frequency, and variable duty ccle, and you want them to be independent of each other (duty cycle doesn't change when you change frequency), I don't think you can do it with a couple of 555s. Maybe not even with 100 555s.:D You can do it with some other parts, though.
     
  6. cloud623

    Thread Starter New Member

    Dec 16, 2007
    9
    0
    yes, i just want change the duty cycle not the frequency, so how to change the duty cycle? THX ^ ^
     
  7. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    The first circuit I posted does that with one CMOS 555.
     
  8. cloud623

    Thread Starter New Member

    Dec 16, 2007
    9
    0
    thanks a lots, Mr. Ron H. May i ask one question is the diagram you given that 555 pin 7 and pin 7 are not need to connect or need to connect other circuit?
     
  9. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    Pin 7 is not needed. Leave it disconnected.
     
  10. cloud623

    Thread Starter New Member

    Dec 16, 2007
    9
    0
    then the pin 5 is also disconnect? if i need a 50Hz frequency, which component value i need to change?
     
  11. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    That's what the schematic shows.
    I'm not sure, that's a tough one ... but you might look in the vicinity of the note which reads "CHANGE THIS CAP FOR PWM FREQUENCY" :rolleyes:
    (hint: .047uF)
     
  12. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    Why are you wasting days asking pointless questions? I posted the schematic 10 days ago. You could have built it and tried it out in a few minutes.
    If you are reluctant to order parts until you are sure it will work, then tell us that. As you can see, we're starting to get annoyed (or at least I am).
     
  13. gootee

    Senior Member

    Apr 24, 2007
    447
    50
    And if you don't have the parts, or the test equipment needed, you could at least download the LTspice circuit simulator from http://www.linear.com and test the circuit that way. You can change component values and see whatever waveforms you want, etc etc.
     
Loading...