1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Square Wave Based Inverter (Switch Mode)

Discussion in 'Alternative Energy' started by C47, Apr 21, 2008.

  1. C47

    C47 New Member

    Joined:
    Apr 14, 2008
    Messages:
    18
    Likes:
    0
    well the 555 timer had 15VDC input....i just thought of checking the "BJT inverter" that you drew....i think all values were ~1.4kohm

    i just made the 555 timer and then the BJT inverter, when the 555 popped.
     
  2. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

    Joined:
    Jan 4, 2007
    Messages:
    21,189
    Likes:
    644
    Location:
    Ex Yorks' Hants UK
    hi,
    Are you saying that connecting as the attached circuit, popped an 555.?

    If yes, you must be doing something wrong...Have you checked the 14V with a meter.?
     
    Last edited: Jul 7, 2008
  3. C47

    C47 New Member

    Joined:
    Apr 14, 2008
    Messages:
    18
    Likes:
    0
    yup that was it....hold on plz i got a professor working now with us....if it gets fixed, I will then post it here
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. C47

    C47 New Member

    Joined:
    Apr 14, 2008
    Messages:
    18
    Likes:
    0

    sorry mate, must have made a mistake somewhere....i managed to invert the signal from the 555 using the inverting buffer (bjt)...also the two signals are 176 degrees out of phase instead of 180, which means that during the run (at a certain point and time) all four switches are open.... :(
     
  6. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

    Joined:
    Jan 4, 2007
    Messages:
    21,189
    Likes:
    644
    Location:
    Ex Yorks' Hants UK
    hi,
    Pleased to hear you are making progress.:)
    Its the transistor invertor thats causing that 176deg problem, a comparator, used an invertor could could be set to give a switch over near 0Volts, in order to give 180deg.
     
  7. C47

    C47 New Member

    Joined:
    Apr 14, 2008
    Messages:
    18
    Likes:
    0
    ok we made this really big circuit....with three 555 timers - one of them providing the clock for the other two

    with the other two we can vary the duty cycle and make it work.....this is still in progress as one timer give 70% (as we want) and the other is giving 1% (we want 20-25%) - i tried changing the values of the resistors and capacitors .... anyway this problem is being worked on....

    your idea of having two pnps...i have tried it in pspice... i will post it soon
     
    Last edited: Apr 28, 2008
  8. C47

    C47 New Member

    Joined:
    Apr 14, 2008
    Messages:
    18
    Likes:
    0
    here is the ckt

    it works in pspice...had a bitof difficulty finding proper pairs.....then had to adjust the R values for the base for each transistor

    thanks a lot ericgibbs
     

    Attached Files:

  9. mneary

    mneary New Member

    Joined:
    Feb 27, 2007
    Messages:
    4,502
    Likes:
    67
    Location:
    California USA
    Your PNPs are upside down. You should swap emitter and collector on both of them.
     
  10. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

    Joined:
    Jan 4, 2007
    Messages:
    21,189
    Likes:
    644
    Location:
    Ex Yorks' Hants UK
    hi,
    I agree, I would have thought his simulation program would have burped and thrown up a warning... the 'base' voltages, wrt 0V, on the reversed transistors should have been an indication.

    Check it out C47..:)
     
  11. C47

    C47 New Member

    Joined:
    Apr 14, 2008
    Messages:
    18
    Likes:
    0
    it doesnt seem to make a difference...i am building the ckt now...will keep that in mind
     

    Attached Files:

  12. C47

    C47 New Member

    Joined:
    Apr 14, 2008
    Messages:
    18
    Likes:
    0
    arrgghhh!!!

    the legs work separately but when i put the whole thing it doesnt work....i think that the timer cannot drive all four...
     
  13. mvs sarma

    mvs sarma Well-Known Member

    Joined:
    Oct 29, 2006
    Messages:
    3,512
    Likes:
    76
    Location:
    Hyderabad, India.
    legs drive 2 transistors only at any time
    now worry. please take care of base current needs by managing the series base resistor.
    555 has adequate capacity.
     
    Last edited: Apr 29, 2008
  14. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

    Joined:
    Jan 4, 2007
    Messages:
    21,189
    Likes:
    644
    Location:
    Ex Yorks' Hants UK
    hi,
    The circuit you have built, NOT simulated, does it have the 10K resistor as the load or the motor and is it the last circuit you posted.?

    If its a motor, whats it voltage and current rating.? The 20K/10K base resistor look too higher a value.

    The 555 should be able to drive that bridge with no problem.
     
  15. mneary

    mneary New Member

    Joined:
    Feb 27, 2007
    Messages:
    4,502
    Likes:
    67
    Location:
    California USA
    At extremely low currents, emitter and collector of many BJTs are almost interchangeable. This is one of the traps of simulation.

    Lesson: Simulate with your intended load!
     
  16. C47

    C47 New Member

    Joined:
    Apr 14, 2008
    Messages:
    18
    Likes:
    0
    well its done....a 555 timer with an inverting buffer driving four NPN H-Bridge...it didnt work the first time coz of the base resistances...and also becoz the inverting buffer had popped (the second time)...so my 12VDC power supply showed a short circuit

    it works.... finally

    thankyou very much everybody
     
  17. shaifymehtadnn

    shaifymehtadnn New Member

    Joined:
    May 6, 2010
    Messages:
    2
    Likes:
    0
    i want the analysis setting of this circuit or attach project files.....
     
  18. shaifymehtadnn

    shaifymehtadnn New Member

    Joined:
    May 6, 2010
    Messages:
    2
    Likes:
    0
    plz attached the project files of the pspice....
     

Share This Page