What is the best way to make an AC chopper and a DC chopper circuit?

Discussion in 'Power Electronics' started by Michael George, Oct 5, 2016.

  1. Michael George

    Thread Starter Member

    Feb 8, 2015
    I'm a student and this is the project of the final year in my collage. I really need your help and advice.

    I need to make an AC chopper circuit and a DC chopper circuit to control high power load such as: light dimmer (100 W bulb) or Controlling the speed of a small motor or simple resistive load... whatever the load.

    I need the circuit to be stable and reliable, Not like the circuits that sometimes work and sometimes not.
    It should work with wide range of loads regardless the temperature and any other factor that can affect the working of the circuit.

    Would you answer these questions, Please?

    1. What is the best IC and transistors to make this project? What is their part number?
    2. Is it better to make it using Arduino and microcontrollers?
    3. Can I make one circuit that is able to work as a DC chopper and AC chopper? Or Should I make two separate circuits, One for DC chopper and another one for AC chopper?

    Thank you very much, I really appreciate your help.
  2. wayneh


    Sep 9, 2010
    I would separate the DC and AC circuits. If someone has a clever solution to merge them, that's fine, but I'd stick to modular functions until you learn more about this.

    There are many choices for a DC circuit. Many people use a PWM circuit based on the 555 timer IC. Or, you use an op-amp to generate a triangle wave and a comparator to choose the duty cycle. And there are dedicated ICs designed for PWM.

    On the AC side, are you talking about making a simple triac light dimmer?

    You don't need a microprocessor for either of these simple circuits unless you need more from them than you've described, for instance if you need a certain dimming profile over time.
    Last edited: Oct 5, 2016
    Michael George likes this.
  3. Michael George

    Thread Starter Member

    Feb 8, 2015
    @wayneh Thank you very much for your reply,

    For DC circuit:
    I don't prefer working with 555 because I think it has inaccurate timing.
    I did not try a triangle wave generator (op amp) nor PWM IC before. So, Would you tell me your opinion which one is better? and would you provide me with a part number, please?

    For AC circuit:
    A simple triac light dimmer may not be accepted as a final year project. I made one of them before and it amazes me. I was really excited about it but my collage may have a different opinion.
    Maybe it would be better if I added an LDR to automatically adjust the light or some means of protection such as overload or short circuit protection. And Is there a way to control the duty cycle by changing the input voltage instead of changing the phase shift of the RC circuit? So that it is easier to predict the duty cycle.
    1 volt of input = 25% duty cycle
    2 volts of input = 50% duty cycle
    Thank you again for your time and help
  4. crutschow


    Mar 14, 2008
    If a 555 is not accurate enough then you may need to go to a crystal controlled timer.
    Is that acceptable?
    Why do you need such high accuracy?
    Michael George likes this.
  5. Michael George

    Thread Starter Member

    Feb 8, 2015
    A crystal controlled timer is great idea. Does that mean I need a programmable microprocessor? or Can I just use an un-programmable IC with crystal oscillator?

    If the circuit is not good enough, I will not be graduated :)

    A vendor told me about this project. He told me that it controls the speed of a motor but he does not know if it is an AC chopper or not.
    Would you look at the circuit in this .pdf file and tell me if it is an AC chopper or not, Please?
    If yes, I will start learning each part of the circuit and I will build this project. Here is the link:
  6. crutschow


    Mar 14, 2008
    So how good is "good enough"?
    That's not an engineering requirement. :rolleyes:

    The circuit appears to be a phase-controlled AC circuit using a TRIAC.
    Michael George likes this.
  7. shortbus

    AAC Fanatic!

    Sep 30, 2009
    The future of electronic/electrical engineering? :eek:
  8. tcmtech

    Distinguished Member

    Nov 4, 2013
    My thoughts exactly.

    Senior year and cant read a simple schematic, doesn't know the terminology and differences between DC and AC power control and figures a 555 timer is not accurate enough for basic PWM/phase angle motor speed regulation. :(
    shortbus likes this.