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Using 16f628 to make quasi-3-phase 400 Hz

Discussion in 'Electronic Design' started by jtaylor, Jan 14, 2005.

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  1. jtaylor

    jtaylor Guest

    I need to make three-phase power at 400Hz to run a pair of selsyn fuel-tank
    units. It lookes like the simplest approach would be to program a pic and
    run some audio power transistors from the outputs. I'd appreciate any
  2. Yes, that depends on the required power level. For 10W that might be
    doable. Above somewhere comes the level where a switcher is better,
    meaning the increased complexity pays power wise.
    You'll need a control loop whenthe load is not just a resistor, but
    something dynamic, a nonlinear 4 quadrant load.

  3. Rich Grise

    Rich Grise Guest

    You don't need three-phase if what you have is actually selsyn motors. The
    three "phases" are really just angle signals, from the one to the other.
    The armatures just get single-phase. You still need to make it, but it's
    easier to make a one-phase oscillator than three. :) And yes, you can
    make a sine wave with a PIC, but you don't need it. Any old oscillator and
    power amp will do, as long as you have enough power, but they certainly
    shouldn't take a whole lot.

    Good Luck!
  4. I think a phase shift oscillator is simpler, if you don't need a PWM
    drive for the output. 3 opamps connected in a ring with a resistor
    and capacitor as feedback. I think I have a schematic somewhere.
  5. CBarn24050

    CBarn24050 Guest

    Subject: Re: Using 16f628 to make quasi-3-phase 400 Hz
    You might want to look at the Hitachi 3048 chip. It has a 3 phase pwm
    generator, you can get an evaluation/starter kit for a few hundred.
  6. Bob Eldred

    Bob Eldred Guest

    If you are proficient in code writing, the PIC is a good solution whether
    you need single phase or three phase. I wouldn't use a linear amplifier
    though, I'd have the PIC drive FET switches directly in a PWM mode. Overall
    that would use the least number of parts and be much more stable in both
    frequency and amplitude than any analog oscillator-amplifier scheme.
    Furthermore, it would not dissipate much power and would be applicable for
    any power level from several watts to many kilowatts depending of the FETs
    and their drive. It would be very good for low power, battery operation as
    well if that is a requirement. On the other hand, if you don't know anything
    about code writing in assembly or C, etc. Then your in for some headaches
    and a simple oscillator-amplifier might be a better choice.
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