To drive 40kHz transducer need help.

Discussion in 'General Electronics Chat' started by oookey, Dec 16, 2014.

  1. oookey

    Thread Starter Member

    May 24, 2010
    Hi all
    I’m working out an ultrasonic bird’s repeller, the power supply is +12V, using 12F615 to generate 40kHz 50% duty pulse, the circuit is attached.
    The values of R3 and R2 are 56Ω, connected in series to the transducer.
    From the oscillator scope,[see attached pdf] 1Volt ripples clearly be seen, despite 0.1uF and 1nF capacitors added, is there any way to reduce it?
    The Vpp is 6 volts, how should I increase the Vpp, though this would power the wave to travel further distance.

  2. Sensacell

    Well-Known Member

    Jun 19, 2012
    Your output bridge is a complimentary follower, it cannot produce an output swing greater than the input signal from your MCU. (0-5 V)

    You could add a level shifter stage after the MCU to create a 0-12 volt swing.

    Additionally, the two resistors that create the 1/2 Vcc node burn lots of power, increase the value of these resistors and parallel them with capacitors to make the AC impedance of this node low, while burning much less power at DC.
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Most any audio amp IC would fit here, even the humble LM386.
  4. oookey

    Thread Starter Member

    May 24, 2010
    Thanks Sensacell and ErnieM for suggestions, any way I tried h-bridge connection on the transducer, and program the PIC MCU to produce 50% pwm, the waveform just wonderful as wanted. Bravo!