I am a bit of a novice builder, and have just started using op amps. I building a dog bark deterrent.
I have a microphone, the signal is passed through a 10th order sallen key band pass filter so it is only triggered by 750 - 800Hz ( i signal analysed the bark and it is primarily 780Hz)
This signal is then rectified and charges a capacitor as an integrator which will give a pulse when the dog barks. This is inverted and put into a 555 monostable which then gives a DC output for about 1.5 seconds. All built and tested up to this point - when the dog barks an LED comes on for 1.5 seconds!
I am now in the process of designing a 25kHz sine wave generator (use an op amp as a phase shift ocillator) and a power amplifier to give ultrasound output to a speaker.
My question is .... what is the best way of only switching the oscillator on when I have an output signal from the 555? I want to avoid the power amp being switched on when there is no bark - ie both FETs need to be off so the speaker is not biased either way so as to reduce power consumption.
I have been looking for an OP Amp with an inhibit/enable pin, but cant seem to find one. Also considering a SPST relay triggered by the 555 in between the oscillator and the power amp, but this seems a bit of a bodge!
I have a +/-12V supply with a centre tap. Any suggestions welcome - sketch diagram preferred!
John
I have a microphone, the signal is passed through a 10th order sallen key band pass filter so it is only triggered by 750 - 800Hz ( i signal analysed the bark and it is primarily 780Hz)
This signal is then rectified and charges a capacitor as an integrator which will give a pulse when the dog barks. This is inverted and put into a 555 monostable which then gives a DC output for about 1.5 seconds. All built and tested up to this point - when the dog barks an LED comes on for 1.5 seconds!
I am now in the process of designing a 25kHz sine wave generator (use an op amp as a phase shift ocillator) and a power amplifier to give ultrasound output to a speaker.
My question is .... what is the best way of only switching the oscillator on when I have an output signal from the 555? I want to avoid the power amp being switched on when there is no bark - ie both FETs need to be off so the speaker is not biased either way so as to reduce power consumption.
I have been looking for an OP Amp with an inhibit/enable pin, but cant seem to find one. Also considering a SPST relay triggered by the 555 in between the oscillator and the power amp, but this seems a bit of a bodge!
I have a +/-12V supply with a centre tap. Any suggestions welcome - sketch diagram preferred!
John