Description
The Dog De-barker, as a finished product, attempts to reduce the frequency of your neighbor's dog barking at night. The mild manner in which it does this is through distraction. By emitting a high frequency chip in response to the dog's bark, it is hoped that this will distract the dog. If this is insufficient, by attaching the device to a higher power amplifier, you can provide a negative stimulus in response to it's barking. The chip frequency is around 25K, and so is not an annoyance to people.
"Users Manual"
To apply the Dog De-Barker, you attach to a spot that is in the general location/direction of the dog, and supply power. Next you align your speakers (a high efficiency, weather proof, piezo array source is in the makings) towards the dog. That's it.
Implementation
The Dog De-Barker was constructed in the finest tradition of post-modernism, that is, it was cobbled together from any thing that worked.   ;-)   The system is composed of fairly independent submodules: Acoustical Signal Gather:   For our audio transducer, we used a Panasonic electret microphone. We found a pre-amp circuit for this and it pieced it together. We also put in a small low pass filter to remove transient acoustical spikes. Digitizer:  We used the Harris ADC0804LCN (as in class) to digitize the output of the acoustical input module. We determined the average DC output and normal level AC variance of the acoustical input module and "configured" the ADC0804LCN accordingly. Microcontroller:  The 8051 is the brains of the outfit. It provides a bit of signal processing. One difficulty that needed to be overcome was determining the amplitude of the input signal from the digitizer information. As we are sampling a fairly complicated locally repeating signal somewhat sporadically, we look for peak values locally on the input, assuming that this is the peak waveform. (A slight smoothing will later be added.) This local max, is then examined for "dog bark characteristics." Currently this is very crude, as most of our time was spend on trying to get the electronics together. The method looks for sounds of sufficient volume that fit in a time window, both maximum and minimum. (A superior method, which we will eventually implement, is to check the sound wave against a stored waveform envelope.) "Diagnostic Readout":  Currently, as the system is still under design, we also have an LED array readout of the intensity of the input as an aid to tuning. Amplifier Activator:  This is a small system that activates the amplifier source current. We are still experimenting with this, and some brave chips have given their lives to the cause.  ;-) If the system is to be plugged in, then we can afford to run a relay (they are very power hunger.) The advantage of this is it isolates the system better (we believe) than a transistor. We suspect that a switching transistor is the most appropriate component to use, but we're too late in the game to use on now, though after the due date this will be investigated. Currently, we are attempting to rig a temp, using a 1×2 decoder input into an op-amp (LM386) and running it into saturation, in an attempt to get a reasonably powerful switch. The decoder is active by the microprocessor. Output Signal Generator:  For our output signal generator, we used a circuit in the Low-Cost Signal Generator book. It uses the Exar XR2206 function-generator IC. We obtained the chip and patched together a high frequency sine-wave generator using Exar's spec sheets. Currently, it is tuned around 10K Hz, though in the final version this should be adjusted to 25K Hz. (This chip can be configured to go up to 100K Hz.) Audio Amplifier:  For our current audio amplifier, we use as the core component the Philips TDA7051 mono amplifier IC. For more serious applications we would go to a more powerful amp. (As the output signal generator had sufficient power to make an audible sound, we at times used just that in the proto.) Sound System:  For the sound system, we have 16 high-efficiency high-frequency piezo electric horns. In the proto, we only use one, but in the final we will construct a 4×4 array source, which locally are non-dissipative.