Wiring & diagram Info: whistle

Showing posts with label whistle. Show all posts

Tuesday, September 9, 2014

Whistle Responder

This device beeps intermittently for approx. two seconds when a person in a range of about 10 meters emits a whistle.
The first two inverters contained in IC1 are used as audio amplifiers. IC1A amplifies consistently the signal picked-up by the small electret-microphone and IC1B acts as a band-pass filter, its frequency being centered at about 1.8KHz. The filter is required in order to select a specific frequency, the whistles one, stopping other frequencies that would cause undesired beepers operation. IC1C is wired as a Schmitt trigger, squaring the incoming audio signal. IC1D is a 2 second (approx.) monostable driving the astable formed by IC1E & IC1F. This oscillator generates a 3 to 5Hz square wave feeding Q1 and BZ1, thus providing intermittent beepers operation.

Parts:
R1 22K 1/4W Resistor
R2 10K 1/4W Resistor
R3 4M7 1/4W Resistor
R4,R8 100K 1/4W Resistors
R5 220R 1/4W Resistor
R6 330K 1/4W Resistor
R7 47K 1/4W Resistor
R9 2M2 1/4W Resistor
R10 1M5 1/4W Resistor
C1,C5 47nF 63V Polyester or Ceramic Capacitors
C2,C3 10nF 63V Polyester Capacitors
C4,C6 1µF 63V Electrolytic Capacitors
D1,D2 1N4148 75V 150mA Diodes
IC1 4049 Hex Inverter IC
Q1 BC337 45V 800mA NPN Transistor
MIC1 Miniature electret microphone
BZ1 Piezo sounder (incorporating 3KHz oscillator)
B1 2.8 or 3V Battery (see notes)

Tuesday, August 12, 2014

Ultrasonic Dog Whistle

Its well known that many animals are particularly sensitive to high-frequency sounds that humans cant hear. Many commercial pest repellers based on this principle are available, most of them operating in the range of 30 to 50 kHz. My aim was, however, to design a slightly different and somewhat more powerful audio frequency/ultrasonic sound generator that could be used to train dogs. Just imagine the possibilities - you could make your pet think twice before barking again in the middle of the night or even subdue hostile dogs (and I guess burglars would love that!).

From what Ive read, dogs and other mammals of similar size behave much differently than insects. They tend to respond best to frequencies between 15 and 25 kHz and the older ones are less susceptible to higher tones. This means that an ordinary pest repeller wont work simply because dogs cant hear it. Therefore, I decided to construct a new schema (based on the venerable 555, of course) with a variable pitch and a relatively loud 82 dB miniature piezo beeper.

The schema is very simple and can be easily assembled in half an hour. Most of the components are not really critical, but you should keep in mind that other values will probably change the operating frequency. Potentiometer determines the pitch: higher resistance means lower frequency. Since different dogs react to different frequencies, youll probably have to experiment a bit to get the most out of this tiny schema. The schema is shown below:

Ultrasonic Dog Whistle Circuit diagram

Despite the simplicity of the schema, there is one little thing. The 10nF (.01) capacitor is critical as it, too, determines the frequency. Most ceramic caps are highly unstable and 20% tolerance is not unusual at all. Higher capacitance means lower frequency and vice-versa. For proper alignment and adjustment, an oscilloscope would be necessary. Since I dont have one, I used Winscope. Although its limited to only 22 kHz, thats just enough to see how this schema works.

There is no need to etch a PCB for this project, perf board will do. Test the schema to see how it responds at different frequencies. A 4k7 potentiometer in conjunction with a 10nF (or slightly bigger) capacitor gives some 11 to 22kHz, which should do just fine. Install the schema in a small plastic box and if you want to, you can add a LED pilot light. Power consumption is very small and a 9V battery should last a long time. Possible further experimentation:

Im working on an amplified version of the whistle to get a louder beep. All attempts so far havent been successful as high frequency performance tends to drop dramatically with the 555. Perhaps I could use a frequency doubler schema - I just dont know and Ive run out of ideas. One other slightly more advanced project could be a simple "anti-bark" device with a sound-triggered (clap) switch that sets off the ultrasonic buzzer as soon as your dog starts to bark.