120 Second Voice Recorder:  (schematic added 11/06)

Clap Activated Remote:  (circuit / schematic design added 11/06)

Clap Relay:  Clap sensitive on-off Relay.  3V Battery operated, small portable unit, (added 03/05)

Clap Switch:  Circuit / schematic (added 02/05)

Deer Repellent #1:  seismic sensor (added 02/05)

Dog Whistle:  It's well known that many animals are particularly sensitive to high-frequency sounds that humans can't hear. Many commercial pest repellers based on this principle are available, most of them operating in the range of 30 to 50 kHz. From what I've 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 won't work simply because dogs can't hear it. Therefore, I decided to construct a new circuit (based on the venerable 555, of course) with variable pitch and a relatively loud 82 dB miniature piezo beeper. The circuit 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.... (added 11/05)

Hand Clap Electronic Control:  turn relay on and off by hand Clap (added 5/02)

Hand Clap Lamp Control :  What a way to drive a triac. This is the improved/redesigned version. (added 2/05)

Perimeter Monitor:  Using a single cable such as speaker wire or doorbell cable, this circuit can be remotely positioned, for example, at the bottom of a garden or garage, and used to detect all sound in that area. The cable can be buried in a hosepipe or duct and is concealed out of sight. The mic is an ordinary dynamic mic insert and should be housed in a waterproof enclosure with the rest of the circuit. (added 4/02)

Sound Activated Toy :  This circuit makes a flower bop to the beat of music. The flower stem contains a crooked wire which is spun by the motor. The circuit is a microphone driven peak-detecting one-shot and works very well. The microphone is in a sponge mount to insulate it from the vibration of the running motor. Similar circuits are used to drive rock'n coke cans  (added 2/05)

Sound Controlled Flip Flop:  Described here is a very inexpensive solution to many phono-controlled applications like remote switching on, for instance, or activating a camera, tape recorder, burglar alarms, toys, etc. The circuit given here employs a condenser microphone as the pick-up. A two-stage amplifier built around a quad op-amp IC LM324 offers a good gain to enable sound pick-up upto four metres. ….  (added 10/05)

Sound Operated Switch:  This sensitive sound operated switch can be used with a dynamic microphone insert as above, or be used with an electret (ECM) microphone. If an ECM is used then R1 (shown dotted) will need to be included. A suitable value would be between 2.2k and 10kohms. The two BC109C transitors form an audio preamp, the gain of which is controlled by the 10k preset.  The output is further amplified by a BC182B transistor. To prevent instability the preamp is decoupled with a 100u capacitor and 1k resistor....  (added 2/06)

Sound Operated Switch #2:  (electronic (schematic / circuit added 4/02)

Sound Triggered Flash:  (project / circuit added 11/06)

Ultrasonic dog whistle:  (electronic design added 11/06)

Ultrasonic Dog Whistle:  (electronic design added 9/02)

Voice Recorder:  (schematic added 11/06)

Wave Multiplier for music Synthesizers:  (electronic circuit added 4/05)

Whistle on Whistle Off:  This CMOS toggle flip flop circuit has an addition of2bandpass filters and condenser microphone so the relay can be toggled by whistling at it. (added 5/02)

Whistle Responder:  Beeps when hears your whistle A gadget suitable for key-holders, games etc. (added 9/04)

Whistle Switch:  (electronic (schematic / circuit added 4/02)