Bat detector #2:  (electronic circuit added 4/05)

Bat detector #3:  (electronic circuit added 4/05)

Bat detector (old):  (electronic design added 11/06)

Bat detector microphone pre-Amplifiers:  The microphone pre-amplifier has the job of amplifying and conditioning the signal coming from the microphone. In case of an electret microphone, the amplifier must have a gain that increases with frequency to compensate for the low sensitivity of the microphone for high frequencies. Also the low frequency part must be filtered out. In case of a piezo transducer, the gain can probably be 'flat'. The pre-amplifier can either be realised either using single transistors or with opamps...(circuit added 6/07)

Bug Detector:  (schematic / circuit added 11/06)

Construct a Solar-Powered Varmint Zapper:  Nuts & Volts Magazine Construction Project October 1996 (added 06/06)

Deer Repellent #1:  seismic sensor (added 7/03)

Insect Repellant:  (electronic design added 11/06)

Insect Repellant:  (electronic (schematic / circuit added 4/02)

Mosquito Repellant:  very simple and easy to assemble mosquito repellant using two transistors and handy components. . (added 9/04)

Pest Repeller - Cheap:  (project / circuit added 11/06)

Pest Repeller - Decent:  (circuit added 11/06)

Pest Repeller - Expensive:  (circuit added 11/06)

Ultrasonic Pest Repellent:  Rats, mice are repelled by ultrasonic frequency in the range of 30 kHz to 50 kHz (circuit added 11/06)

Ultrasonic Pest Repeller:  It is well know that pests like rats, mice etc are repelled by ultrasonic frequency in the range of 30 kHz to 50 kHz. Human beings can’t hear these high-frequency sounds. Unfortunately, all pests do not react at the same ultrasonic frequency. While some pests get repelled at 35 kHz, some others get repelled at 38 to 40 kHz. Thus to increase the effectiveness, ….  (added 10/05)

Ultrasonic Pest Repeller :  (electronic (schematic / circuit added 2/05)