Here’s a cool DIY on how to make a bat detector. I am not sure if I will ever need this but seems like
a good circuit to have a knowledge of. You can of course buy one for like 70 bucks if you need one fast.
Bat’s are fascinating creatures and here in Melbourne they are a common sight. At dusk streams of grey-headed flying foxes leave their camp in the Royal Botanical Gardens to plunder fruit and nectar from suburban flowering gums. The number of urban bats have swelled in recent years, giving the impression that the grey-headed flying fox is thriving, but in reality Australia’s bat population has decreased by 30% over the past decade. The increase in urban bat colonies is the result of ongoing destruction to the bats native feeding grounds. The Melbourne Royal Botanical Gardens is now the only breeding colony of grey-headed flying foxes in the state of Victoria. In 2001 the Royal Botanical Gardens started shooting these animals in an insane attempt to curb the local bat population. Thanks to public outcry and a dedicated group of protesters this practice was stopped. The grey-headed flying fox has since been classified as a vulnerable species by the Australian government.
A bat detector is an instrument that will detect the presence of bats by tuning into the echolocation ultrasounds they produce. There are a variety of commercial bat detectors available but what excited me were the numerous internet sites with home-built detector circuits. I stumbled across these sites while trying to decide what to do with a 1968 Braun Cylindric T2 cigarette lighter. What resulted was the Cylindric Ultrasonic Bat Detector.