Real working bat detector!
My bat detectors will let you listen to bat activity around you. They can hear bats to a distance up to about 100 feet away. They will easily sense bats around you. We use them often at home and while camping or on the water kayaking. I have been making and using bat detectors for more than 6 years. This is one of my more artistic versions, packaged in a black glass box using stained glass techniques. The box contains exposed lead solder on the seams.
Bats use a remarkable high frequency system called echolocation to hunt for insects and guide their path in the dark. Echolocation works in a similar way to sonar. Bats make calls as they fly and listen to the returning echoes. A bat can tell how far away something is by how long it takes the sound to return to them. These calls are usually at a frequency too high for humans to hear naturally. This detector digitally divides that high frequency so that humans can hear it. Just set it on a table outside at dusk and listen. In the early evening, you can often see the bats that are detected.
Using the bat detector is easy.
There is one power switch, a volume control and a sensitivity control. Turn the detector on, adjust the volume and sensitivity controls, set on a flat surface where you expect bats. Holding in your hand is OK, but you must keep a firm grip on the detector to avoid making noise. Try it, you will understand. Also, the box is made of glass, it may break if dropped! Again, the solder seams on the box contain leaded solder. Audio from this bat detector is not very loud! It is plenty for a few people together who may be talking together but maybe not so good for a large party. You may notice that your detector can hear sounds other than bats. There are insects that will become audible with the detector, as well as man made sounds. Hamburgers on the grill will drive it crazy! You can test the bat detector by lightly rubbing your fingers together near the microphone.
This bat detector is built in a black glass box. It is intended to be set on a table but you can also hold in your hand, just do not drop!
There is a standard 9 volt battery inside. Battery should last at least 12 hours, up to about 30 hours. Any kind of "9 volt" rechargable battery should work fine.
How does a bat detector work?
This bat detector works by picking up the ultrasonic sounds made by bats (also other creatures and things) via a microphone, the sound then goes through two stages of amplification with a little high pass filtering. The signal then goes to the CD4024 chip which divides the audio by 16 resulting in a sound that can be heard by humans. That signal then goes through a filter to make it sound a bit better and remove some of the high frequency sound to avoid feedback. After that a volume control, then a standard amplifier drives the speaker.