Uses a 555 timer IC to generate a 720Hz triangle waveform (at pin 2 of the IC). This waveform is of about 50% duty cycle. This triangle waveform is compared to a fixed voltage with a comparator, IC2. The fixed voltage can be varied by potentiometer VR1. [....] Link
Today we come to see the circuit detects the light by have a voice warn. When meet the light or be become dark depend on using S1 ( follow the circuit ). For this my circuit uses the integrated circuit IC 555 be pillar equipment again. You can choose can use many the number be [...]
This is a simple high pitch noise generator circuit. It has a timer oscillator with a frequency variable from 15khz - 30khz.
The circuit can be mounted in a plastic box like I have done. The good thing about high frequency sounds is that it is very hard to find where they are coming from. Also, [...]
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