UHF Doppler Motion Detector

The UHF motion detector below operates on the Doppler radar principle. A radial signal is created by the oscillator (Q1). Some of this energy is reflected back to the generator by an object in the radiated field. The reflected signal will have a different frequency because of Doppler shift if the object is moving. Q1 is an oscillator coupled to […]

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Infrared (IR) Proximity Detector

This is infrared (IR) proximity detector circuit. A matched infrared emitter and detector pair is used in this circuit. The voltage controlled oscillator section of the LM567 tone detector IC is used to set the emitter LED pulses at frequency. In this circuit, the center frequency of the VCO is set to about 909 Hz by combination of capacitor C1 […]

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Ultrasonic Proximity Detector

This is ultrasonic proximity detector circuit. This circuit consist of micropower opamp and a pair of matched piezo-ceramic tranducers. It uses a 9V battery as power supply. This circuit uses the radar principle, when the objects or people is nearby it will reflect the transmitter’s steady tone back to the reciever. Here is the circuit : First circuit is a […]

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