This microwave motion sensor will see the movement of a person at a distance of more than 10 meters and notify about it by blinking the LED. The principle of operation is based on the Doppler effect. A transceiver is assembled on the BFR93a transistor. A signal amplifier and comparator are on the LM386 chip.The transceiver emits a high-frequency signal. When a person moves, this signal from a person enters the antenna and there will be a signal change at the output of the transceiver. This signal is amplified and fed to the comparator.
The antenna is made of copper foil. Make the antenna as shown in the photo.Antenna 1 is located at a distance of 1.5 mm from antenna 2 on all sides.The width of the strips of the two antennas is 5mm
The BFR92a transistor is located in the corner of antenna 1, the base is connected to the corner of antenna 1, and the collector is connected to antenna 2.
On the body of the BFR93 transistor there is an inscription “R2s”
Let’s see how the transceiver works on the oscilloscope. The input of the oscilloscope is connected to the capacitor C3. When there is no movement, there is no change in the signal at the output of the transceiver.
When there is movement, the output signal changes.Now it remains to amplify this signal change and apply to the input of the comparator
The sensor senses finger movement at a distance of up to 1 meter from the antenna. Human movement more than 10 meters away
