Doppler microwave motion sensor with your own hands

A simple microwave motion sensor capable of detecting human or object movement at a distance of up to 10 meters or more, depending on the size of the object. Works on the Doppler effect

In this device, it is necessary to make the antenna correctly, the quality of the sensor and its detection range of the object depend on it

I cut the antenna out of copper foil, you can see its dimensions in the photo. I installed the transistor in the corner of the antenna, so there will be maximum sensitivity

The transceiver is assembled on the BFR93a transistor. It emits and receives a microwave signal. When the object starts moving, the wave reflected from it will be slightly higher or lower than the frequency of the signal emitted by the transmitter. This difference in signals is amplified by an amplifier, and the comparator turns on the LED. It always glows, and when the object moves, the glow stops. But you can do the opposite.

Antenna A1 is a copper foil 25 mm long and 5 mm wide. Antenna A2 is also a foil, a closed rectangle around A1 at a distance of 1.5 mm from A1. An SMD transistor is connected to these two antennas.

The antenna should "look" at the protected object. He senses my movement at a distance of 13 meters

Setup. Connect the oscilloscope probe to capacitor C3. Wave your hand near the sensor antenna and you will see that the signal will change due to your movements.

Next, connect the remaining part to the LM358 chip and set the device to maximum range. The setting consists of moving the transistor in the antenna. Where the sensitivity is better, leave the transistor there. Of course, it is better to assemble the device on the board and not by surface mounting as I have.