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Check out our new#MakeRadarenvironment! It contains best radar tutorials for beginners, demos that run directly in the browser, and a very hands-on tutorial that brings you from zero to prototyping within just a few hours.
What is radar?Radar (RAdioDetecting AndRanging) - Sensors are sensors which use electromagnetic radio waves to determine presence, distance, postion or speed of objects. As with other waves, electromagnetic (EM) waves exhibit reflection, refraction, diffraction, and polarization. In a radar system, the EM waves are transmitted from the transmit (TX) antenna then propagate in space until hitting a target. The transmitted EM waves then got reflected and head back to be received by the receive (RX) antenna.
Doppler effect:Most of us have experienced the doppler effect in one way or another, the most common is the sudden change in the pitch when an ambulance crosses you.
The doppler effect happens when the distance between the peaks of the waves get closer to each other (frequency shifts up), this happens if the source of the waves is traveling in the direction of the observer, or if the peaks move further apart (frequency shifts down) if the source is traveling away.
This frequency shift 'f' for EM waves can be directly derived from the original wave frequency f0 and the velocity v of the wave source relative to the observer.
And that is how a motion can be sensed by a radar sensor.
If you want to get deeper insights on how radar works, visit our #MakeRadarSchool!
Plug and Play experienceThe #MakeRadar Plug and Play section allows you to easily get started with radar and your radar device.Whether you use it as an 'Out of the Box'-Example or want to learn radar theory with interactive and practical examples - you only have to connect your #MakeRadar device to your PC and watch the magic!
Let's have a look on the given examples:
Raw Data consoleThe fist example is used to see if the boad is working as supposed.You can see the raw data streaming in as UART.
Radar is the perfect motion sensor, when moving your hand or objects in front of the sensor. You or your object are reflecting and distorting EM waves sent out by the radar. Those distorted waves are picked up by the sensor and converted to so called IQ outputs. The visualizer displays the acquired I(t) and Q(t) signals over time as an quantized analog signal from the radar sensor.
To learn more about IQ signals, visit our #MakeRadarSchool.
If you look at the IQ-data shown in the Raw Data Visualizer, you will see that there are two sinusoidal signals that are offset in phase. If you move your hand towards and away from the radar sensor, you will notice that the I(t) signal depening on the direction leads or trails the Q(t) signal in pahse by 90°. Consequently, the direction of motion respectively to the radar can be detected by determining the leading signal.
By using this phenomenon, doors could be opened or closed depending on approach or departure or lights turned on and off.
One benefical property of radar is the capability to measure speed. The measurement relies on a detectable frequency shift bewteen the transmitted and received EM waves - the so called doppler effect. Depending on the deviation to the reflected frequency, a velocity can be derived and diplayed in our speedometer.You can see the frequency shift also in our next example 'FFT Spectrum Visualizer'.
As you can see in the 'Speedometer' example, we use doppler frequencies to measure the speed of a moving object. Since the analysis of those frequencies could be very exhausting within our I/Q-time signal, we are taking advantage of an another analytical analysis method - we transform our time variant signal ('time domain') into the 'frequency domain'. This can be done by a so called Discrete or Fast Fourier Transformation (DFT/FFT).
The frequency domain allows us to see the sinusoidal frequency components within a sampled time signal. So the FFT visualizer shows the same signal as the Raw data visualizer does - only in the frequency domain.
To learn more about DFT/FFT, visit our #MakeRadarSchool.
Using the high sensivity of radar in motion detection we now demonstrate how you can use radar for presence detection. Here the radar uses two different thresholds for evaluation of macro (walking) and micro (breathing, yes breathing!) motion. The macro motion threshold is used to turn the sensor on, then the micro motion threshold (should be smaller then the macro threshhold) is activated to make sure the sensor stays on as long as you stay in front of the sensor.
Time to get your hands on!
Our Sense2GoL board is supported by #MakeRadar.You can either buy a preflashed Sense2GoL Make board or use a standard Sense2GoL board and flash the code below via the Arduino IDE.
Get started NOW!
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