Radar Sensors from $3 to over $100: Which one is Best?

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Lately, many radar sensors have become available  for relatively cheap prices. In this video,   I will give you an overview of what is  available and how they compare. And, of course,   we will have a look into how they work and test  a few of them. After viewing this video, you   should be able to choose the right sensor for your  needs. And you should know which are overpriced.   Grüezi YouTubers. Here is the guy with the Swiss  accent. With a new episode and fresh ideas around   sensors and microcontrollers. Remember: If you  subscribe, you will always sit in the first row.   Over the years, we got a few iterations of  radar sensors. Some of them were very cheap,   but most of them were quite expensive. This  changed with the arrival of new radar chips   for 24GHz and 60GHz. So, today, we will: - Look what radar sensors can   measure and how they do it - What kind of sensors we get   - How they compare - Do some testing   - Check the integration in Home  Assistant or other applications   - And finally, you get my verdict Radar is the abbreviation of “radio detection and   ranging”. It was very important for the outcome of  World War II, where it got a huge push when cavity   magnetrons were invented by the British who shared  them with the Americans. These high-performance   tubes enabled the building of strong transmitters  for very high frequencies. The high frequencies   were needed because the resolution of a radar  heavily depends on its frequency. And the high   power was needed because they wanted to  detect far away and small airplanes.   Radars emit signals and listen to  the part reflected by conductive   material such as metal or water. Because they use directional antennas,   they can detect from which direction a signal  is reflected and how strong. Early radars just   showed the presence of an object. Later, they  used the Doppler effect to determine its speed.   Fast-moving objects reflect the signal  on a higher or lower frequency, similar   to a passing police car. The bigger the frequency  difference, the faster the object. Unfortunately,   it was not possible to measure distance  exactly until another invention was made:   FMCW radars. They change their frequency at a  rapid pace. This frequency change has the effect   that it not only shows the speed of the plane but  also its distance. Unfortunately, both signals   are mixed. So, the distance of fast-flying planes  is not accurate. Still, the results were usable.   Our new radar modules are based on the same  principles: They transmit on a high frequency,   receive the reflected signal, and make  some calculations. Some radars can only   show the speed, others the distance,  and the more sophisticated, both.   Let’s have a look at the different  generations of such sensors.   The first sensors covered on this channel  were these two: one runs at about 10GHz,   the other at 24GHz. Both were Doppler radars  and provided an audio frequency proportional   to the speed of the detected object. While  the first was hardly working, the second was   able to detect the speed. We tried it for the  detection of bicycles, but we were not able to   get more than a 5-7m range. Fortunately, one of  my viewers, Mathieu from Limpkin, kept trying,   and here we have a small device consisting of a  radar module, a sensitive amplifier, and an STM32   MCU. He did a marvelous documentation if you are  interested in how he built it. In today’s video,   it is one of the few sensors outputting speed. You  get sensors with longer ranges, but unfortunately,   they are still much more expensive. 24GHz is a so-called ISM band that can   be used by everybody without a license  as long as the device complies with the   regulations. 10GHz is no ISM band, BTW. On this module, we see the typical antenna   arrangement: A set of transmitting and a  set of receiving antennas. A rule of thumb:   The bigger the antennas, the more directional  they are. So, the range becomes longer,   and the detection angles get smaller. These modules were quite big and extremely simple.   As Shahriar form “The Signal Path” showed, the  frequency of those sensors is very unstable, and   for sure, they cannot be certified by authorities.  So we need something better. And smaller.   When Smartphones started to include all  kinds of sensors, they were produced in   high quantities for cheap. This is why we got all  our cheap but good sensors like accelerometers. A   similar thing happened with radar. Not with  Smartphones, but with cars. Newer cars need   sensors to measure distance. First came parking  sensors, then the distance sensor with ranges   up to a few hundred meters. They operate at  77GHz. So, companies started to develop cheap   chips for such frequencies. The quality of such  sensors has to be extremely high compared with   our simple CDM324. They need stable frequencies  and sensitive receivers. A similar technology   can be used to produce chips for 24 and 60GHz  radar chips. So also those became cheaper.   Here is a selection of more than 20 boards. The  price range starts below $5 and surpasses $100.   So what do we get for our money? Let’s start with the cheapest:   They are all below $10, and they all come  from the same company, Hi-Link, operate in   the 24GHz ISM band, and contain chips from the  same company. Their output power is quite low,   around 12dBm (16mW). This is not unexpected,  as the cost of power increases with frequency.   The biggest difference is the antennas. Some  have simple antennas with a 60-degree opening.   Others have up to 4 antennas with a reduced  opening of 25 degrees in the vertical and   45 degrees in the horizontal direction. We  should assume that everything else equal,   their range should be much longer. But according  to the datasheet, it is not so. So we have   to test them. The LD2450 has another antenna  configuration. Its range should be in-between.   The model numbers containing 11XX  and below seem to be obsolete.   The only other sub $10 board comes from MicRadar.  Its output power is only 6dBm even if it has   the same chip as the LD2411. Its antenna is  half the size of the larger Hi-Link sensors,   and its datasheet range is 4-8m. The LD2410B and the LD2411S have   Bluetooth. The LD2450, too, but it can  only be used to update its firmware.   So let’s quickly test these sensors. It is  beautiful outside, and Dishka monitors the   tests. The LD2410B gets to a range of around 4  meters, not the 6m of the datasheet. You get an   app for IOS and Android, and you can easily  integrate both of them into Home Assistant.   Either via Bluetooth or connected to an  ESP8266 running ESPhome. The LD2450 only   can be connected to an ESPhome device. The LD2411 and the LD2450 can detect   moving targets up to about 6m. All of  them can also indicate the direction of   the target. This might be a useful feature  if you want to block a particular area.   The next two sensors are $20, respectively $32.  The IFL2411A is similar to the CDM324 as it   outputs an analog Doppler voltage or frequency.  It seems to lack a stable frequency because I   did not find a crystal. For me a special module  without a lot of documentation. This 24GHz module   from Seeeds has similar specs to the LD2450,  just a much higher price. It seems it has been   replaced by one of the newer 60GHz sensors. The  last in the 24GHz crowd is the MR24BSD1. Compared   with all other boards, it has a huge antenna. Its  main purpose is sleeping detection. Its range is   below 3m, which is ok for its purpose. I will  not include it in the current test because of   its special purpose. Maybe I will once make a  video about sleep analyzing radars that would   also contain the next contender: the MR60BHA1. It  operates in the next higher ISM band: 60GHz. Its   price is $45 plus shipping. Its detection range  is only 1.5m, which is okay for its purpose.   What do you miss if you look at this sensor?  Yes, you are right: There are no antennas.   Strange. Only a sharp look at the chip reveals  the secret: The antennas are inside the chip.   The 60GHz wavelength is only 5mm. Incredible! But  of course, the detection resolution of such short   wavelength signals is extremely good. This  is the domain of our most expensive module:   The XM125 from the Swedish company Acconeer. It  works on 60GHz, and has on-the-chip antennas,   too. But its main purpose is the detection of  very small and fast movements over a reasonable   distance. So, its purpose is comparable with the  other contenders. According to its datasheet,   the range is 20m, its update speed is so fast  that it has to be connected via the SPI bus,   and its accuracy is millimeters. The evaluation kit costs around $130. But   astonishingly, the sensor alone is only $25. That  is a very good price if the datasheet is right.   I tried hard to get this sensor to show me its  capabilities. Unfortunately, all the examples of   their tool show a ton of things, but not what I  expected. The only working example was presence   detection at a distance of up to 5m. Nothing  to write home about. I tried walking, I tried   it with my (metal) bike, and I tried to measure  speed. Nothing worked. I felt like a real noob.   Unfortunately, this is not the first time I have  encountered such code. Particularly, technically   savvy people want to show how good they are and  forget that all others are not as good. So guys,   create a noobs mode that just shows presence  for the promised 20m range and speed in the same   range. Then, you can continue with the res t. Just to show you how easy it can be:   Here is the test of Mathieu’s  sensor. It does what is expected.   60GHz is a fascinating technology. I am working  on another video that uses this ISM band. Today,   I can just reveal a detail about why the  60GHz band became a free-to-use ISM band:   The attenuation curve of oxygen has its maximum  right at 60GHz. So signals are attenuated a lot   which is not good for wireless communication  because you lose much of your precious power.   In the next video, we will see if we still get  something usable from this ISM band. Stay tuned.   My verdict? For presence detection, I would go  with the cheap LD2410, and if you need more range,   with the LD2411 or LD2450. Also they can easily  be integrated into Home Assistant. As said,   the breathing detector boards are for a  different purpose and deserve special treatment.   The XM125 has a lot of potential. And for its  price, it could have been a winner if the creator   of this video would have been up to his task. But keep in mind: These are active sensors   and therefore consume around 100mA. So they  have to be powered by mains, not batteries.   This was all for today. As always, you find  all the relevant links in the description.   I hope this video was useful or at  least interesting for you. If true,   please consider supporting the channel to  secure its future existence. Thank you! Bye
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Channel: Andreas Spiess
Views: 131,159
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Length: 14min 30sec (870 seconds)
Published: Sun Oct 15 2023
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