Hey forum goers, got yet another mmWave guide for you (we promise this is the last one for a while). This time we are using it with the Pi 5 and doing some extra things that only a Pi 5 can do such as creating a game of virtual air-hockey controlled by the sensor. This mmWave sensor is just such a darn cool thing and we wanted to ensure we had a guide for the big 3 platforms, enjoy!
“Using mmWave Radar to Detect and Track Humans | Raspberry Pi Guide”
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You should include a warning that this is a radio transmission device and there are strict rules in Australia and other countries for the use of such devices. The user should familiarise themselves with these rules to ensure they are obeying the law.
Probably this device is fine to use but years of working with radio transmissions makes me ensure I am operating within the law.
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Hi @James46717
Thanks for the heads up there, I’ve added a warning to the product page.
hi guys, just wanted to see if this was a typo…
Download and unzip the file to a convenient location like your desktop. Before we begin, let’s look at how to modify the script if you are not using a Pi 4 or another board. If you are using a Pi 5, you can skip this step.
i think the “not” is the typo. it seems like its supposed to say “do these steps if you ARE using a raspberry pi 4 or another board that isnt a raspberry pi 5.” is that right?
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Hi @Chris306555 and welcome to the forums,
Yeah, I think you might be right there, Chris, good catch. It definitely sells like that ‘not’ should not be there.
I’m sure Jaryd will get that updated tomorrow.
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Hey @Chris306555, thanks for the catch!
Just went through and updated that, very confusing without that fix ahahah.
Cheers
Can this mm wave radar be used for normal obstacle detection (like walls and floor)? Or is it just for human detection?
Hey @Rohith307625,
Unfortunately, these are tuned to detect humans and not things like walls and floors.
Hi all
Tuning has nothing to do with it.
The reason is that this is a Doppler radar and the target has to be moving away or toward the source to be detected.
As the wall is stationary it will be ignored. As will a human if it stands still. It has to be moving.
This is stated in the descriptive text.
heers Bob
Thanks for the info! is there any sensor like this that can be used for detecting walls and obstacles?
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I use the word “tuned” here a little loosely, but they are designed to detect people and can detect them even while stationary.
As far as I’m aware, humans have a certain reflectivity to 24 Ghz (which it looks for), and it is also looking for micro-doppler shifts that arise from the minuscule movements in the human body. I have held my breath and not moved a muscle in front of this thing and haven’t been able to fool it yet.
Some with some more advanced signal processing can measure a human heartbeat from a range (those usually use true mmWave at 60 Ghz though.)
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There are probably a dozen different sensors to achieve what you are looking for here, and the right one will depend on your project. We have a more general guide on measuring distances that has a few sensors that can be used to detect walls and obstacles.
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Hi Jared
In my working life my dealings with radar would have been pretty much entirely with “Pulse Echo” as it was known as. I have had no “hands on” dealings for many years now. But I don’t think the principles have changed. Physics really.
And yes, with the use of ever higher frequencies doppler can (and is) very sensitive to movement. I would be very surprised if you could stand still enough to fool it.
Just reminiscing it would not be that many years ago that the availability and use of frequencies like 24GHz and 60GHz at the hobby level would have been unheard of. Progress. These days these numbers are tossed around as if they have been in use forever. Probably have been in existence for some time in Professional and Lab environment but not available to us mere mortals.
Cheers Bob
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Hi Jaryd
I want to extend the length of the cable from the sensor to the Pi. Is there a recommended maximum length of cable?
Clive
Hey @Clive289721, welcome to the forums!
This one is a bit of a curveball to say the least ahahaha. I have only ever done long-range testing with an I2C OLED screen and these ethernet breakouts (using the ethernet cable as the wire connecting the screen and a Pico). We were able to get about 20 meters with that.
HOWEVER, this radar sensor is pulling a lot more current (200 ma), and it’s using quite a high-speed baud rate - both of these will greatly reduce the maximum range of the connecting cable. It’s hard to say without testing, but I would wager you would struggle to get this to reliably work past 2-3 meters. Again though, this is just a guess and would need some testing to confirm.
Hope this helps!
Hi Jared
I think Clive wants to know how far he can extend the signal/power wires NOT the measurement range.
My thoughts would be “not very far”. As the data is via UART it is “single ended”. That is one data wire and ground. The TX and RX and power share a common ground.
Basically not too unlike RS232 but this system could use +/- 12 or 15V where I think UART would be 5V and ground. I would be happy to be corrected on this as I have very little experience.
But the limiting factor would be the UART system is “unbalanced” and includes the power ground so I reckon that without special wiring techniques and low capacitance cable your max length would be a couple of metres at best. To get more you would need probably RS422 or if duplex RS485 which for a sensor might get a bit messy.
I just agreed with that. But in testing, it would be far more use if you did “proper” testing. Not just it works or it doesn’t style “testing”.
Cheers Bob
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Thanks for the feedback guys. I will try out to a couple of meters and if that fails plan b.
Clive
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