The one in your video uses triangulation but there are IR sensors which rely on brightness levels. I'm sure you know this but I thought I'd mention it in case others aren't aware.

Mai Mariarti Do you want to use the sensor underwater? If so, you need a different type of ultrasound sensor. If you want to use the sensor above water, then there are several options for waterproof ultrasound sensors. I believe the guy with the Swiss accent has shown us some of these waterproof sensors. Maxbotix makes weather resistant ultrasound sensors. Here's one at SparkFun: www.sparkfun.com/products/11724 If you need help finding a waterproof ultrasound transducer, let us know so we can help you look.

Hello Buddy , do you know what makes tof lidar receivers detect reflected light over 100 meters ? I cant imagine a tiny beam of light hits target 100 meters away and return a tiny receiver .

Look at the rangefinder video. It worked over 1500 meters

Polygonal mirrors can be recovered from old laser printers. They make a superb laser scanners.

You are right! I did not read the datasheet correctly!

You are welcome!

Thank you!

You are welcome!

Thank you for your nice words!

1. Life is not always a success. This is part of the concept of this channel: I test and you decide if you need the stuff (and maybe avoid disappointments). For people with the need of far-reaching obstacle avoidance, the Garmin might be the only possibility.2. Thanks for the hint for another source of Lidars. Another viewer also referenced to the Neato. But I do not know these brands here. So I have to stick to what I have for the moment.

You are welcome!

You are welcome!

You are welcome!

The numbering will appear again, for the moment a few videos behind (200 should be numbered now)

So you must be a specialist (looking at the homepage of the company)! So you used this theorem to determine the different frequencies used?

I left Kearfott 32 years ago after dragging them kicking and screaming into the digital signal processing era by using the original TMS320 on my Correlation Velocity Sensor program. Back then, the TMS320 cost about $1,500 which was a ton of money in the early 80s, and all the old analog guys didn't see any need for this new fangled stuff! :-D The current state of the art in CRT (Chinese Remainder Theorem) is detailed in a 2017 paper called "Robustness in Chinese Remainder Theorem" by H. Xiao et. al. Dr. Xiao is a professor at MIT. I would put a link to it here, but apparently copying into the comments isn't allowed. At Kearfott, we used CRT in our navigation equipment wherever we could, for both frequency estimation when we only had a short glimpse at a signal, and also for range estimation based on multiple frequencies. These were both key to our Doppler Navigation Systems since these systems always needed to provide range estimates for both altimetry and obstacle avoidance purposes. The biggest problem back then was as Xiao described in his paper, insufficient SNR would result in phase errors that could lead to the calculating the wrong number of cycles, or what we referred to as gross error, as opposed to a fine error where the integer number of cycles were correct, and the error was limited to the residual. It seems this is much less of a problem now than it used to be, but for whatever reason, it's still not commonly known that there is a reasonable simple algorithm for solving for the number of elapsed cycles based on the phase residual in a multi-frequency system.

Thanks for the hint. I found it. But it will take some time to read and understand it ;-) BTW you can post links in the comments. Many others do it too. Sometimes they end in my spam folder. But if the links are ok I can allow them.

You are welcome!

You are welcome

Because I share it with 100 other families...

Wow, 100 is a lot. I thought it was a smaller community/property.

300 parking lots on two floors. Including a atomic bunker, of course ;-)

Yes I've seen the video about the bunker... impressive. From what I remember, almost every (new build) house has an atomic bunker in Switserland. I don't even have a cellar, which would be nice to keep some wine. That's why I drink my wine rather fast.

Good strategy, I think!

Totally agree with this comment, what an amazing reference

They already returned in older videos.

We will see if we still call them "cars" then. Maybe they are more "taxis". I do not think it would be of big value to replace me as a driver if I still have to own the car. My work of driving is free of charge. I think a big difference will be that I just order "transportation" and it will be cheaper than driving my own car because these vehicles can be operated 24/7 and not only one hour or less a day.

I do agree.

northshorepx is already implemented in volvo

Not in mine. I still have to drive on my own :-(

Owning cars is cheaper than taxis if you need to make a lot of km a day, like if you need to commute long distances. Even with self-driving cars, the taxi company has to pay for the cars, the fuel (electricity since we're in the future) and the maintenance. The taxi company also has to make a profit. So it isn't likely to be cheap.

Thanks for sharing your experience!

Andreas Spiess Hello Andreas . I don’t mean to hound you but I could do with a bit of advice please . As you know in our world at present we have to stay a safe distance of 2 meters apart , but that’s not always ease . I want to build a system with possible distance sensors enclosed in a badge or bracelet . Example when person A approaches person B and if person A breaches the 2 meters the unit activates for a shoe RT time either flashes or sounds or even vibrate . Can you please point me in the right direction on where to get the correct parts and what parts I require . Thank you in advance Seamus Fitzgerald

You are welcome!

@@AndreasSpiess I like your Mexican accent.

You are welcome!

Thank you!

You are welcome!

I am not a specialist. Maybe somebody does it if it is so much better or cheaper.

Those do exist but you need a (military) security clearance to play with them. So I think it's more a matter of patents that stop this tech from being readily available.

:-)

I do not know. Maybe it is in the data sheet?

@@AndreasSpiess thank you for replying...checked data sheet it's mentioned as length/100...have to get one and test however .

The Garmin has a range of Range: 5 cm to 40 meters. Crosstalk is not likely because of the different timing.

You are welcome!

You are welcome!

I got it from dfrobots and I plan to do a video with it.

Perfect :)

Welcome to the channel! The sensors depend on a reflected signal. I assume a quiet oil surface will reflect the beam. However, I do not know on the maximum distance

You have to read the different datasheets and search for what you need.

@@AndreasSpiess, I have seen the datasheets of lidars available in my country. I didn't come across a LIDAR that has 0.5% accuracy at 5m. also the fact that the specified accuracy is not seen reality. From your experience, please suggest me a LIDAR or Ultrasonic rangefinder which as accuracy of 0.5% at 5m

:-)

This is an old video and I am an old man. So I do not remember the details. I am sure you will find answers if you read the specifications. I assume you have to do post-processing to do decisions based on the sensor data. I only tested the sensors.

Bitte, gern geschehen!

:-)

For the moment, I have no such plans. :-(

Thank you!

I assume it is for the light intensity. Distance calibration would need a known distance, I think.

@@AndreasSpiess Thanks :-)

Interesting they use the same principle with radio frequencies

You are right! Thank you.

I do not know. The light has to be reflected back to the Lidar, otherwise, it cannot be detected.

Maybe I will do such a video. At least it is on my list...

It is a similar design as I showed in this video and used in another one. But I did not test it so far.

I have no recommendations for such situations. You have to try which is better.

どういたしまして

:-)

I never did a comparison. Also take into account if it is indoors or outdoors. the VLX... do not work very good outdoors.

If the distances are in the range and the trees not too thin I would give it a try.

@@AndreasSpiess Thank you for your opinion! Might try it then.

I can imagine. But maybe a range finder is sufficient?

I do not know. Maybe you ask your supplier?

No. It seems to be a new product.

You are right, they have quite different properties.

I cannot imagine the accuracy is good enough for a CNC. Lidars use normal lasers.

I think you are right. However, I have no experience with this device

:-)

Your choice. I gave you the basics for decision making.

:-)

No, it was not connected to that. Calibration was done every 100 measurements and these values came randomly.

:-)

I never tried that.

It was pretty much as described in their data sheet

Gotcha. I'll take a look. Thank you..

You are right.

Yes, the darker and the less ambient light there is the better a lidar works, since lidars rely on their own light source (laser) (, and only measures the light of its own laser).

@@juunas500 but dark surfaces will probably absorb the the lights...!

@@lakshmipathibalaji2023 Yes if the material of the surfaces is light absorbing, very dark black matte painted room for example. But if it's just an unlit concrete hall there should be no problem

It is simply a analogRead command an the formula in my chart for the distance. Maybe you even find a library. Like that you can include it in any other Lidar projects

I am looking for 2D or 3D visualizing software for GP2Y0A21YK0F senor or TFmini sensor with only programming arduino.

I never say something like that. Most people used Processing at the PC for visualization and an Arduino for capturing the data. Here is a project of one of my viewers: github.com/Brezensalzer/StepperBotLidar2

Yeah you never say that but i am looking for that. that is why I asked. thank you very much.

Hey if you are looking for affordable LIDAR or a complete ROS compatible Hardware kit for Autonomous Mobile Robot you can check centaurirobotics.in/dev/

Hello, Have you found one since? Thank you.

The calibration of ToF sensor is much more than calibrating distance offset. It have some characteristics change with temperature or ambient light. That’s a bit complicated.

Thank you for sharing your insight. I do not know which sensors still work with the indirect method (signal modulation) and I did not test if I see a modulation on the emitter.

No

You are right. But these algorithms are usually quite deep in the sensor chips. If you want to change that you have to build your own sensor from scratch.

I am sure you are right, but not for cheap (unless you know a way). I need a sensor that can measure a soft target travelling about 5m/s, 0-40m range. I want to calculate speed vs distance, 10% accuracy and 300ms sampling may be enough; but, of course more is better.

My problem back then was the lack of an interface for my IOT devces

I probably could. But this was a one-off test. So it was easier to use an old piece of wood I used already for other distance tests...

Ah of course, K.I.S.S.! Keep It Simple Stupid! :)

I do not know how to do it.

Good idea...

There should be no reflection coming back to the device. The walls are in parallel to the beam

Thanks. Actually that happens to be the case with ultrasonic sensors and IR sensors.

Lasers are very focused. Ultrasonic devices have an opening angle of 30 degrees.

It says "Class 1"

This summer...

I also wanted to point that out: www.aliexpress.com/item/Spare-part-Laser-Distance-Sensor-LDS-for-Xiaomi-Mi-Robot-Vacuum-Cleaner/32879027257.html?spm=2114.search0104.3.29.14ac4de7GzZrMO&ws_ab_test=searchweb0_0,searchweb201602_1_10320_10152_10151_10065_10321_10344_10068_10342_10547_10343_10322_10340_10548_10341_10193_10696_10194_10084_10083_10618_10304_10307_10820_10821_10302_10059_100031_10319_10103_10624_10623_10622_10621_10620,searchweb201603_2,ppcSwitch_7&algo_expid=a166696e-dfee-4394-8201-0a79d6a87c0d-4&algo_pvid=a166696e-dfee-4394-8201-0a79d6a87c0d&transAbTest=ae803_2&priceBeautifyAB=0

Maybe it is very similar to the one I have. Same look and same price.

Good find! I didn't even know that the cheap Chinese robo-vacs had LIDARs already. I was actually going to suggest scavenging used and/or broken Neato or Vorwerk robo-vacs. They (at least the high end models) have featured a LIDAR at least for five years, and from what I have read, it is very good and well documented by the hacker community.

It uses triangulation and there's a lot of community work available for it. I've got a vague recollection of seeing them on ebay for less from time to time.

You are right! I did not read the datasheet correctly!

I'm using this sensor in a lab with my students...

I am a UKpostsr and provide my knowledge in my videos. The rest is on you :-(

@@AndreasSpiess thanks for your reply :)

I think for obstacle avoidance the precision is ok. And its range is very long compared to the rest.

My guess is that it has the best IR detector, and thats why it sometimes still see's sunlight in the above test setup, causing it to get confused and sometimes just output a wrong range all together. Like Andreas said though, they are pretty far off numbers, so it shouldn't be to hard to filter those out/work with averages of several measurements. Edit: Another thought i just had, as its apparently auto-configuring itself at set intervals, maybe thats the cause, the way off returned results are from the moment when the sensor goes into 'setup mode' for a few milliseconds? that would be an easy fix (if interval is met then auto configure but dont return results, else return results)

I have no idea if they would work and how far the LED would reach in water.

I tried to put Garmin Lidar in the tank and get the measurements underwater, but it seems, that glass and water makes strong reflection surface. As far, as I looked through the internet, green lasers are being used underwater, because they have different wavelength. Lidar lite was NIR laser, however, underwater lidars are close to the green spectrum.

Me too...

I do not think so.

Hey, Rajesh if your are interested to to make your own Autonomous mobile Robot you can check bit.ly/CK_9

Usually, you find the links in the video description

If you find the interface description they could be useful

@@AndreasSpiess I think I try to get one for a certain price limit I set my self. Just to look inside, and if the lidar sensor can not be used at least there are other parts to salvage, like motors, wheels, etc..

I made a video with this chip. Maybe you watch it

I just saw you have the newer version. So I have no experience.

I will hack around a little more and find out if I can make it work. I will switch to a "regular" atrduino" with a level shifter. I will keep you posted.

My batteries are usually swollen. You are right.

Where do you got the info from?

Andreas Spiess The RPLidar is based on the Lider from the Neato robotic vacuum. If you disassemble the lidar you find a ccd array sensor. I have not done that because it destroys the calebration of my sensor. But there are fotos and documentation online. hackaday.com/2011/09/12/digging-deep-into-the-neatos-lidar-module/ As sensor it uses the DLIS-2K CCD dynamax-imaging.com/products/line-scan-product/dlis2k-2/

Thank you for the link. Unfortunately the video and the link to the blog are removed. Do you know why?

Andreas Spiess No I don't know that. But you can find patents on the system. patents.google.com/?assignee=Neato+Robotics%2c+Inc.

Fast here is a few 100 full measurements per second.

And I am also not sure about the max distance it needs. Maybe they can stop at a relatively short distance and therefore do not need many different wavelengths?

Seems more like a limitation of your product than the methodology, there shouldn't be any problem to reach 100 measurements per second with phase based metering.

They do have to work at the full range of minimum focusing distance to "infinity" and modern cameras can do dozens of frames per second with full subject tracking using many sensor fields, so clever processing is required within that timeframe as well. The only thing I'm not sure about is whether they can trust that they found the correct distance or they do a verification measurement that the lens focused at the right spot or even do it incrementally... Anyway. Sounds like an interesting research project.

I thought about our discussion and asked myself if they really measure distance or if they search for some patterns inside the picture. I assume their goal is not to know the distance to the mm but to create sharp pictures. So they might use a completely different principle than the one I described. But I have no idea about that matter...

I do not know this sensor. So you have to google to find information (if it exists).

what is mmWave?

Andreas Spiess milli meter wave, frequency above micro wave, Ti and Nxp have IC chips as radar soc, which are not so costly, but u cannot get accurate measurement

Do you have the names of the chips?

Andreas Spiess pls check this, simalar to this NXP and AD also has www.ti.com/sensors/mmwave/overview.html

I do not know

hey, you can now buy Lidar at affordable rates in India, check out centaurirobotics.in/dev/

??

s this a theoretical idea or do you know that my device worked like that? I did not do exact measurements.

@@AndreasSpiess I certainly can't tell you I know as a fact how every phase shift range finder works. I found a Russian guy who had done a write up and claimed this was how it was done (I made up the exact frequencies, but I think he was putting them in the 150-200MHz range). As for whether it can be done theoretically versus practically. I'm pretty sure its quite practical. It'd be like saying you could use an XOR phase detector to do a phase error -> voltage converter, or use an FFT and look at the phase difference by taking the atan (imaginary/real) at the desired frequency. In fact, the Russian recommended using the Goertzel algorithm. It would be possible to modulate with MULTIPLE frequencies simultaneously since you're unlikely to see any optical mixing if you are using FFT or Goertzel which would make it faster. Of course, it also means you have a reduced SNR so you'd have to put out more power to compensate. What I can tell you is, that the method I described seems to be a significantly better option than using a high and low frequency, since a 10MHz wave still gives you a maximum unambiguous range of 15 meters, and these range finders can work out to hundreds of meters.

I looked at the leddarOne. Looks good. I will put it on my list...

:-)