# How to measure the distance up to 200m (with arduino)???

Hi ... how would you measure the distance up to 200m using the arduino ???
1. What would you use ???
2. Is it possible to modify the PING))) sensor to be able to measure such distance ???
3. Do you think, that this radar kit www.hobbytron.com/r-sg7.html could me modified to do the job ??? There is a 'pdf' file for more information.
4. Or would you use laser - how ???

zholy

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8 years ago
1.) Because you would need EXTREMELY specialised circuitry to pick up the return. The return signal decays with the 4th power of distance. You MIGHT be able to do it, but you'd be faced with beaming the sound source very tightly.

2.) You can't do Time of flight (TOF) measurement with an arduino, even assuming you could extract the return pulse. Total roundtrip time is 1.33 usec, and it can't have the resolution to give anything sensible in that period, and once again, the signal amplification required to handle a signal which is STILL varying by the 4th power of distance is very hard to do.

3.) No, the operating principle is doppler effect, which means ONLY velocity information can be extracted.. The clever way the signal processing can handle the return beat frequency makes them relatively easy to extract the signal from, even after the usual 4th power caveat.

There's this method

....but there are optical reasons why that won't work at 200metres.

There's also the method of "multiple frequency phase shift", that's the way the Bosch and Leica "laser rangefinders" work - its too long and involved to explain here, but you AMPLITUDE modulate the laser source, and pick up the return to beat it against, where you make a measurement of phase difference. You repeat that at many different frequencies. There is a net of equations which need solving then, but essentially that's it. The laser is over modulated at a high frequency and then a phase sensitive detection circuit can extract the signal from well below the noise floor - its like magic !! You'd be amazed how many dB below the floor you can find a signal you expect to.

Sorry, but without a very considerable amount of expenditure in time and materials, what you want to do just isn't possible, sometimes things are like that.
paulware5 years ago
Is it possible to use RSSI from Xbee or XRF module?
I am also interested
clarkgabeul7 years ago
Here is a way :

Search thes info patent is sometime very interresting
They can reach 2.5 picoseconds of accurracy !!! With cheap material like AD9500
mluckham8 years ago
Maybe this would be helpful, indirectly.  Servo Magazine 09-2005 page 63 "Webcam Based Laser Range Finder" used a simple laser pointer attached to the body of a webcam so that the laser dot is in the field of view of the webcam.

With the webcam pointed at a target some calibrated distance away, note the X-Y coordinate of the laser dot.  As the target is moved toward or away from the webcam, the dot moves as well to a different X-Y coordinate.  Some trigonometry tells you the distance the target moved.

At longer distances, the offset between the laser source and the camera body would need to be increased, to improve accuracy.

Now - how to eliminate the need for a webcam???
8 years ago
zholy (author) 8 years ago
I see I made a mistake, when asking this question. I was interesting in measuring the distance by radio, sound or laser.

My simple ideas were :

1. Ultra sonic - if the PING)))) range finder can measure distance to 3m ... why not to make the "PING SIGNAL" stronger, so it can travel 200m ???
2. Laser - i do have two 1W IR diodes and if there would be a way, how to use it for the range finder, I'm willing to use them for this purpose.
3. When it comes to RADIO - when the kit SG7 can measure speed over 300m distance ... isn't it possible to make it measure the distance (not the speed)

If you are able to give me any direction, where and for WHAT should I look, I would be very great full.

P.S. : Answers like throwing arduino will NOT help.
8 years ago
1.) Because you would need EXTREMELY specialised circuitry to pick up the return. The return signal decays with the 4th power of distance. You MIGHT be able to do it, but you'd be faced with beaming the sound source very tightly.

2.) You can't do Time of flight (TOF) measurement with an arduino, even assuming you could extract the return pulse. Total roundtrip time is 1.33 usec, and it can't have the resolution to give anything sensible in that period, and once again, the signal amplification required to handle a signal which is STILL varying by the 4th power of distance is very hard to do.

3.) No, the operating principle is doppler effect, which means ONLY velocity information can be extracted.. The clever way the signal processing can handle the return beat frequency makes them relatively easy to extract the signal from, even after the usual 4th power caveat.

There's this method

....but there are optical reasons why that won't work at 200metres.

There's also the method of "multiple frequency phase shift", that's the way the Bosch and Leica "laser rangefinders" work - its too long and involved to explain here, but you AMPLITUDE modulate the laser source, and pick up the return to beat it against, where you make a measurement of phase difference. You repeat that at many different frequencies. There is a net of equations which need solving then, but essentially that's it. The laser is over modulated at a high frequency and then a phase sensitive detection circuit can extract the signal from well below the noise floor - its like magic !! You'd be amazed how many dB below the floor you can find a signal you expect to.

Sorry, but without a very considerable amount of expenditure in time and materials, what you want to do just isn't possible, sometimes things are like that.

zholy (author)  steveastrouk8 years ago
Thank you very much ... this is, what I would qualify as BEST ANSWER. Thank you very much ... I appreciate it.

Zholy
steveastrouk8 years ago
How hard can you throw an Arduino ? Neglecting air friction, time how long it takes to hit a target.  Its about the only way that'll work, save something like parallax - measure the angles with an input to the microcontroller.

You haven't a hope of building a radar/lidar system for less than 90 quid, and sonar won't work at that range.

Steve
zholy (author)  steveastrouk8 years ago
Yes, I was ... there is the radar kit that is 60 USD (I explain my simple ideas above) ... you can buy laser sensor for laser range finders (on ebay) for 20 USD ... I just need a direction, where tp look for more informations ... the rest / putting things together I'll try on my own. Just tasking, if you have seen something like that, or if you heard about it ...

zholy
8 years ago
You forgot "Tie the Arduino to one end of a long string on a spool. Chuck the Arduino at the thing you want to find the distance to, letting the spool spin freely. Measure the string." :-)
8 years ago

Steve
Re-design8 years ago
Mount a bicycle tire on a handle.  Mount a magnet on the wheel and a reed swithch on the handle.  So that the rotating wheel closes the switch.  Hook the switch to the computer.  Measure the wheel and program the computer to count the rotations of the wheel and calculate and display the distance.  Program in functions such a reset, memory, addition, area etc.

Walk from point A to point B and read the display.
NachoMahma8 years ago
.  A sonic sensor will not have the range you need.
.  I doubt if the radar gun can be easily adapted, but don't know that with any certainty.
.  A laser will require a reflector of some sort. This may or may not present a problem in your application.
.  I'd look at using parallax to measure distance.
zholy (author)  NachoMahma8 years ago
Are you sure about the reflector, when it comes to laser rangefinder. I mean, when you buy rangefinder (cca 90GBP) ... you can point almost at anything - like wall, human, car ... that's what I would like to measure the distance from ... car, wall, building, human ... nothing small.
8 years ago
I have a laser range finder spend \$100.  It has a range of 90 ft.  I've never used it for more than 50 ft so it works for me.

I'm not sure how hard it would be to make one that would go further.
NachoMahma8 years ago
> ... when you buy rangefinder (cca 90GBP) ... you can point almost at anything - like wall, human, car ...
.  Probably not at 200m, unless they have gotten MUCH better in the last few years
frollard8 years ago
As Nacho says - its important to note the application.

What are you measuring?
zholy (author)  frollard8 years ago
The distance form wall, car, human ... human is would be probably the smallest object. I'm looking for a cheaper version - that I can build by my self - to a rengefinder (that costs cca 90GBP). I would prefer and radio or ultrasonic, because the laser one does not work properly in foggy conditions.

Have you ever come to anything like that ???