object position detection using ultrasonar

[eda1m]

Re: How to measure distance?

Ultrawave band radio may be the answer

 

[amriths04]

Re: How to measure distance?

i will give you one idea, but i am unsure whether is it practical. just transmit a coherent signal to strike any object whose distance you have to measure. make the receiver a concave surface or a parabolic antenna so that most of the power is reflected back to the point where you transmitted. measure the reflected received power by using some receiver followed by a power detector. you have have information about your transmitted and received power. using antenna theory you can measure the electric power at any point as a function of distance(given in any emf text book). probably you can solve for the unknown, that is, the distance.

dont know whether the above is physically practicable.

 

[si14]

Re: How to measure distance?

for that, you should radar system.
but for measuring in the cable or transmission lines, TDR is the best.

but for your application, you can check remote sensing.
It's very extensive and depends on your work.

keep in touch.
cheers.

 

[smith123]

Re: How to measure distance?

your problem solution is ultrasound

 

[mkiani]

How to measure distance?

yes .youc can use of ultrasonic sensors.just serach "ultrasonic distance meter " or "ultrasonic rnge finder " in google.but maximum distance is about 6 to 10 meters.(with common sensors).

 

[rikie_rizza]

Re: How to measure distance?

The guy said that he cannot use ultrasound!

For 20m, I'll prefer Ir!! Chopper stabilized infra red is easy to use. Just blink the ir source at known frequency, than the reciever has a band pass filter. Measure the filtered signal strength and you'll get the distance... of course after calibration and experimenting you will find the corelation between signal strength and distance. I try this once, and the corelation is linear. So I use Least Square for aproximation with relative error 0.2%.

Good luck!

 

[the_edge]

Re: How to measure distance?

rikie_rizza, I am not sure about this, my source is not nesseseraly pointed directly to the receiver, so as you said that from signall strenght I calculate distance, so I am worried that ir diode will not send signal of same strength in wide angle... In that case I will have longer distance... Am I wright? Or this can be done? It sounds very interesting...

 

[rikie_rizza]

Re: How to measure distance?

One of the device should be controlled by user, either the Rx or theTx. Most ir diode has a lens that spread the beam about 20SR (degree steradian). In order to design an instrument, you must consider limitation and barrier. Dont create something too wide.

If you want to create the ir source spread 360 degree u can use multiple led aming at all direction. To assure uniformity, use 1 R for all LEDs (100ohm). If that is not the answer, use beam spreader that can be created easily using home made cone reflector.

 

[the_edge]

Re: How to measure distance?

This look interesting. You said that you already did it, so can you give me some schematic of transmitter and receiveer? I dont need 360 degree, but as wider it is the better it is... I am not sure how to calculate strength of received signal, what sensor should I use?

 

[raghuram_msc]

Re: How to measure distance?

Hi all,

Let me first appreciate you all for yur hard work all time...!!!!

Guys wat i personally feel is RADAR concept seem quite fitting in this case owing to:-

1. The distance of 30-40m is sufficient for todays DSP to do calcualtions in real-time.
2. If we were to use CW Encoded RADAR signal (with 5-bit full length sequence suitable in this case, if iam not wrong!!) with a seperate antenna for Tx and Rx, may be it can work..!!
3. Talking of the analysis part there is a technique called "back ground cancellation" with respect to RCS (Radar Cross Section) measurements wherein after the measurement (Tx-Rx) the taget is removed and similar run is done without disturbing the environment. This gives us an idea of the "environment-Reflection" which can be cancelled from our measurements...!!

This probably would be help ful but requires quite a lot of analysis...!!!

All the best.
Sai

 

[rikie_rizza]

Re: How to measure distance?

Yeah, RADAR is a good choice, but again it is very difficult to build by hand because the component is overmuch and presision... I dont think that you can make radar just by using a panfry or a wok.

Back to IR. I'm sorry i cant give you any schematic. Anyway, basically it only consist of ir transmitter and a photo cell. Here's a hint:

1. Use photocell because the output is in mV and very sensitive.
2. Or use OPT101 from Texas Instrument, it got a built in instrument amplifier.
3. Use focusing lens (u can get it from a loop) to focus the light. If its hard to do, just use the sensor by itself.
4. Go to www.maxim-ic.com to look for a bandpass filter IC. Order a free sample. refer to the data sheet for usage.
5. Detect the amplitude of the filtered signal. That would be the signal strength.
6. if you can, convert the signal to DC and convert the analog signal to digital.
7. Dont forget to blink the light source.

To be sure of the effect, try it first indoor.
Dont use any signal conditioner component and dont blink the LED.
Make sure the room is dark (dont have to be total). Dont turn on the LED just yet. Connect the photocell output to a voltmeter (digital will be helpful). The A to + and K (the shorter pin) to Com. You will see the actual voltage from the sensor. The voltage indicates the ambient light = Voffset. Now turn on the LED and move back and forth. U'll see the changes... the further u are from the led the closer the the Voltage to Voffset.

After you achieve this, i'm sure you know the rest. Contact me if you still confuse.

 

[the_edge]

Re: How to measure distance?

Is this block diagram that you meean of?

For raghuram_msc, I wish I could build radar, but thanks any way...

 

[hdrzaman]

How to measure distance?

im not getting ur point. Why not lasar?

 

[rikie_rizza]

Re: How to measure distance?

Hey, nice...
Yeah, your good!
Now, have you tested the photocell with the simple experiment that I told you?

Using laser is a good idea. but IR laser is expensive and rare. U can use red laser pointer thou. But, blinking a laser would be much harder than blinking an LED.

 

[the_edge]

Re: How to measure distance?

Why not lasar?

well laser is very directed light source, so you need to point laser directly to sensor so it would sense it...
For the time now I don have time to test it because I need to study for my exams, but I will let you know when I do... Thank you vary much...

 

[tanuki]

Re: How to measure distance?

Laser ranging devices and application notes:
http://www.acam.de/index.php?id=26&L=07

 

[Rexypoo]

Re: How to measure distance?

Triangulation might be the best method of location.
Class 1 Bluetooth can transmit for about 100 meters. I'm not sure how far apart each receiver would have to be, but once placed in an array of known locations the receivers could contribute their data wirelessly toward the calculations.

The simple answer might be to get a cell phone with GPS coordinates and let it triangulate for you off of cell towers.

 

[subharpe]

Re: How to measure distance?

Hi, There was reference of an project in the topic 'signal processing related' where autocorrelation of the transmitted and reflected signals is used to measure the distance of theobject. Youcan see it.

 

[FvM]

Re: How to measure distance?

I just reviewed the discussion and was somewhat surprised, that most posts apparently don't understand the original measuring problem, that had been given very clearly. Without using transmitters at both sides, only triangulation could do, but would still require to track the mobile transmitter by moving optics.

The other surprizing point is, that resolution or accuray requirement has never been discussed, although it is the most critical application parameter to my opinion.

Interesting suggestions anyway.

 

[mohamednabil84]

Re: How to measure distance?

you can combine both rf and ultra-sound solutions, an rf signal is sent from one point to tell the other point to start sending the ultra-sound signal, then when received by the first point, the time delay is known so the distance can be calculated. (the delay of the rf can be neglected since distance is short)