# needs to find distance between two moving objects

Discussion in 'Homework Help' started by electrazy, Jan 19, 2009.

1. ### electrazy Thread Starter Member

Jan 19, 2009
21
0
how i can measure distance between two moving objects without placing any part of circuit/apparatus at other object
are there any sensors that can serve the purpose
distance is around less than 10 meter
more details

some apparatus that can be developed in lab using sensor ic transmitter etc

....ok let me make it very simple , for eg.- we have to measure the distance between two moving cars (any vehicle) moving with variable speed

while the full apparatus is in the car running behind no part of device is placed on car in front

car in front can be made of any material (reflector or non reflector) and can be of any shape

both cars are in same plane

assuming relative speed to be 1-16 meter per sec

info is required in real time and output should voltage or current and proportional to distance

distance must be measured continously(as it is changing with changing speed)

max distance between them can be 8-10 meter

Last edited: Jan 20, 2009
2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
You can transmit ultrasonic waves from one object to another and measure the time the wave will reflect and come back. Then you can calculate the distance because the speed the wave travel is constant.

3. ### jpanhalt AAC Fanatic!

Jan 18, 2008
5,676
899
Stanley Tools sells a laser range finder that will work from 1 to 30 m easily. It is sold under the FatMax brand and is based on TOF. John

4. ### electrazy Thread Starter Member

Jan 19, 2009
21
0
but dont u think it might be expensive as i need it for my project
any IC or sensor u can suggest and any more suggestion for developing the circuit

5. ### electrazy Thread Starter Member

Jan 19, 2009
21
0
i need to find the distance for my project .the apparatus should continously measure the variable distance (as both objects r moving with variable speed)
and gives voltage or current output proportional to distance

6. ### jpanhalt AAC Fanatic!

Jan 18, 2008
5,676
899
With the edited spec of 10m, ultrasound becomes more feasable. Your original requirement of 30m is quite a bit more difficult to meet with ultrasound.

Regardless of what method you use, you will be measuring the relative distance for specific defined periods. With sound, you will have significant temperature effects, doppler effect (you could get relative velocity from tha directly), and change in position during the round trip time for the sound. Light is relatively insensitive to temperature, and TOF will have insignificant error due to change in position during the measurement, unless the items are moving very fast. If they are moving that fast, you won't be able to use sound anyway.

At what relative velocities will the objects be moving?
John

7. ### Bernard AAC Fanatic!

Aug 7, 2008
4,170
395
My choice would be the Stanley, otherwise you'll need a bunch of parts, a schematic, lots of time, an oscilloscope,maybe calibrated high frequency oscillator, and lots of luck. I've included my rough intrepitation of a block diagram, starting with a ultrasonic transducer op. around 60kHz.if you can find one.

File size:
125.7 KB
Views:
56
8. ### electrazy Thread Starter Member

Jan 19, 2009
21
0
....ok let me make it very simple , for eg.- we have to measure the distance between two moving cars (any vehicle) moving with variable speed

while the full apparatus is in the car running behind no part of device is placed on car in front

car in front can be made of any material (reflector or non reflector) and can be of any shape

both cars are in same plane

assuming relative speed to be 1-16 meter per sec

info is required in real time and output should voltage or current and proportional to distance

distance must be measured continously(as it is changing with changing speed)

max distance between them can be 8-10 meter

Last edited: Jan 20, 2009
9. ### electrazy Thread Starter Member

Jan 19, 2009
21
0
what is basically your principle behind that schematic
and how 1 count = 1 cm

10. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
513
You really need to start with a much more comprehensive and tighter spec.

Call the mobiles mobile A and mobile B, with A allowed to carry electronics.

What weight can A carry?

Do the mobiles move along pedifined paths and are they confined to a plane?

Is there always line of sight or are there obstacles?

Can mobile B carry passive kit such as a reflector, eg sticky metal tape?

Where and in what form should the information (readout) be available?

Is the information required in real time or will a log with subsequent processing suffice?

Can the information be relayed for processing to a third box eg a laptop?

Can the information be calculated from an external network of sensors, tracking the two objects and relaying to a third device for calulating the position on the grid of both objects and thus their distance apart?

Alternatively what materials can everything be made of? Could you for instance arrange for A and B to be two metal objects moving on a specially prepared floor like two Daleks, and measure the capacitance between them?

Depending upon funding options you may well be able to modify an optical mouse or pc IR system as a possible cheap option.

I suggest you go through the spec with you project supervisor and beef it up, before settling upon a particular avenue.

11. ### electrazy Thread Starter Member

Jan 19, 2009
21
0
....ok let me make it very simple , for eg.- we have to measure the distance between two moving cars (any vehicle) moving with variable speed

while the full apparatus is in the car running behind no part of device is placed on car in front

car in front can be made of any material (reflector or non reflector) and can be of any shape

both cars are in same plane

assuming relative speed to be 1-16 meter per sec

info is required in real time and output should voltage or current and proportional to distance

distance must be measured continously(as it is changing with changing speed)

max distance between them can be 8-10 meter

Last edited: Jan 20, 2009
12. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Perhaps this is an application for DGPS (differential global positioning satellite). You would need to have a GPS receiver on each of the vehicles. Each vehicle would take its GPS reading at synchronized intervals to make sure that the two readings had the same preprogrammed error in them. Each vehicle would receive the coodinates of the other vehicle via an RF link and compare this coordinate set with its own. Some fairly complex math would be needed to convert the coordinates into distance.

hgmjr

13. ### electrazy Thread Starter Member

Jan 19, 2009
21
0
GPS is not an option ....(some device or circuit that can be developed in a lab using sensors, ic, transmiter etc)
ok let me make it very simple ,

for eg.- we have to measure the distance between two moving cars (any vehicle) moving with variable speed

while the full apparatus is in the car running behind no part of device is placed on car in front

car in front can be made of any material (reflector or non reflector) and can be of any shape

both cars are in same plane

assuming relative speed to be 1-16 meter per sec

info is required in real time and output should voltage or current and proportional to distance

distance must be measured continously(as it is changing with changing speed)

max distance between them can be 8-10 meter

14. ### hgmjr Moderator

Jan 28, 2005
9,030
214
OK. So GPS is out of the question. If I come with another alternative I will propose it.

hgmjr

15. ### electrazy Thread Starter Member

Jan 19, 2009
21
0
details are

for eg.- we have to measure the distance between two moving cars (any vehicle) moving with variable speed

while the full apparatus is in the car running behind no part of device is placed on car in front

car in front can be made of any material (reflector or non reflector) and can be of any shape

both cars are in same plane

assuming relative speed to be 1-16 meter per sec

info is required in real time and output should voltage or current and proportional to distance

distance must be measured continously(as it is changing with changing speed)

max distance between them can be 8-10 meter

16. ### Bernard AAC Fanatic!

Aug 7, 2008
4,170
395
Are cars radio controlled? If so car A not only needs to calc. range but direction as well-remotely. Sounds like war games. Irradiate target with IR and detect with a series of IR detectors for direction?? Also what is speed of sound at your location ??

17. ### electrazy Thread Starter Member

Jan 19, 2009
21
0
details are

for eg.- we have to measure the distance between two moving cars (any vehicle) moving with variable speed

while the full apparatus is in the car running behind no part of device is placed on car in front

car in front can be made of any material (reflector or non reflector) and can be of any shape

both cars are in same plane

assuming relative speed to be 1-16 meter per sec

info is required in real time and output should voltage or current and proportional to distance

distance must be measured continously(as it is changing with changing speed)

max distance between them can be 8-10 meter

18. ### Bernard AAC Fanatic!

Aug 7, 2008
4,170
395
Still no answer to my questions. If you can derive a pulse representing two-way time from transmit to receive, gate on an oscillalor for that time period. Osc. frequency 17kHz, which gives one cycle per centameter. Count cycles and you have distance in cm.
For remote operation, use time pulse to gate an RF transmitter[key chain type around 433MHZ] Demodulated received signal can then be processed at receiver site.
I used speed of light ,sea level of 340 m/sec. 1/340X2=.0058822 s/m round trip, or .000058822 s/cm. Converting period to frequency; 1/ .000058822= 17kHz. or 1Hz=1cm.

19. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Bernard,

Did you mean "speed of sound" is 340 m/s instead of "speed of light"?

hgmjr

20. ### electrazy Thread Starter Member

Jan 19, 2009
21
0
j j j j j j j j j j