project founded by an idea

[evilstrike]

I have had an Idea for a project that involves a signal transmiter & receiver.
The project consist of using a transmiter that sends a signal to the receiver who thens somehow calculate the distance between the transmiter and the receiver.
There is no preference as to what mesurement the distance is to be calculated, just as long as its possible to determine if the distance if less or more then a predefined distance
for example
the predefined distance is set the 10meters
the receivers or the transmiter should be able to determine if the current distance between them is lower or higher then 10meters.

Anyone know any similar devices or any information site that contains data relavent to this project? What would be the best type of transmiter & receiver to acheive something like this? And I would assume it would require some chip programming for the distance measuring?

any information would be usefull
thx

 

[SPDCHK]

I don't think what you've just described is possible.

There's no time reference, i.e. the receiver has NO idea of when the signal was originally sent. (For all it (the receiver) knows the signal could have come from the moon). All the receiver will do, is receive the signal. If the receiver itself has a re-transmitter circuit to relay the signal back to the original Tx, then you're in business, but that will mean you should have a Tx,Rx set on both sides of the measurement range.

(Correct me if I'm wrong)

 

[stevez]

If the transmitter and receiver had clocks that were precisely synched it's possible. What you might want to do is the math to see how long it takes for a signal to travel 10 m. That will give you a sense of what you might be dealing with in terms of time - and from there you need to see and react to the differences.

 

[akg]

but you will need a tight sync.

 

[evilstrike]

but that will mean you should have a Tx,Rx set on both sides of the measurement range.

Indeed, I was mostlikly thinking about relaying it back to the transmiter (well to the receiver on the transmiter side)
Although for now, im going to start just by trying to get the receiver to get the distance between it and its transmiter

If the transmitter and receiver had clocks that were precisely synched it's possible

I have never really played with transmiters but if I understand what you are saying, the signal when being transmisted contains sometype of timestamp?
If so then the receiver could read the time at which the signal was sent and in return substract it from received time which would provided a value that could possibly be used to calculate a distance in time?

This would mean that instead of trying to determine distance to be in meters, I could do it using miliseconds or seconds? besing that for example a 50 second delay could be equal to 10meters? If the delay is below 50 seconds its below 10meters and about 50 seconds is above 10meters

but you will need a tight sync.

As for the sync goes (if I understood the top part correctly) the 10meters does not have to be exactly precise. Thus if the clock were not completly in sync, It would not matter so much as long as it is still possible to determine if the distance is close enough to the range.

Is this somewhat correct or am I completly blinded by my own imagination? hehe

Are there any devices, toys, gadgets etc.. that any of you are aware that does some type distance calculation from a transmiter to a receiver?

thanks

 

[stevez]

If you had two clocks that were synchonized so that you had the resolution and accuracy you require (yet to be defined) you might transmit a burst that includes the precise time of some part of the burst. The receiver would compare that time - adjusting for other delays and processing - and the difference will be proportional to the distance. Unless I misplaced a decimal the time for light to travel 10 meters is about 0.03 microseconds.

If I am not mistaken, GPS works with multiple signals from satellites to calculate a position - and those signals contain the timestamps I envision. In any event, what you are proposing is nothing new and I presume you are aware of that - and your effort is more about coming up with your own, simpler device. I recall that LORAN or other navigation aids used time pulses but it's been a while since I read about that stuff.

 

[Nigel Goodwin]

This would mean that instead of trying to determine distance to be in meters, I could do it using miliseconds or seconds?

I agree with 'stevez', you're talking nanoseconds and picoseconds, NOT milliseconds - you're talking VERY complicated, and VERY, VERY expensive.

 

[HiTech]

you're talking VERY complicated, and VERY, VERY expensive.

An undertaking that only American taxpayers see their money get wasted on.

 

[Nigel Goodwin]

An undertaking that only American taxpayers see their money get wasted on.

The UK taxpayers see lots of their money wasted as well, and we generally pay more tax than you!.

 

[philba]

The UK taxpayers see lots of their money wasted as well, and we generally pay more tax than you!.

yes but you get so much more back than us...

 

[Nigel Goodwin]

yes but you get so much more back than us...

Oh yes - we get the pleasure of seeing Tony Blair on the TV!.

 

[JimB]

An undertaking that only American taxpayers see their money get wasted on.

There were a series of programmes on TV by a Professor Adam Hart-Davis, the titles of the programmes were:

What the Romans Did For Us

What the Victorians Did For Us

What the..... you get the idea.

If there were to be a programme "What The Americans Did For Us", for me GPS would be up there near the top.
Thank you America for GPS!

JimB

 

[HiTech]

Perhaps it's time for a "Tea Party"?

 

[The Mad Professor]

Does this project have to operate at radio freaquencies ?

Sound waves would provide a more suitable medium of transmission, of course 10meters is right on the limit for small "hobby" ultrasonic transducers so rangefinding by using a reflected signal may not be reliable.

However as the sound waves would effectively heard at the target reciever ,( after all its only the weakness of the return echo that limits the range) ,what can be detected, can trigger a responce, the target could broadcast its own signal back to the base unit. The doppler shift between outgoing and incoming signals at these low freaquencies can be handled by the existing ultrasonic rangefinder circuits found on web.

 

[philba]

Does this project have to operate at radio freaquencies ?

Sound waves would provide a more suitable medium of transmission, of course 10meters is right on the limit for small "hobby" ultrasonic transducers so rangefinding by using a reflected signal may not be reliable.

However as the sound waves would effectively heard at the target reciever ,( after all its only the weakness of the return echo that limits the range) ,what can be detected, can trigger a responce, the target could broadcast its own signal back to the base unit. The doppler shift between outgoing and incoming signals at these low freaquencies can be handled by the existing ultrasonic rangefinder circuits found on web.

not a bad idea at all. I'd set it up to echo a received pulse and measure the total flight time (send time, return time, response computation time). doppler only works for moving objects. One problem to solve is the directional nature of US devices. maybe use multiple Tx and Rx.

 

[evilstrike]

Does this project have to operate at radio freaquencies ?

No because I was actually asking for a trasmiter & receiver but I didnt specify if it had to be RF. This is a self project so I have no rules or limit, it can use whatever works. So it can be IR, RF, Wireless, Bluethooth or whatever other method that exist. The only limit that I would have is that im not rich hehe and I have no skills in chip programming but I am a software programmer so I do know how to programm, just never programmed a chip for that matter which is why im trying to find if something like this already exist that I can used or modify to do what I would require it to do

By the way im not trying to invent something that calculates distance, I want to used something that calculates distance for the main project that I have. And so if something like this already exist it would be great as I would not have to fiddle too much with this.

As for GPS goes, woulndt I need a GPS transmiter to transmit the coordinates back at the host? Because this project involves 2 devices and one of the 2 devices needs to take action if the distance between each device exceeds a certain distance. Using GPS I would have to find a way to relay the GPS coordinates back at the host and they somehow calculate the distance with the given values which im not to sure how that can be done.

Right now though im trying to gather as much idea and information as I can to find out the best way to tackle this.

However as the sound waves would effectively heard at the target reciever ,( after all its only the weakness of the return echo that limits the range) ,what can be detected, can trigger a responce, the target could broadcast its own signal back to the base unit. The doppler shift between outgoing and incoming signals at these low freaquencies can be handled by the existing ultrasonic rangefinder circuits found on web.

Do you have and site on hand that can provide this method in greater details?

 

[The Mad Professor]

Nature has solved your problem for you, lower frequency sounds propogate omnidirectionaly and travel further better. Your project has a lot in common the frogs. When one "croaks" , another nearby will answer. Few years ago there was a circuit kicking about that duplicated this behaviour.

 

[HiTech]

are you suggesting he obtain two bullfrogs then to be used as emitter and receiver? Suppose one hops away?

 

[AllVol]

How does the Distance Measuring Equipment in aircraft navigation systems work. Isn't that basically what he is asking about?

 

[dknguyen]

How does the Distance Measuring Equipment in aircraft navigation systems work. Isn't that basically what he is asking about?

They use an echo radar (as opposed to two distant transmitters and receivers talking to each other, which I guess would just be called RF). ANd the answer is still the same- it's impossibly hard for an individual with limited amounts of money to build radar rangers.