help me to identify this microcontroller. please :(

[JonSea]

You haven't stated the range of distances you're attempting to measure. The speed of light table below is from Wikipedia and will help put things in perspective.

Light will travel 1 meter in ~3.3 nano-seconds – 3.3 x 10^-9 seconds. So to measure 1 meter, you must transmit a pulse, respond to the pulse with the receiving end to transmit a return pulse in some fixed, known time, sense the received pulse and measure Δt with nano-second resolution.

A microprocessor running at 20 MHz has a clock cycle of 5 x 10^-8 seconds....

Looks like a problem.

The speed of sound in air is 343 meters/second, roughly a million times slower than the speed of light. A bit more practical to measure I should think.

 

[atferrari]

Yes, it is going to be one of those LONG threads...

 

[Rafael143]

thanks

 

[Rafael143]

thanks

 

[JonSea]

First quantify what you're trying to measure then worry about the hardware.

What distance are you trying to measure?

What is the needed resolution?

Will the proposed method work for this? What resolution do you need on the time measurement? Is this practical to measure using whatever skills you have?

Only after the above questions are answered, start to select the hardware.


I think you're going to find that this approach isn't entirely practical. Maybe it is, but you need to understand the theory first.

 

[Rafael143]

thanks

 

[DerStrom8]

Rafael, you're trying to use a microcontroller and you don't know what "resolution" means?

I think you have some major catching up to do before you can even begin to think about how to make this project work....

 

[Rafael143]

thanks

 

[Rafael143]

thanks

 

[Nigel Goodwin]

You've been through all this on your other thread - including a link to an existing project - but basically you don't.

 

[alec_t]

i want to measure the time when the receiver received the signal

The device you need is called a clock

 

[DerStrom8]

Rafael143 , one thread is enough. I have merged your two threads together.

 

[alec_t]

To put things in perspective, the round-trip time for an RF signal to/from a target at 100m is ~600nS. To measure that sort of distance to the nearest metre would require a time resolution of ~6nS; i.e. you would need to be able to distinguish between two events only 6nS apart.

 

[Rafael143]

alec_t thanks man. your the best
.

 

[JonSea]

To put things in perspective, the round-trip time for an RF signal to/from a target at 100m is ~600nS. To measure that sort of distance to the nearest metre would require a time resolution of ~6nS; i.e. you would need to be able to distinguish between two events only 6nS apart.

I thought I said this already.....

 

[alec_t]

I must have missed that, Jonsea. Which post? AFAIK it wasn't until post #26 that 100m was mentioned.

 

[DerStrom8]

I'm still trying to figure out why that post was "funny"....

 

[JimB]

Yes, it is going to be one of those LONG threads...

atferrari summed it up nicely.

JimB

 

[JonSea]

Alec, I mentioned that an RF signal will travel 1m in ~3.3 nano-seconds in post #21. You spelled it out more directly.

I'm afraid a subtle answer isn't going far in this conversation.

 

[Rafael143]

thanks