LM565 as phase comparator/detector - Page 2 - Electronic Circuits Projects Diagrams Free

**Nigel Goodwin** · 1st October 2009, 11:35 AM

Quote:

Originally Posted by Mr CCE

- First of all, it's not like it's never been done before; Distance measurement through RF is used in many applications.

Not using licence free radio modules it isn't.

Quote:

- Second of all, have U ever tried it? i don't so. If I were able to get an indication that two objects are distant from each other by a variable x, then this variable can absolutely be used or perhaps utilized in such a way to estimate, up to a certain accuracy, the distance in question.

If you think it's so easy, feel free to do it

Do the maths, and work out the speed and precision you need.

Mr CCE · 5th November 2009, 08:18 AM

hey there everyone,

I've been trying with my project lately and I came up with these results:

1- My first approach was to use Signal power as a parameter to be utilized to determine distance.This did not go well since I'm using a ready made RF transmitter with a range of 3000 Km!! so obviously no change in power would be detected.

2- Second, I tried the phase detector consisting of an XOR + RC(low-pass filter) but I got a constant reading so I need someone to tell me how to choose the values of R and C (probably I chose wrong values

).

3-Now I'm planning on calculating the round trip time to figure out distance as follows:

TX1 ----> RX2
RX1 <---- TX2

where I will use a Microcontroller to start a timer as soon as TX1 sends the data and the timer will stop as soon as RX1 receives a confirmation signal.

but I need some advice to pull this off so it would be greatly appreciated, and I know that all of U guys are professionals, so any advice would really help.

thx in advance.

mneary · 5th November 2009, 12:01 PM

Your data is 2.4kHz, and you're running the sent and received signals through a phase detector. The propagation (wavelength if you will) is about 12 km. One eighth of that (round trip, 90 degrees) is 40km. So your phase detector gives you 0-Vcc from a measured distance of 0-12km.

2) Using 5V as Vcc, and assuming your timing on the phase detector is set to maximize the slope, your phase detector should give you a voltage delta of (5V/12km) or about 400 microvolts for a one meter distance change. Can you consistently measure 400 microvolt changes? It would require a 4-1/2 digit multimeter, for example, to measure to the nearest meter. Your phase detector power supply should be stable to 100 parts per million to avoid introducing spurious results.

3) Using a timer, assuming a 10MHz clock rate, each tick of the timer equals a round trip distance of 30 meters (round trip 15 meters). That's your basic resolution, assuming a perfect transmitter/receiver..

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5th November 2009, 08:18 AM	#17
Mr CCE	About the RF distance measurement thing.. hey there everyone, I've been trying with my project lately and I came up with these results: 1- My first approach was to use Signal power as a parameter to be utilized to determine distance.This did not go well since I'm using a ready made RF transmitter with a range of 3000 Km!! so obviously no change in power would be detected. 2- Second, I tried the phase detector consisting of an XOR + RC(low-pass filter) but I got a constant reading so I need someone to tell me how to choose the values of R and C (probably I chose wrong values). 3-Now I'm planning on calculating the round trip time to figure out distance as follows: TX1 ----> RX2 RX1 <---- TX2 where I will use a Microcontroller to start a timer as soon as TX1 sends the data and the timer will stop as soon as RX1 receives a confirmation signal. but I need some advice to pull this off so it would be greatly appreciated, and I know that all of U guys are professionals, so any advice would really help. thx in advance.

5th November 2009, 12:01 PM	#18
mneary	Your data is 2.4kHz, and you're running the sent and received signals through a phase detector. The propagation (wavelength if you will) is about 12 km. One eighth of that (round trip, 90 degrees) is 40km. So your phase detector gives you 0-Vcc from a measured distance of 0-12km. 2) Using 5V as Vcc, and assuming your timing on the phase detector is set to maximize the slope, your phase detector should give you a voltage delta of (5V/12km) or about 400 microvolts for a one meter distance change. Can you consistently measure 400 microvolt changes? It would require a 4-1/2 digit multimeter, for example, to measure to the nearest meter. Your phase detector power supply should be stable to 100 parts per million to avoid introducing spurious results. 3) Using a timer, assuming a 10MHz clock rate, each tick of the timer equals a round trip distance of 30 meters (round trip 15 meters). That's your basic resolution, assuming a perfect transmitter/receiver.. __________________ de KI6RWX Last edited by mneary; 5th November 2009 at 12:02 PM.