Speed measurment
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Posts: 46,084
Can ultrasonic transducers be used to determine the speed of a object
or vehicle?
Basically send out a pulse or string of pulses and recieve back the
doppler shifted pulses and then determine the difference in
frequency.
What kind of range can I expect from this type of technology?
I do have a July 1995 issue of Popular Electronics that has a
schematic and layout for a RF based radar gun like the police use
except in the x band. I could hack into this circuit and use a stamp
but I wanted to keep it simple, somewhat cheap and keep the FCC away.
The range of measurment would be from .5 to 25 MPH, distance to the
ground would be 3 to 5 feet, and the the median used to bounce back a
signal would be a plowed field with corn stalks and leaves flapping
in the breeze, that would be worst case.
I could filter out flapping leaves with a band pass filter for the
known measuremnt range.
Would this work?
Jason
or vehicle?
Basically send out a pulse or string of pulses and recieve back the
doppler shifted pulses and then determine the difference in
frequency.
What kind of range can I expect from this type of technology?
I do have a July 1995 issue of Popular Electronics that has a
schematic and layout for a RF based radar gun like the police use
except in the x band. I could hack into this circuit and use a stamp
but I wanted to keep it simple, somewhat cheap and keep the FCC away.
The range of measurment would be from .5 to 25 MPH, distance to the
ground would be 3 to 5 feet, and the the median used to bounce back a
signal would be a plowed field with corn stalks and leaves flapping
in the breeze, that would be worst case.
I could filter out flapping leaves with a band pass filter for the
known measuremnt range.
Would this work?
Jason
Comments
SRF04 modules.
BUT, you could do a number of quick pulses and collect some distances then
do a calculation of the distance changes over the time period.
Original Message
From: "jbirnsch" <jbirnsch@v...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, March 30, 2004 6:40 PM
Subject: [noparse][[/noparse]basicstamps] Speed measurment
> Can ultrasonic transducers be used to determine the speed of a object
> or vehicle?
>
> Basically send out a pulse or string of pulses and recieve back the
> doppler shifted pulses and then determine the difference in
> frequency.
>
> What kind of range can I expect from this type of technology?
>
> I do have a July 1995 issue of Popular Electronics that has a
> schematic and layout for a RF based radar gun like the police use
> except in the x band. I could hack into this circuit and use a stamp
> but I wanted to keep it simple, somewhat cheap and keep the FCC away.
>
> The range of measurment would be from .5 to 25 MPH, distance to the
> ground would be 3 to 5 feet, and the the median used to bounce back a
> signal would be a plowed field with corn stalks and leaves flapping
> in the breeze, that would be worst case.
>
> I could filter out flapping leaves with a band pass filter for the
> known measuremnt range.
>
> Would this work?
>
> Jason
>
>
>
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
> Yahoo! Groups Links
>
>
>
>
>
http://cigr-ejournal.tamu.edu/Submissions/PM%2001%20007.pdf
Jason
--- In basicstamps@yahoogroups.com, "jbirnsch" <jbirnsch@v...> wrote:
> Can ultrasonic transducers be used to determine the speed of a
object
> or vehicle?
>
> Basically send out a pulse or string of pulses and recieve back the
> doppler shifted pulses and then determine the difference in
> frequency.
>
> What kind of range can I expect from this type of technology?
>
> I do have a July 1995 issue of Popular Electronics that has a
> schematic and layout for a RF based radar gun like the police use
> except in the x band. I could hack into this circuit and use a
stamp
> but I wanted to keep it simple, somewhat cheap and keep the FCC
away.
>
> The range of measurment would be from .5 to 25 MPH, distance to the
> ground would be 3 to 5 feet, and the the median used to bounce back
a
> signal would be a plowed field with corn stalks and leaves flapping
> in the breeze, that would be worst case.
>
> I could filter out flapping leaves with a band pass filter for the
> known measuremnt range.
>
> Would this work?
>
> Jason
In simple words, they have a gate that is wide enough to collect 1
cycle/Hertz for each mile of hour of doppler speed sensed. (based upon the
formula and frequency of operation). This is about 32.xx Hertz per mile of
hour radial speed, at 10.525 GHz (as I remember). This gives the usual +/-
1 mph accuracy<G>. This makes a phase detector not necessary, though in
honesty, the mixer could still be considered one<G>.
They use a homodyne transceiver, which means that a portion of the
transmitted signal is sampled back and used for the local oscillator
frequency. Any drift in the Gunn diode circuit is small enough to not
affect accuracy (after warm up time), and slow enough to not affect the
transmitted signal/lo relationship.
It's simple to build. However, if you are measuring a complex object, or an
object in a complex area of reflections, hold on to your hats. The police
units which I have seen (I have a manual and schematic) look for 5
consecutive counts of the same number. Then this is "declared" to be a
valid speed. So far, I have found this to be the case, in that the only
times that I have seen the beast lie was in extremely heavy traffic,
starting off at a green light, and with big trucks nearby.
If you are using standard ultrasonic transducers, circuits using them for
other things should give you an idea of range. I think that I remember 20'
being max for unaided ones. But you could put one up on a reflector, like a
feedhorn, and use it like radar<G>.
Original Message
From: SB [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=qIl14gAO9w13V1yD_Uj8mGaEWDZM69DWypcMpp-vLPlPZYIwUqHiz42yZfcyAnhP8-6uZN1SrMmpgC_VjJen]steve.brady@r...[/url
Sent: Tuesday, March 30, 2004 6:43 PM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Speed measurment
you'd have to add some super het/phase detectors....not on their own as the
SRF04 modules.
BUT, you could do a number of quick pulses and collect some distances then
do a calculation of the distance changes over the time period.
Original Message
From: "jbirnsch" <jbirnsch@v...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, March 30, 2004 6:40 PM
Subject: [noparse][[/noparse]basicstamps] Speed measurment
> Can ultrasonic transducers be used to determine the speed of a object
> or vehicle?
>
> Basically send out a pulse or string of pulses and recieve back the
> doppler shifted pulses and then determine the difference in frequency.
>
> What kind of range can I expect from this type of technology?
>
> I do have a July 1995 issue of Popular Electronics that has a
> schematic and layout for a RF based radar gun like the police use
> except in the x band. I could hack into this circuit and use a stamp
> but I wanted to keep it simple, somewhat cheap and keep the FCC away.
>
> The range of measurment would be from .5 to 25 MPH, distance to the
> ground would be 3 to 5 feet, and the the median used to bounce back a
> signal would be a plowed field with corn stalks and leaves flapping in
> the breeze, that would be worst case.
>
> I could filter out flapping leaves with a band pass filter for the
> known measuremnt range.
>
> Would this work?
>
> Jason
>
>
>
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject
> and
Body of the message will be ignored.
>
> Yahoo! Groups Links
>
>
>
>
>
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
Yahoo! Groups Links
signal from the vehicle then use a basic distance over time to calculate speed.
For an example most Fords use 8000 pulses per mile (GM and Chryslers use 4000
pluses per mile you can check with your local dealer for more info) so if the
vehicle is traveling at 60 mph the VSS is generating 133.3333 pulses per second
(if my math is correct) this is well within the range of the stamps.
Brian
jbirnsch <jbirnsch@v...> wrote:Found some of my answers doing a google
search:
http://cigr-ejournal.tamu.edu/Submissions/PM%2001%20007.pdf
Jason
--- In basicstamps@yahoogroups.com, "jbirnsch" wrote:
> Can ultrasonic transducers be used to determine the speed of a
object
> or vehicle?
>
> Basically send out a pulse or string of pulses and recieve back the
> doppler shifted pulses and then determine the difference in
> frequency.
>
> What kind of range can I expect from this type of technology?
>
> I do have a July 1995 issue of Popular Electronics that has a
> schematic and layout for a RF based radar gun like the police use
> except in the x band. I could hack into this circuit and use a
stamp
> but I wanted to keep it simple, somewhat cheap and keep the FCC
away.
>
> The range of measurment would be from .5 to 25 MPH, distance to the
> ground would be 3 to 5 feet, and the the median used to bounce back
a
> signal would be a plowed field with corn stalks and leaves flapping
> in the breeze, that would be worst case.
>
> I could filter out flapping leaves with a band pass filter for the
> known measuremnt range.
>
> Would this work?
>
> Jason
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and Body of
the message will be ignored.
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[noparse][[/noparse]Non-text portions of this message have been removed]