Recommended Distance Detection Method?

[Chris S]

Hi, I'm trying to create 2 components such that one can tell the distance it
is from the other over a limited range. The first component will essentially
be fixed, while the other can and will move quite rapidly (up to approx 20cm
in 0.1 seconds). The fixed component needs to know how far away the other
one is.

My requirements are:
1) The detection range needs to be between 5cm and 200cm
2) I need accuracy within ~5cm
3) The moving component needs to be quite light and small (<3cm)
4) The moving component could be in any direction from the fixed unit
5) I need to carry on receiving the info even if other entities get in
between the 2 components
6) The system needs to be as cost-effective as possible
7) The system needs to be able to operate in environments such as the living
room
8) Due to the speeds involved, I need to be able to update the detection at
least 10 times per second, and more than that if at all possible.
9) I may end up with more than one of these systems in the same area, so
being able to have unique frequencies or ID's would be a final requirement.

I'm guessing that IRDA is out due to requirement 4), and that I can't use
ultrasound due to 5). Does this leave me with RF modules as the only viable
option? If so can I use the strength of the signal to work out the distance
between the 2 objects? (I've never played with RF before...)

Any help would be much appreciated,

C.

 

[KevinR]

On Fri, 16 Jul 2004 11:08:24 +0100, "Chris S"
<chris@swanfamily.e7even.com> wrote:

Hi, I'm trying to create 2 components such that one can tell the distance it
is from the other over a limited range. The first component will essentially
be fixed, while the other can and will move quite rapidly (up to approx 20cm
in 0.1 seconds). The fixed component needs to know how far away the other
one is.

My requirements are:
1) The detection range needs to be between 5cm and 200cm
2) I need accuracy within ~5cm
3) The moving component needs to be quite light and small (<3cm)
4) The moving component could be in any direction from the fixed unit
5) I need to carry on receiving the info even if other entities get in
between the 2 components
6) The system needs to be as cost-effective as possible
7) The system needs to be able to operate in environments such as the living
room
8) Due to the speeds involved, I need to be able to update the detection at
least 10 times per second, and more than that if at all possible.
9) I may end up with more than one of these systems in the same area, so
being able to have unique frequencies or ID's would be a final requirement.

I'm guessing that IRDA is out due to requirement 4), and that I can't use
ultrasound due to 5). Does this leave me with RF modules as the only viable
option? If so can I use the strength of the signal to work out the distance
between the 2 objects? (I've never played with RF before...)

Any help would be much appreciated,

C.

Stick a three axis accellerometer in the moving thing, and have it
stored in a holster which is a known distance/angle from the
stationary point and use the holster as the datum.

Then, you can use whatever wireless comms method you like and
either process accelerometer info in the moving component and send
positional data, or send raw accelerometer data and calculate
positional in the stationary component.

 

[Chris S]

That sounds like an ideal solution - many thanks Kevin

C.


"KevinR" <me@privacy.net> wrote in message
news:5m2gf0hfkfrkn48eermv5faa1b09h1g4ar@4ax.com...

On Fri, 16 Jul 2004 11:08:24 +0100, "Chris S"
chris@swanfamily.e7even.com> wrote:

Hi, I'm trying to create 2 components such that one can tell the distance
it
is from the other over a limited range. The first component will
essentially
be fixed, while the other can and will move quite rapidly (up to approx
20cm
in 0.1 seconds). The fixed component needs to know how far away the other
one is.

My requirements are:
1) The detection range needs to be between 5cm and 200cm
2) I need accuracy within ~5cm
3) The moving component needs to be quite light and small (<3cm)
4) The moving component could be in any direction from the fixed unit
5) I need to carry on receiving the info even if other entities get in
between the 2 components
6) The system needs to be as cost-effective as possible
7) The system needs to be able to operate in environments such as the
living
room
8) Due to the speeds involved, I need to be able to update the detection
at
least 10 times per second, and more than that if at all possible.
9) I may end up with more than one of these systems in the same area, so
being able to have unique frequencies or ID's would be a final
requirement.

I'm guessing that IRDA is out due to requirement 4), and that I can't use
ultrasound due to 5). Does this leave me with RF modules as the only
viable
option? If so can I use the strength of the signal to work out the
distance
between the 2 objects? (I've never played with RF before...)

Any help would be much appreciated,

C.


Stick a three axis accellerometer in the moving thing, and have it
stored in a holster which is a known distance/angle from the
stationary point and use the holster as the datum.

Then, you can use whatever wireless comms method you like and
either process accelerometer info in the moving component and send
positional data, or send raw accelerometer data and calculate
positional in the stationary component.