Ultrasonic position sensor

Started by paulcounter1 April 5, 2007
I am in the process of designing an ultrasonic position sensor, which
I will use to periodically re-zero the drift on an accelerometer
based position sensor.
I am trying to decide on a microcontroller to use in the device, so
my question is about the capabilities of the BasicX system (whether
24 or 01)
I am sure you are all familiar with the basic workings of ultrasonic
range finding so I won't go into that in any great detail. I will be
using 8 different ultrasonic recievers (4 at 25kHz and 4 at 40kHz).
There will be two transmitters (one for each frequency) which will be
triggered at the same time and then the time delay to each of the
recievers will be measured. Some fairly basic maths can then give me
both the position and a compensation for temperature effects on the
speed of sound.
I can see the BasicX24 has 8 seperate ADCs, but what I need to know
is whether all 8 can be read at the same time?
If they need to be read sequentially then I assume that there is no
simple solution other than having a simple microcontroller embedded
with each reciever to store the data and forward it on to the central
microcontroller. Or can anyone think of a different solution?

Many thanks for your help.
Paul C

P.S. If anyone thinks that there is a much better microcontroller for
my application then please let me know as I am not yet committed to
the BasicX, although it does seem the best option for a relatively
inexperienced person like myself.
Hi Paul,
The BX-24 has one (1) 10 bit ADC. It uses an eight channel analog
mux, so the "analog reads" would have to be sequential. It can "scan"
pretty fast so it may work for a "periodic application". Depending on
your transmitters, a digital output port pin should be able to
trigger them when you want to and the "math" capabilities are very
adequate.

You may want to consider an alternative approach using "digital
sonar" modules available in both 24KHz and 40KHz. This ultimately may
be the most cost effective approach and gives you interesting control
of the directionality, sensing patterns, and programming options.

GOOGLE the words BX-24 I2C

(1 of 744 hits) shows details of up to 16 "sonar modules", with
schematics and code examples.
http://www.robot-electronics.co.uk/htm/srf08bx24.shtml

Without further project specifications and parameters this is the
best I can do.

Best Regards, Eric

--- In b..., "paulcounter1" wrote:
>
> I am in the process of designing an ultrasonic position sensor,
which
> I will use to periodically re-zero the drift on an accelerometer
> based position sensor.
> I am trying to decide on a microcontroller to use in the device, so
> my question is about the capabilities of the BasicX system (whether
> 24 or 01)
> I am sure you are all familiar with the basic workings of
ultrasonic
> range finding so I won't go into that in any great detail. I will
be
> using 8 different ultrasonic recievers (4 at 25kHz and 4 at 40kHz).
> There will be two transmitters (one for each frequency) which will
be
> triggered at the same time and then the time delay to each of the
> recievers will be measured. Some fairly basic maths can then give
me
> both the position and a compensation for temperature effects on the
> speed of sound.
> I can see the BasicX24 has 8 seperate ADCs, but what I need to know
> is whether all 8 can be read at the same time?
> If they need to be read sequentially then I assume that there is no
> simple solution other than having a simple microcontroller embedded
> with each reciever to store the data and forward it on to the
central
> microcontroller. Or can anyone think of a different solution?
>
> Many thanks for your help.
> Paul C
>
> P.S. If anyone thinks that there is a much better microcontroller
for
> my application then please let me know as I am not yet committed to
> the BasicX, although it does seem the best option for a relatively
> inexperienced person like myself.
>