Subject:
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Re: Ultrasonic Sensor
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Newsgroups:
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lugnet.robotics
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Date:
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Sun, 18 Jan 2004 01:08:13 GMT
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Viewed:
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1270 times
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In lugnet.robotics, Mark Tarrabain wrote:
> Ismael Salvador wrote:
>
> > Hi all, I recently got an ultrasonic sensor from MindSensors, the problem is
> > that I don't have a stable value and they overlap with different distances.
> > Nitin suggested me to use alkaline batteries rather than rechargeable ones.
>
> That suggestion makes no sense at all given what your problem is. The
> voltage and current to the sensors is regulated by the electronics in
> the RCX, and is not governed directly by the type of battery that you
> are using. This would only make sense if the sensor itself had its own
> internal battery.
>
> > I have done it with both types and the result is nearly the same.
>
> I have not personally tried this particular sensor, but I don't find
> this very suprising. Ultrasonic detection is not very precise without
> extremely sensitive and expensive equipment (unless you are a bat). If
> you want a little more precise distance detection, I recommend using
> modulated IR and measuring that. If you want very precise distance
> detection, you may have to spend top dollar. Sorry.
>
> > > Mark
In my experience, the loss of "headroom" when using rechargeable batteries can
cause serious problems for active sensors. They run from a current limited copy
of the battery voltage when in the power phase of the active sensor interface
mode. If the sensor takes close to the maximum available current with fresh
batteries, then it may well fail to operate correctly with battery voltages
below about 8 volts. Once the diode and capacitor bridge system fails to fall
out of circuit during the measurement phase, power current starts to show up as
part of the reading and from there you're basically all done.
Sensor design for use with the RCX has as one of its prime directives - sip
juice!
JB
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Message is in Reply To:
 | | Re: Ultrasonic Sensor
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| (...) That suggestion makes no sense at all given what your problem is. The voltage and current to the sensors is regulated by the electronics in the RCX, and is not governed directly by the type of battery that you are using. This would only make (...) (21 years ago, 17-Jan-04, to lugnet.robotics)
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