Subject:
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Re: thoughts on dragsters
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Newsgroups:
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lugnet.org.ca.rtltoronto
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Date:
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Thu, 8 Mar 2001 02:43:21 GMT
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Viewed:
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529 times
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On Wed, 7 Mar 2001 05:18:45 GMT, Chris Magno <cmagno@home.com> wrote:
> I'm a little confused by what you asked here.
Strictly speaking, I wasn't so much asking as musing out loud. In
doing so, I was probably proceeding from a false assumption...
(snip)
> What did you mean by:
>
>
> I'm also assuming that only input 2 can be used for the
> light sensor
This may be the false assumption. I got it in my head a while back
that only input 2 could be used for active (powered) sensors. Hence
only input 2 could be used for light or rotation sensors. I take it
this is incorrect.
>
> --------------------
> You can put any sensor on any input.
(I wish I knew where I got that idea from - I'm sure I read it
somewhere)
> As to the last part, your "could" put 2 light sensors in parallel on one
> input but you will only get a reading for the sensors that is detecting
> the most light.
Unfortunately, while I have the RIS 1.0 (and 1.5 arrives tomorrow), as
well as the RDS, DDK, DSDK and UAS, I've never actually built anything
with it. As a techno-geek of sorts, this is killing me, but I promised
myself I would clean up my Ham radio and electronics related work
areas before I started spreading Lego everywhere, so there it all sits
in the cupboard beside the 2m radio....
The end result is that I have a lot of ideas, accumulated from many
sources (mostly here), but no practical experience. Once the idea of
input 2 as the only active sensor input got into my head, I began to
realize that the idea of a dragster that starts at the wall, goes to a
line and returns to the wall would be that much more complicated if
you could only use one active sensor at a time. If this isn't true,
then life gets that much easier.
I haven't taken the light or rotation sensors apart yet (can't see how
to do it without breaking the case) so I don't know how they're built,
but I would assume, given that the power and sensor data have to be
sent over only two wires, that the RCX is putting out a known voltage
and the sensor is using it to power the internal circuitry while
placing a variable load on the wires that is proportional to the input
data.
> ergo:
>
> if you have one point at the sun, and the other in your pocket, the
> value that will be displayed on the brick will be 96% (ish) this sort
> of negates the second sensor in the dark.
If my guess as to the inner workings of the light sensors is correct,
then placing two units in parallel would place their loads in parallel
and the RCX would see it as one sensor with a load that is higher than
either of the sensors by themselves. How this is interpreted depends
on whether a high load corresponds to a high brightness or high
darkness condition. I believe that your statement that you would only
get a reading from the sensor that is detecting the most light is not
accurate. It would not be possible to obtain a reliable reading from
either sensor.
As for the rotation sensor, given that this is also an active sensor,
my idea that only input 2 can be used for active sensors would
preclude using the rotation sensor with a light sensor at the same
time. Again, if in fact all the inputs can use active sensors, then
this won't be the case.
Lastly, you weren't sure about the temperature sensor. I don't have
one either, but thermistors are common and (relatively) cheap (I have
several, in fact). I strongly suspect that that is what is in the Lego
temperature sensor. A thermistor, in case you aren't familiar with
them, is a resistive element with a high temperature coefficient. That
is to say, it's resistance changes significantly over a small
temperature range. They are inherently passive.
Matthias Jetleb
VA3-MWJ
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Message is in Reply To:
 | | Re: thoughts on dragsters
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| (...) HI: I'm a little confused by what you asked here. all sensors can be used at the "same time" as every other sensor. the RCX can run up to 10 separate tasks. it would not be hard for the brick to have task 1 watch a light sensors on input 1, (...) (24 years ago, 7-Mar-01, to lugnet.org.ca.rtltoronto)
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