Subject:
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Re: A neat idea for touch sensors
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 4 Oct 2000 12:43:36 GMT
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Viewed:
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587 times
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"Rob Stehlik" <Robbby31@Hotmail.com> writes:
>
> I was trying to figure out a way to distinguish between
> two touch sensors on the same port. I have seen a lot of
> examples on the Web of sensor multiplexers using
> resistors.
> Being somewhat of a purist, I wanted to do the same thing
> with just Lego. Hmmm, as far as I know, lego doesn't make resistors.
There are the Cybermaster touch sensors with resistors,
but that's a rather expensive solution.
> But, I realized that lights are really just fancy
> resistors. So I hooked up a couple of Lego lights to a
> touch sensor, and voila, the two touch sensors give
> different readings when pressed.
Your idea is both simple and great and I just wonder why
nobody thought of it before. So how to get more lights?
I just have one from the Ultimate Accessory Set.
> I thought some of you might find this useful
> or just plain interesting. I tried to include a small DAT
> file to show exactly how they are hooked up, but the
> server said that the robotics newsgroup does not accept
> DAT files. So in words, with the touch sensor facing
> forwards, stick two lego lamps on top (where the electric
> contacts are of course!) with the lights facing out either
> side of the touch sensor. Then stick the wire on top of
> the two lights, with the wire facing back. I hope this
> makes sense.
From this description I think you get the following circuit diagram
(correct me if I'm wrong):
)----O------*
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\
\
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)----O------*
^ ^ ^
RCX lamps touch sensor
It seems that you are using two lamps where one should suffice,
with another short cable to make the proper connection.
Also, if you multiplex this sensor with an ordinary one, you
won't be able to distinguish whether only the ordinary or both
sensors have been pressed, I suppose. Can you try that?
A good way to connect things is like this:
)------------------*-----*
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R1 T1
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*-----*
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...
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*-----*
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Rn Tn
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)------------------*-----*
Here the Ri are resistors and the Tn are the touch sensors.
Then two combinations of presses on the touch sensors can be
distinguished if the sums of their resistors are different.
The resistors can be made by putting lamps in parallel or
series, so you'll need at least three lamps to have two
completely independent sensors, and five lamps for three
sensors (1 single, 2 in series, 2 in parallel).
I use the same kind of wiring for combining the three
cybermaster sensors, which have the resistors integrated,
and it works well. The light should allow me to use a
fourth sensor with these three.
You can make the necessary connections by using cables and
overlapping them only halfway. Also, the connections needn't be
directly on the sensor, using a cable on the sensor and doing the
circuitry on the other end is often better.
Good luck
Jürgen
--
Jürgen Stuber <stuber@loria.fr>
http://www.loria.fr/~stuber/
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Message has 2 Replies:
 | | Re: A neat idea for touch sensors
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| Hi Juergen, (...) I realize that I am using two lights where I only need one. Its just simplest to connect both lights to one sensor. I think I came up with a scheme to use only one light, but the wiring was somewhat convaluted. (You want the light (...) (24 years ago, 4-Oct-00, to lugnet.robotics)
| | | Re: A neat idea for touch sensors
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| (...) Those resistors in the Cybermaster touch sensors are in parallel to the sensor. You can read its value when the sensor is not pressed. Cybermaster uses it to figure out which sensor is connected to what port before starting the actual program. (...) (24 years ago, 4-Oct-00, to lugnet.robotics)
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Message is in Reply To:
| | A neat idea for touch sensors
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| Hi everyone, I was trying to figure out a way to distinguish between two touch sensors on the same port. I have seen a lot of examples on the Web of sensor multiplexers using resistors. Being somewhat of a purist, I wanted to do the same thing with (...) (24 years ago, 4-Oct-00, to lugnet.robotics)
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