Subject:
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Re: rotation sensor
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Newsgroups:
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lugnet.robotics
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Date:
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Sun, 21 Dec 2003 20:07:11 GMT
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Viewed:
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986 times
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In lugnet.robotics, Thomas Kronschläger <loop_flyer@web.de> wrote:
>
> Hi !
>
> I'm gonna include the lego rotation sensor to a c167 system
> created by myself and for that I need to know
> which pins of the lego plug function for what.
>
> As far as I know the plug of the rotation sensor has two pins
> for power supply and another two for the signal, but now I need
> to know who is who.
>
> I would be glad if somebody could help me.
> Excuse my bad english.
Hi Thomas,
Your english is better than my danish. No need to apologize.
There are only two wires between the RCX and the rotation sensor. These wires
provide both power and sensor signal.
There are two kinds of sensors: passive and active.
Touch sensors are passive, in that they do not have to be powered with lots of
voltage or current to work. The RCX has an analog to digital converter that it
time multiplexes between things like the sensor inputs and battery level.
For passive sensors, the RCX sends a very low current signal to the sensor and
uses the A/D converter to tell what the reading is. It does this every 3
milliseconds for a given sensor input. The RCX has a built in resistor in
series with the sensors. The A/D convertor reads the voltage across this
resistor. When the touch sensor is open (unpressed) no current goes through the
resistor, so there is no voltage drop. When the touch sensor is closed then
current can flow, and there is voltage drop across the resistor.
Active sensors need to be powered with higher voltage and current than passive
sensors. The light sensor and rotation sensor are active sensors. They have
little electronic circuit boards inside their brick. For most of the 3ms
reading cycle, the RCX sends power to the sensor to be able to power the
electronics. For a very small part of the 3ms read cycle, the RCX acts like it
is reading a passive sensor. It turns off the high current power (max of about
6-7mA), and reads the value like it would for a passive sensor. The RCX assumes
that the sensor electronics will use a capacitor (that gets charged up during
the power on part of the cycle) to keep the electronics powered during the
passive reading part of the read cycle.
Your home brew circuit will need to mimic the RCX's passive/active cycle
behavior if it is going to try to read values from the rotation or light
sensors.
I highly recommend you study this site to get pointers to a wonderful book, as
well as descriptions of how the RCX works, and how to make your own home brew
sensors.
http://www.plazaearth.com/usr/gasperi/lego.htm
The "Extreme Mindstorms" book is a fabulous read, especially the sensor section.
Let me know if there are other ways I can help.
Kevin
>
> Best regards,
Thomas
Best regards,
Kevin
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Message is in Reply To:
 | | rotation sensor
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| Hi ! I'm gonna include the lego rotation sensor to a c167 system created by myself and for that I need to know which pins of the lego plug function for what. As far as I know the plug of the rotation sensor has two pins for power supply and another (...) (21 years ago, 21-Dec-03, to lugnet.robotics)
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