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Hi All,
One of the features of the LDCC firmware is the ability to read
the configuration variables out of a DCC decoder installed in
a train motor. In order to do this, you need to connect a small
circuit consisting of one or two resistors from the track
power to sensor input #1 on the RCX. Well, instead of
hacking up some Lego wires or electric plates, I've come up
with a simple design that's made of all Lego components:
http://www.brickshelf.com/cgi-bin/gallery.cgi?i=430557
It's basicly made of a touch sensor and a couple wires. The
blue 1x2 brick keeps the touch sensor depressed. There's an
internal resistor in the touch sensor of about 500 ohms and this
does the job handily. (Note: I'm not sure if the other touch
sensors Lego makes have an internal resistor, you should
check the resistance if you plan to use one of them).
The circuit is hooked up to the RCX in this fashion:
http://www.brickshelf.com/cgi-bin/gallery.cgi?i=430565
Note that the wires cross over each other when connected to
the RCX. It's important to get the wiring the same as in the
photo so the wire polarities are correct and the circuit will work.
You won't harm the RCX if the wires coming off the RCX are
oriented incorrectly or reversed. However, on the touch sensor
side, you must connect the wires exactly as shown. You don't
want to do the following:
http://www.brickshelf.com/cgi-bin/gallery.cgi?i=430560
which is essentially the same as connecting a wire from the
output directly to the input. Your RCX will probably not
like you for that... :-/
While reading back the configuration variables isn't necessary
to run your trains, it makes life easier when you want to start
taking advantage of some of your decoder's extra features.
Enjoy,
Mark
LDCC Page: http://home.surewest.net/markril/lego/dcc/
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Message has 1 Reply:
 | | Re: All Lego Ack Circuit for LDCC
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| (...) All touch sensors I measured have a "pressed" resistance between 400 and 600 ohms (depends on touch sensors and on pressure, more pressure meaning lower resistance). Actually there is no separated resistor, you get the internal resistance of (...) (21 years ago, 18-Jun-03, to lugnet.trains, lugnet.robotics.rcx)
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