Pulito – Featuring DFlex

Over the summer we installed hardwood flooring – which needs constant sweeping and cleaning .    What to do…  What to do…  Well, most of us would just sweep it, right?  Some of us might even go buy a Roomba.  But, then again, some of us build something to do it for them.  Why?  Because we can…

Pulito (Italian for ‘clean’) is simply put, a sweeper robot. Much like a Swiffer and Roomba combined.  The intent was to build a robot that could navigate around sweeping hard surface floors, stay away from carpeted areas,  make its way under our couches and seek out a docking station when the battery runs low.


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Old School Touch Sensor Multiplexing on the NXT

I find that I am often using this approach for getting more touch sensors on my NXT without using multiple ports.  So, for the sake of prosperity, I wanted to keep a record of the setup.

If you are have a set of Cybermaster Touch Sensors hanging around, you can multiplex them for use on the NXT.   Years ago, these sensors were quite rare, but now they can be readily found on Bricklink for a decent price.  For those that are unaware of these sensors, they are the trans-green (clear) touch sensors that come with the Cybermaster kit and look similar to the standard MINDSTORMS RIS ones, but with one significant difference – each of them have an inline resistor so that when the circut is closed, each passes  current with a different resistance.  In addition to this, the value returned varies depending on which combination of sensors is pressed.  So, not only can you detect individual sensors, you can also detect states of multiple sensors being pressed.    If my memory serves correct, you can detect 6 sensor states (1, 2 or 3 | 1 and 2 | 2 and 3|  1 and 3 )

You can program these sensors easily by setting them up as temp sensors using RAW values. You will get values between  0 – 1023.  You can also code in such a way that you are looking for specific values (eg 655), as when a sensor is pressed, the resistance returns an exact value (it does not float between a number range).  Also dont forget that you will need an NXT to RCX converter cable.



Cybermaster Touch Sensor Multiplexer



Sample RobotC program:


#pragma config(Sensor, S2,     multiTouch,          sensorLightInactive)
task main()
{
while(true){
nxtDisplayTextLine(1, “Val: %d “,SensorRaw(multiTouch) );
wait1Msec(20); //give the CPU a break.
eraseDisplay();
}
}

Sample NXT-g program:
NXT-g Cybermaster Touch Sensor Multiplexer

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