Analog Multiplexer for NXT touch sensor by STAAK


STAAK posted on the Polish LUGPOL forum an nice instruction guide in How to build a touch sensor multiplexer.




He describes:" For both multiplexers I used resistors with values 32k, 10k, 68k, and 150k. The NXT touch sensor already have a built-in additional 2.2 k resistor.

By design, the two multiplexers (RCX, NXT) will work with the NXT via a single block in NXT-G. Because the use of the internal resistors (and the same precision resistors), I needed to create a block for the NXT-G that allows the thresholds to be set by the user. Normally when you insert a block to the project can be seen only as the left side of the settings. Select the checkbox will show a window for manually setting the appropriate thresholds.

Block Parameters:
Port: 1 to 4 = the Port connected on the NXT
Limit: 1 to 6
TH1000 for threshold limit of 5 = 520 indicates that this threshold is detected in the range 515 < TH1000 < 525.
Threshold: 0 to 1023

Drop-down box in the left window is used only for viewing a given threshold value.
A threshold value is nothing more than the raw value for the relevant states of the configuration of sensors

TH1011 should be read as TH Sensor1=1 Sensor2=0 Sensor3=1 Sensor4=1 where
Sensor1 = in series with 10k resistor
Sensor2 = in series with 32k resistor
Sensor3 = in series with 68k resistor
Sensor4 = in series with 150k resistor

The output signal from this block is the four outputs (T1-T4), True / False
where True state of the output indicates that the sensor is pressed.

After setting the threshold check block, save the project.
The Copy/Paste option allows you to insert the block into a new project together with the pre-set thresholds.

Click here to download the block.




The cost of the multiplexer elements was less than 2$ for the resistors
The NXT-G block was written in LabView with the overlay LabVIEW Toolkit for LEGO MINDSTORMS NXT available on the National Instruments.

see also his Brickshelf folder.

Well done STAAK!

Comments

Trella said…
Will this Multiplexer be for sale somewhere?