Connecting ScratchDuino.Lab and Selecting a Port in Scratch
In the Scratch window that appears, select the blue block Sensing, then right-click on the block Sensor and select show ScratchBoard watcher (see Fig. 7). Then right-click on the grey background and choose select serial/USB port (see Fig. 8). Select /dev/cu.usbmodem1411 in the drop-down list.
Components of the Kit
ScratchDuino.Lab (“Digital Laboratory”) is intended for laboratorial and illustrating experiments, research projects of the students, and hands-on training at the IT-classes and the lessons on natural sciences in primary and secondary schools, 5–11 grades.
The equipment includes:
¾ Arduino UNO microcontroller with the options of standalone operation and cinnection to a PC with monitor;
¾ built-in sensors (see Fig. 13);
¾ attachable sensors (Fig. 11), designed for metering the parameters of objects at study by the external devices.
Fig. 11. Attachable temperature sensor
and connecting cable with three crocodile clips.
Fig. 12. 180-cm-long cable to connect ScratchDuino.Lab to a PC.
Fig. 13. Components of ScratchDuino.Lab circuit board:
1— Sockets for additional analog sensors
(resistance-A and resistance-B variables [1] );
2 — Digital input for an external device*; 3 — Button (Button variable);
4 — Speaker; 5 — Controllable matrix of eight LEDs*;
6 — Three LEDs (red, yellow, and green), each at its own digital input*;
7 — Four buttons (resistance-A, resistance-B, resistance-C,
and resistance-D variables);
8 — Light sensor (Light variable); 9 — Sound sensor (Sound variable);
10 — Adjustable resistor (Slider variable).
* Additional items, for which a modified version of ScratchBoard is needed.
The kit also includes:
¾ the cable to connect the ScratchBoard to a PC (see Fig. 12);
¾ a CD with the software;
¾ User Manual;
¾ written guarantee.
Sensors Testing and Calibration
To be able to compose the programs, it is important to study the response of the sensors and the values taken by the buttons of ScratchDuino.Lab. Despite their being standard, the sensors in different kits of ScratchDuino.Lab can have their own individual ranges of sensitivity.
Table 1. Sensitivity Ranges and Values Taken by the ScratchDuino. Lab Buttons
| Sensor or button (name of the variable) | Min | Max |
| Light sensor (Light variable) | 12 | 98 |
| Sound sensor (Soundvariable) | 23 | 100 |
| Adjustable resistor (Slider variable) | 0 | 100 |
| Black button (Button variable) | false | true |
| Four buttons (resistance-A, resistance-B, resistance-C, and resistance-Dvariables) | 0 | 100 |
| Temperature sensor (when connected, uses the resistance-A variable) | 0,6 | 22,5 |
Calibration of L ight Sensor
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To calibrate a light sensor, a meter of illuminance is used. In our case, it is digital luxmeter LX101. The measurements shown in Table2 and in Fig. 14.
Table 2. Relation between the Meterage of ScratchDuino. Lab Light Sensor
and Luxmeter LX-101
| Luxmeter LX-101, lx | 1 | 3 | 11 | 22 | 37 | 42 | 53 | 63 | 75 | 83 | 92 | 110 | 220 | 320 | 440 | 562 |
| Light sensor | 12 | 47 | 60 | 65 | 67 | 67 | 69 | 70 | 70 | 71 | 72 | 73 | 75 | 82 | 86 | 90 |
Fig. 14. Area of linear dependency (confidence range)
between the Luxmeter LX-101 and the light sensor of ScratchDuino.Lab
meterage curves.
Using the Luxmeter LX-101 user manual’s guidelines on recommended level of luminance at working places (Fig. 15), it is possible to assume that the built-in light sensor of ScratchDuino.Lab can be with great confidence used as a luxmeter at a luminance of up to 100 lx calculated by Formula 1. This formula is obtained as per a trend line (approximation of the function) for the light sensor values from 12 to 73.
y = x - 15,62 (1)
confidence range of the sensor
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Fig. 15. Recommended luminance at working places
and the confidence range of ScratchDuino.Lab light sensor.
Calibration of Sound Sensor
The measurements are made in a room at complete silence. In this case the sensor indicates the value 23. The natural sounds (voice, music etc.) correspond to a range of 60–80. A maximum of 100 can be achieved when you make a vigorous breathing-out into the sensor. To identify the functional dependence of the sensor sound in decibels (dB), you need to use a digital phonometer. Methods of measurements and the derivation of a formula are similar to those described for the calibration of light and temperature sensors.
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