The introduction to Arduino labs at Malmö University. These slides have been handed down since the beginning of Arduino. They have more authors then i can remember and should by no means be considered mine.

1. PHYSICAL PROTOTYPING
© 2011 K3 Creative Commons v3.0 SA-NC
Lab 5: Complex Sensors
With the Arduino prototyping board

2. SENSOR
• Device measuring information from the environment (the
world) and translating the values into data understandable
by our computers
• We can classify the sensors into two different groups,
according to how they send information back to the
microprocessors:
– ANALOG SENSORS: those that interface
microprocessors through the analog inputs, offering
signals varying between 0 and 5Volts
– COMPLEX SENSORS: those that communicate using
either digital pins with PWM, serial communication, I2C
or SPI (FYI: the last two methods are special types of
serial communication)

3. ANALOG SENSORS
• ANALOG SENSORS: within this group we distinguish two modalities:
– RESISTIVE/CAPACITIVE SENSORS: those that contain a
resistive/capacitive component that varies its value with light,
temperature, etc.
• LDR – Light Dependant Resistors
• Potentiometer: angle/stretch sensor
• NTC – Negative Temperature Coefficient (Temp. var. resistor)
• Flex-sensors
• Pressure sensors
• Piezo Elements: can act as knock sensors
– SIMULATED ANALOG SENSORS: complex sensors offering a
simple interface to microcontrollers.
• ACCELEROMETERS: to measure tilt, and movement
• InfraRed: to measure distances from 1mm to 80cm
• Humidity

4. COMPLEX SENSORS
Their main characteristic are that they communicate using
either digital pins with PWM, serial communication, I2C or
SPI (FYI: the last two methods are special types of serial
communication)
There are many sensors within this group of complex sensors:
– ACCELEROMETERS: the classic is the MEMSIC2125
broadly used in prototypes, lately people are hacking Wii
controllers
– GPS: sends strings over a Serial connection
– PING, SRF04/05: ultrasound devices measuring the
distance to objects using sonar technology
– Precise Temperature sensors

5. SENSOR vs. ACTUATOR
Keep in mind the following statement:
EVERY ANALOG SENSOR CAN BE USED AS
AN ACTUATOR AND VICEVERSA
•For instance the piezo element that will also act as knock
sensor
•This can be applied at low level only (simple sensors), so this
does NOT apply for complex sensors and simulated analog
sensors
•Actuators will also act as sensors, e.g. a DC motor is also a
dynamo, what makes it into an analog sensor to detect
movement

6. A COUPLE OF TRICKS
If, after connecting your components to an Arduino board...
•you lack some digital inputs for your buttons, you can always use
analog inputs and detect values over/under 512 instead of HIGH
or LOW
•you lack some analog inputs for an analog sensor that you only
use with a threshold, you can put it into a digital input, knowing
that you will only read HIGH or LOW and that the threshold will be
at 2,5 Volts, to change it, you can use a potentiometer instead of a
pull-up resistor for your sensor
•you lack pins in general, to use as inputs, you can always use
multiplexer circuits to add extra inputs. A recommended circuit to
use is the 4051, which is broadly documented, or the tlc5940
which has some very nice libraries and is also well documented

7. PRESENCE vs. DISTANCE
• Many projects aim to determine whether there are people or not
in a space
• Other projects try to determine the distance of people to objects
• Different types of sensors allow to measure both presence and
distance
• However we have to keep in mind that:
– presence implies to distinguish animated from inanimate
objects: THIS IS VERY COMPLICATED
– distance implies multi-resolutive systems: THIS IS VERY
COMPLICATED
• As designers we just make prototypes and we look into some
features from sensors that allow us to simulate the desired
functionality ... BUT WE WON'T MAKE IT WORK FOR REAL!

8. DISTANCE
There are different types of sensors that act very well
depending on the distance (range) we want to measure:
– InfraRed is very precise under 1m, there are some
sensors that concentrate in just 3cm!!
– Ultrasound is very precise up to 10m, but it is a slow
technology, we can only measure 5 samples/second
with the kind of technology we use for prototyping
(empirical values when using the sensor data in
software programs)
– LDRs can be used for rough measuring of touch
(many use it in their projects to simulate touch sensors)
or distances smaller than 5cm, but it has very low
accuracy

9. ACCELEROMETER
• Accelerometers are sensors that can measure different
things, among others they can measure the tilt of an
object carrying the sensor, if the object moves, how quick
it moves, etc.
• Accelerometers are very noisy sensors, therefore their
data is not very accurate, however with a correction it is
possible to make them very useful for 3-D positioning
• An example of a corrected sensor is the Wiimote, or basic
Wii's game controller. It contains a 3-D accelerometer with
an infrared camera that will measure the position of the
screen correcting the possible errors made by the
accelerometer
• Even if noisy, accelerometers can be very useful for quick
prototypes within interaction design

10. ACCELEROMETER
• The accelerometer we are using (MMA7260QT XYZ-axis
accelerometer) can measure 3 dimensions of the
movement that we call axis X, Y and Z
• The information comes in three analog pins which can be
measured with a microcontroller
• The device operates at 2.2 V to 3.6 V, which can make
interfacing difficult for microcontrollers operating at 5 V.
• Pololu
IMAGES © 2009 http://www.pololu.com

11. ACCELEROMETER
• Each of the three outputs is an analog voltage that ranges from 0
to Vcc. For 5 V applications, the outputs will range from 0 to 3.3 V
• The 3.3 V output can be used as a reference for analog-to-digital
converters to gain full resolution samples.
• The way how this particular sensor works is through a moving
bubble of gas inside the chip. Other types of accelerometers use
other micro and nano techniques to measure the sensor's tilt and
acceleration
PICTURE © 2005 ParallaxInc

12. Both jumpers on selects a range of +/-1.5g;
GS1 jumper on and GS2 jumper off selects: +/-2g;
GS1 jumper off and GS2 jumper on selects: +/-4g;
both jumpers off selects a range of +/-6g.
ACCELEROMETER

13. EXERCISE ►ACCELEROMETER
• Connect one of the Accelerometer sensors
to your Arduino board
• Test to see if it works
• Modify the code so that it sends the
following strings to the computer:
“LEFT”, “RIGHT”, “UP”, “DOWN” ...
basically you should transform your Arduino
into a tilt-pad

14. ULTRASOUND
• Ultrasound is a technology used for submarines, accurate
measuring of forms through human tissue, etc.
• Technically it is called SONAR
• We will use a cheap sensor (either PING or SRF05) to measure
the distance to objects
• The basic functionality works like this:
– the sensor emits a burst (signal)
– it enters listening mode
– the burst bounces on any objects and the signal travels back
– the sensor estimates the time it takes for the signal to come
back
– it sends a pulse to the microprocessor which width is in relation
to the signals flying time and therefore to the distance to the
object

15. ULTRASOUND
The signals of the SRF05 sensor look like this:

16. ULTRASOUND
The signals of the PING sensor look like this:

17. The difference between the SRF05 and the PING))) sensor is in
the amount of pins they have:
– the SRF02 sensor has one input and one output pin, as well
as a mode pin that allows to use it as the PING sensor
– the PING sensor only has three pins: 5V, GND, signal and
therefore it requires to use a pin both as input and as output
ULTRASOUND

18. EXERCISE ►ULTRASOUND

19. ULTRASOUND: COVERAGE
• The concept of coverage of a sensor is used to determine
the physical range where it will gather data
• E.g. a remote control will only communicate if it is pointing
towards the TV, this means that the coverage area of the
remote is only in front of it.
• Each sensor has a characteristic (unique) coverage range
• The coverage area of ultrasound sensors is not very narrow.
They have an opening angle of 20-60 degrees depending on
the type. The ones we use in class have an angle of about
50 degrees
• This means that we have to be careful when mounting the
sensor. It has to be almost sticking out of the object we
mount it on

20. ULTRASOUND: COVERAGE
• The following diagram represents the typical
coverage of an Ultrasound sensor
• You can see how it reaches furthest in front of the
sensor while it goes less far on the sides
PICTURE © 2006 Devantech

21. A matrix is used in LED displays to control many
outputs (LED’s) with few pins
Showing something on the LED display is done by
using a special pattern
This pattern makes use of the LEDs polarity (Its
ability to only conduct electricity in one direction)
LED displays are expandable by linking them to each
other
Instructables has a good instruction on how to do this
MULTIPLE OUTPUTS

22. MULTIPLE OUTPUTS

23. Turning one row of LED’s HIGH and one column LOW
will light up one LED
Switch between the rows really fast and the human
eye will think all of them are on all the time.
MULTIPLE OUTPUTS
Source: http://letsmakerobots.com/node/23980 Source: http://tacticaldesign.mit.edu/page/2

24. Multiple outputs
• You can create an LED display and interact with
it using an accelerometer.
• This can be done with either The Dawn board
or a Matrix board

25. USEFUL RESOURCES
• Shops:
– Sparkfun
– Electrokit
– Elfa
– Adafruit
• Information:
– Arduino
– Arduino playground
– Led wizard
– Instructables
– Resistor Calculator
– Analog Circuits
– Educypedia
• Inspiration:
– Youtube
– Flickr
– Google
– Yanko design
– We make money not art
– FFFFF
– Graffiti Research Lab