Intro to Electronics in Python

Intro to Electronics in Python
Anna Gerber

Electricity
•  Electricity is a form of energy
•  We can connect components that convert
electrical energy into other forms of energy:
light, sound, movement, heat etc, into a circuit
•  In a Direct Current (DC) circuit, 
electrical energy ﬂows from  
the positive side of a  
power source to the 
negative side, i.e. from  
+ (power) to – (ground)
Anna Gerber

Electrical concepts
•  Current (Amps): measures the flow of electrical
energy through a circuit
•  Voltage (Volts): measures difference in potential
energy between the positive and negative sides
of a circuit
•  Resistance (Ohms): measures a material's
opposition to the flow of energy
•  Power (Watts): the rate at which energy is
converted from one form to another
Anna Gerber

Ohm's Law
Current = Voltage / Resistance
•  Increase the voltage, and the current will
increase (i.e. speed up)
•  Increase the resistance and the current will
decrease
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Sensors
•  Environmental
condi/ons

(e.g.
temperature,
humidity,
smoke)

•  Magne/c
(e.g.
hall
eﬀect
sensor)

•  Light
(e.g.
photo
resistor)

•  Sound
(e.g.
microphone)

•  Mo/on
(e.g.
accelerometer,
/lt,
pressure)

•  User
/
Physical
Input
(e.g.
buDon)

Anna Gerber

Actuators
•  Light
&
Displays
(e.g.
LED,
LCD)

•  Sound
(e.g.
Piezo
buzzer)

•  Mo/on
(e.g.
Servo,
DC
Motor,
Solenoid)

•  Power
(e.g.
Relay)

Anna Gerber

Digital vs Analog
•  Digital
–  discrete values (0 or 1)(LOW or HIGH)
–  Examples: tilt sensor, push button, relay, servo
•  Analog
–  continuous values
–  Examples: photo resistor, DC motor
•  Some sensors support both digital and analog
outputs
Anna Gerber

Using a Breadboard
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•  Use to prototype circuits without soldering by
plugging in components and jumper wires
•  Letters and numbers for reference
•  Numbered rows are connected
•  Some have power bus along the sides

Resistors
•  Introduces resistance, so restricts the amount of
current that can ﬂow through a circuit
•  Coloured bands indicate resistance
•  Can be connected in either direction
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LEDs
•  Light Emitting Diode
•  Polarized: diodes act like one way valves so
must be connected in a certain direction
•  Emits light when a current passes through
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Anode
(+)

longer
lead

connects
to
power

Cathode
(-‐)

connects
to
ground

Control
•  Arduino-compatible
Microcontroller co-
ordinates robot inputs
(sensors) and outputs
(actuators)
•  See http://arduino.cc/
Anna Gerber

PyFirmata
•  https://github.com/tino/pyFirmata
•  Communicates with the Arduino using the Firmata
protocol
Install using pip:
pip
install
pyfirmata

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Loading Firmata onto the Arduino
•  Once-oﬀ setup to prepare our Arduino for use
with PyFirmata:
–  Connect the microcontroller board via USB
–  Launch Arduino IDE and open the Firmata sketch
via the menu: File
>
Examples
>
Firmata
>

StandardFirmata

–  Select your board type (e.g. Arduino Nano w/
ATmega328) via Tools
>
Board

–  Select the port for your board via Tools
>

Serial
Port
> (the port of your Arduino)  
e.g. /dev/tty.usbserial-A9GF3L9D
–  Upload the program by clicking on Upload

–  Close the IDE
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BLINKING AN LED
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Connecting an LED to the Arduino
•  Unplug the Arduino!
•  Attach long lead of
LED to pin 13 of
Arduino
•  Connect resistor to
cathode of resistor
and ground rail of
breadboard
•  Connect GND pin of
Arduino to ground
rail of breadboard
using a jumper wire
Anna Gerber

Creating the program
1.  Create a Python program ﬁle (e.g. blink.py)
2.  Edit it using a text editor e.g. SublimeText
3.  At the start of your program import the library

import
pyfirmata

Anna Gerber

Creating the board
We create a Board object which corresponds to our
Arduino-compatible microcontroller board and store it
in a variable.
We need to provide the port as a parameter:
board
=
pyfirmata.Arduino("/dev/tty.usbserial-‐A9QPTF37")

Anna Gerber

Controlling the LED
•  Then we can control the LED via the pin it is
connected to (in this case, pin 13)
•  Use a variable for the pin number to make it easier to
change later
–  PIN
=
13

•  Turn on LED on pin 13
–  board.digital[PIN].write(1)

•  Turn oﬀ LED on pin 13
–  board.digital[PIN].write(0)

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Delayed behaviour
•  Use the pass_time function to delay functions
by a certain number of seconds e.g. blink LED
on then oﬀ after one second:

board.digital[PIN].write(0)

board.pass_time(1)


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Repeating behaviour (loops)
Use a while loop to blink indeﬁnitely:
while
True
:


board.pass_time(1)


board.pass_time(1)

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The entire blink program
import
pyfirmata

PORT
=
"/dev/tty.usbserial-‐A9QPTF37"

PIN
=
13

board
=
pyfirmata.Arduino(PORT)

while
True:


board.pass_time(1)


board.pass_time(1)

Anna Gerber

Running the program from Terminal
•  Open the Terminal app
•  Change directory to the location where you have
saved your code e.g.  

>
cd
~/Desktop/code/

•  Run your program using Python e.g. 

>
python blink.py 
•  Hit control-C to stop the program
Anna Gerber

Connecting to iPython Notebook
•  We will use iPython Notebook running on
Raspberry Pi
•  Plug into Raspberry Pi via ethernet (connect to
DHCP server on Pi)
•  Open 192.168.1.1:8888 in your browser
Anna Gerber

How to setup the software at home
•  Install Arduino IDE
–  Optional, only required if you want to load
Firmata again or experiment with programming
the Arduino using C++
•  Install Python
•  Install PyFirmata

• 
Install a code editor e.g. Atom (Mac only),
SublimeText if you don't already have one or
install iPython Notebook
Anna Gerber

Where to ﬁnd out more
•  Electricity
–  https://www.khanacademy.org/science/physics/
electricity-and-magnetism/v/circuits--part-1
•  Arduino Playground

–  http://playground.arduino.cc/interfacing/python
•  Sample code for Freetronics kit
–  https://gist.github.com/AnnaGerber/
26decdf2aa53150f7515
Anna Gerber

Intro to Electronics in Python

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