1. How to avoid catching things on fire.
Electronics 101
How to avoid catching things on fire.

2. Bread Boards

3. Connect a Blue LED to pin D7 and a Red LED to pin D0

4. Your Photon's Pins Voltage Input (also USB power) ground
serial communication
wake up
Digital - Analog Conversion
Analog
Input
and
Output
3.3 Volts output
reset (when grounded)
battery input
ground
built-in LED
digital input
and
output

5. Voltage, Current, Resistance
amount of electrons moving through the circuit
Measured in Amps (A)
Represented by “I” in equations
Voltage
Amount of push
Measured in Volts (V)
Resistance
Amount of resistance
Measured in Ohms (Ω)
V = I * R
Ohm’s Law

6. Voltage, Current, Resistance
Particle Photon
Input Voltage
micro USB – 4.8 Volts
or the VIN pin – between 3.3 and 5.8 VDC (VDC = volts direct current)
Current Consumption
80mA when WiFi is on ( 80mA = 80 milli Amps = 80/1000 of an Amp)
Output Voltage
3.3 Volts (3V3)
Output Current
25mA per pin
250mA total

7. Voltage, Current, Resistance
Short Circuits
Remember : Current = Voltage / Resistance
What happens to Current if Voltage remains 3.3, but Resistance goes very low?
Amps = 3.3V / Ohms

8. LEDs -- Light Emitting Diode
LEDs create almost no resistance, so you must use a resistor with an LED
Without a resistor, the current would spike and burnout the LED and perhaps damage the controller unit
The resistor can be placed before or after the LED
Long wire goes to positive
Short wire to negative or ground
LED Varieties:
5mm, 8mm
Diffuse, not diffuse IR
RGB

9. Resistors

10. Pull Up Resistor Bad Bad Design:
Everyone will use this.
Bad
Bad Design:
When the button is pressed, the pin will go low.
But when the button is not pressed, the pin floats.
We need to "pull" the pin high when the button is open.
We need a resistor to prevent a short.
The standard is 10kΩ
So commonly used that your Photon has Pull Up resistors built in on all input pins.
Good
pinMode(D5, INPUT_PULLUP); // Enable internal pull-up resistor on pin D5

11. Pull Up Resistor Example
These break sensors and door sensors are "normally open" switches.
they work just like buttons
To get reliable input, we must use a pull-up resistor.
Opening the door opens the switch, which causes the pin to go to HIGH.
Closing the door closes the switch, so power goes LOW.
Closed = Low
Open = High

12. Pull Up Resistor Example
Turn on an LED when the door is open.
Breadboard:
connect one sensor wire to ground
other sensor wire to an input pin, like A4
Code:
void setup() {
pinMode (D7, OUTPUT); // built-in LED
pinMode (A4, INPUT_PULLUP); // input pin }
void loop()
int value; // value from sensor
value = digitalRead(A4); // read input pin
digitalWrite (D7, value); // turn LED on or off

13. DAC and ADC Digital to Analog Analog to Digital Example:
Probably not necessary,
because your Photon has
both Digital and Analog
inputs and outputs.
Digital to Analog
Example:
Control the speed of a motor.
You send the DAC chip a number from 0 to 255 and it outputs a voltage from 0 to 9 volts to make the motor speed up or slow down.
Analog to Digital
Input voltage from a light dimmer switch and convert the value into a number.

14. Not many projects
will use this.
N Channel MOSFET
Problem : Suppose you need to turn 12 Volts on and off for a fan motor or a long string of LEDs
Your Photon only outputs 3.3 volts
12V would fry your Photon
Solution : Use a MOSFET as a switch
one pin on the MOSFET (gate or base pin) connects to an output pin on your Photon
turn the Photon pin on and off to turn the 12V on and off
two other pins on MOSFET (drain and source) go in your 12V circuit
Be Careful :
Read a tutorial before wiring.
Size determines Voltage and Amps.
They get hot!
The 12V ground and the Photon ground must be connected.

15. Capacitors Electric Storage Device Measured in Micro Farads Uses:
A few projects
will use this.
Electric Storage Device
Measured in Micro Farads
Uses:
Smooth out a power supply
Smooth signal noise

16. Digital Display Boards
Necessary when using
Digital Display Boards
I2C

17. De-Multiplexer Multiplexer is the opposite.
Extremely unlikely
you will need this.
Suppose you want to turn on 1 of 8 different LEDs, but don’t want to use 8 different Output Pins.
Sending 000 to the chip turns on its output pin 0.
Sending 001 turns on its pin 1. …
Sending 111 turns on pin 7.
Multiplexer is the opposite.
8 input pins and 3 output pins.

18. Questions?