Basic Electronics

How do I hook up a ________ to my ________circuit?

+ V -

Electricity in a circuit• Potential

Volts [ V ]

• Current

Amps [ A ]

• Resistance

Ohms [ Ω ]

• Power

Watts [ W ]

R

I

+ V -

Electricity in a circuit• Potential

Volts [ V ]

• Current

Amps [ A ]

• Resistance

Ohms [ Ω ]

• Power

Watts [ W ]

Fluid flow through pipe • “pressure”

• “rate of flow”

• “pipe length or diameter”

• rate of energy

Image: http://www.productionapprentice.com/

R

I

Combining Stuff

Series R (adds)

Rtotal = R1 + R2 + R3

Parallel R (decreases)

Rtotal =

1 / [1/R1 + 1/R2 + 1/R3]

Kirchoff’s Current Law: I out = I in

Node A: i2 = i3

Node B: I = I1 +I2 +I3

A

B

V = I * Rvolts = amps * ohmsvolts = mA * Kohms

OHM'S LAW

I

V R

+

-

Electrical Power (Watts) P = V * I = I2 * R = V2 / R

Circuit Analysis How-To:

1. Draw schematic (e.g battery, LED’s, etc.)

2. For each component: Write down what you know (V, I, R, or Pmax)

3. Use equations to get the rest: V=I*R, P=V*I, Iin = Iout, Ic = b*Ib,

4. Still missing a value? look it up on a datasheet or I-V curve and go

to step 2.

How much Current is flowing through this resistor?

I I = V/R = 9V/1K = 9mA = .009A

1/RI

V

resistor

Answer underneath

Diodes

• “One-way” Valve: only allows current flow in one direction

• Vdiode 0.6v (when “on”)

P-N Junction

V-I CurveIf |ID| > Imax“I’m on fire”

ID = 0“I’m off”

@ Vd < Vbreakdown, ID = is Negative“OK, I give up”

Using Diodes

• Limit Current (I < Imax)• Vdiode ~ 0.6v

NO!OK

Choose R >>(5v - .6)/ Imax

R= 4.4v/ 20mA = 220 Ohms

R=?(VR = 5v-0.6v

(V0.6v)

How do I hook up an _LED_ to my Arduino circuit?

Which of These Work?

330 10K 3300

OK NOPE:Not Enough

Current

NOPE:LED

Backwards

NOPE:Answer underneath

LED Facts

• Only allows current in one direction (lights up)

• Only happy at particular voltage and current give it both– About 10 to 20mA– About 1.7V for Red LED’s – Check a datasheet for exact info

Other Colors:

I

V

OFFON happy

Von

1.5 V

On fire

anode

cathode

I

LED

+ 1.5 V -

Wants ~10 mA

I = ??

mA 6.10330

5.15

R

VI

Other Colors:

10-20mA or More

Answer underneath

digitalWrite(0,HIGH); // applies 5V to pin 0delay(1000); // waits a seconddigitalWrite(0,LOW); // applies 0V to pin 0

ARDUINO CONTROL OF LED

ARDUINO

PIN 0

GND

5V

0V

20 mA max

Crucial

anode

cathode

I

LED’s off a battery?

+ 1.5 V -

Vbattery

R = ??Other Colors:

10-20mA or More

Vbatt 3.3v 5v 9v 12v

R10mA= 160 330 730 1K

RVR=Vbatt-Vcolor

Vcolor=?Idesired=?

R = (Vbatt – Vcolor)/IdesiredAnswer underneath

Wants ~10 mA

Light 3 LEDs via 1 Pin

ARDUINO

PIN 0

GND

5V

0V

20 mA max

Need 30 to 60 mA & 3 Resistors

Only draws 10 to 20 mAOnly needs 1 resistor

Chose R = (9v – 3*1.7)/11mA

How do I hook up a _____* to my Arduino circuit?

*Anything other than an LED

DEVICEPIN 0

GND

5V, 20 mA

ARDUINO

What if device needs more than 5V ormore than 20 mA??

…Need Arduino-actuated Switch

Computer controlled switch

DEVICE

V big

ARDUINO

PIN 0

GND

I big

LOAD: MOTOR, SOLENOID, RELAY, LAMP, …

I

V

ON

OFF

Arduino

Transistorcurrent-controlled amplifier, current-controlled switch

I big = b*I smallI small

BASE COLLECTOR

EMITTER

Think: spray can!

BASE

EMITTER

COLLECTOR

Ic = b*Ib

Ib

Ie = Ib + IcONE-WAY!

5V

0V

LOAD: MOTOR, SOLENOID, RELAY, LAMP, …

I

V

I

V

ON

OFF OFF

ON

Vce sat0.1 – 2.0 V

Vbe 0.6v

+

-

Arduino

Arduino

(BJT) Transistors

• “One-way” Amplifier• Can use as an on-off switch

N-P-N Junction V-I CurveIf |Ice| > Imax“I’m on fire”

Ice = 0“I’m off”

IbI

V

OFF

ON

Vce sat0.1 – 2.0 V

Inside (BJT) Transistors

• 1 electron injected at base about 150 electrons flow at collector (exact number is called: )b

• Vbe 0.6v (just like a diode)• Vce 0.6 to 2v

N-P-N Junction

Ic = b*Ib

Ie = Ib + Ic

Ib

Vbe 0.6v

Vce 0.6v to 2v (see datasheet)

How do I hook up a _____* to my Arduino circuit?

*Anything other than an LED

5V

0V

OK NO!

Vbe=0.6v

Ib = (5-.6)V /1K = 4mA

Ib = (5-.6)V/ 0 = A

“I’m on fire”

Transistors Require a Resistor

Which Transistor?

TO-92 TO-220 TO-3

2N3904 TIP120

100 mA 1-2 A 20-50 A

Things to look for on a data sheet

• Max current, Ic max• Max volts, Vce max• Max power, P max• Vce sat• Gain: Hfe or b• Switching time

2N3904

TIP 120

Electronics Part II

…w/ Demo’s

Interfacing to Motors

Hook motor straight to Arduino?

Motor interface

FOR SMALL MOTOR, USE 2N3904

Pin 2

GND+-

Pin 2

GND+-

Arduino pin limits

10.6 mA

4.4 mA 1 A

20 mA per PIN40 mA TOTAL

POWER

+

V

-

I P = V * I

P = ??

I = V/R = 9/10 = 0.9 A

P = V*I = 9*.9 = 8.1 WAnswer underneath

I

P = 12 * I

, t w

I, VHEAT

WOW! WHAT A GREAT MOTOR I GOT AT AX-MAN! AND IT RUNS ON

12v!

Later…

12V

YOUCH!!IT'S HOT!

5 V

Ib

Ic

mA 4.41000

6.00.5

bi

Vce sat ~ 2.0 VLet Ic = 5 A

PWR = V*I = 2.0*5 = 10 W !!!

HOT

wasted

5V

0V

LOAD: MOTOR, SOLENOID, RELAY, LAMP, …

I

V

I

V

ON

OFF OFF

ON

Vce sat0.1 – 2.0 V

RELAYS

To control larger loads

Relays• Electromagnet-controlled switch• User for (1) larger loads, (2) bi-directional motor

COIL control side12V, 120 ohm, 100 mA5V, 500 ohm, 10 mA

CONTACTS load side240 VAC/28 VDC, 10 A100 VDC, 1A120 VAC/24 VDC, 0.5 A/1.0A

COIL CONTACTS

Types of relays

GENERAL PURPOSECOIL: 12, 24 VDC; 120 VACCONTACTS: 5-10 A

REEDCOIL: 5, 12 VDCCONTACTS: .5-2 A

SOLID STATECOIL: LOGIC INPUTCONTACTS: 2-25 A

JAMECO 174431

COIL: 12 V, 400 OHM, I = V/R = 12/400 = 30 mACONTACT: 24 VDC, 15 A

Transistor drive for a relay

NOTE: RELAY COIL CAN SUCK CURRENT

SOLENOIDS

For linear, short-range, on-off motion

x

F

¼ in.

Force when energized

x

MAX ON-TIME = ½ SEC

www.jameco.com

Switches

SPST SPDT

(NO, NC)

#define MOTOR 0#define SWITCH 4...

digitalWrite(MOTOR,HIGH); delay(1000); // wait for motor to clear switch while (digitalRead(SWITCH) ; digitalWrite(MOTOR,HIGH);...

Read the rest in the on-line notes

WIRE

1. CONNECT POINTS OF EQUAL VOLTAGE2. CARRY CURRENT

SMALL WIRE+

HIGH CURRENT

STRANDED SOLIDFlexible Higher current

Type Gauge Max I Notes

Wrap wire 30 200 mA wrapping, signal level only

Hookup 24/22 1-2 A general purpose

Lamp cord 18 5 A

House wire 14/12 15/20 A

“CABLE” = multiconductor wire bundlee.g. modular phone cord: 28g solid, 4 conductor

BATTERIES• Primary

– Zinc– Alkaline (most

common)– Lithium (camera,

watch)• Secondary

(rechargeable)

– Sealed lead acid (car)

– Gel– NiCd– NiMH– Lithium

• Important specs

– Energy density– Voltage

• Zinc/Alkaline: 1.5 V• Lead Acid: 2.0 V

– cars: 6, 12 V• NiCd: 1.2 V

– Power tools: 4.8, 6.0, 7.2, 9.6, 12, 18 V

– Maximum current• “Cold-cranking amps”

– Capacity• Amp-hours or mAHrs

Capacity and discharge• 12 V (10 cell) NiCd pack

rated at 1300 mAH

– 1.3 Amps for 1 hour – 520 mA for 2.5

hours…..in theory• Top-notch cells for RC

racing can provide 2300 mAH

• 9V alkaline

– 580 mAH @ 12 mA (can deliver 12 mA for 48 hrs)

Discharge curve

t

9V

Alkaline technology

See www.duracell.com (or other sites) for more

mA

Hrs

100

1

10010

Service life

Battery technologiesChemistry Energy density

(W-H/Kg) Cell voltage

NiCd 38 1.2

Lead Acid 40 2.0

NiMH 70 1.2

Carbon-Zinc 75 1.5

Alkaline 130 1.5

Lithium-Ion 130 3.7

Lithium-Poly 190 3.7

Lithium 300 3.0

www.hardingenergy.com