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: R I

Combining Stuff Series R (adds) R total = R 1 + R 2 + R 3 Parallel R (decreases) R total = 1 / [1/R 1 + 1/R 2 + 1/R 3 ] Kirchoff’s Current Law: I out = I in Node A: i 2 = i 3 Node B: I = I 1 +I 2 +I 3 A B

V = I * R volts = amps * ohms volts = mA * Kohms OHM'S LAW I V R + - Electrical Power (Watts) P = V * I = I 2 * R = V 2 / 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 P max ) 3.Use equations to get the rest: V=I*R, P=V*I, Iin = Iout, Ic =  *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?

II = V/R = 9V/1K = 9mA =.009A 1/R I V resistor Answer underneath

Diodes “One-way” Valve: only allows current flow in one direction V diode  0.6v (when “on”) P-N Junction V-I Curve If |I D | > Imax “I’m on fire”

Using Diodes Limit Current (I < Imax) Vdiode ~ 0.6v NO! OK Choose R >> (5v -.6)/ Imax R= 4.4v/ 20mA = 220 Ohms R=? (V R = 5v-0.6v (V  0.6v)

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

Which of These Work? 33010K330 0 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 OFF ON happy V on 1.5 V On fire

anode cathode I LED V - Wants ~10 mA I = ?? Other Colors: 10-20mA or More Answer underneath

digitalWrite(0,HIGH); // applies 5V to pin 0 delay(1000); // waits a second digitalWrite(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? V - Vbattery R = ?? Other Colors: 10-20mA or More Vbatt3.3v5v9v12v R 10mA = K R V R =Vbatt-Vcolor V color =? I desired =? R = (Vbatt – Vcolor)/Idesired Answer 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 mA Only 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

DEVICE PIN 0 GND 5V, 20 mA ARDUINO What if device needs more than 5V or more 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 

Transistor current-controlled amplifier, current-controlled switch I big =  *I small I small BASECOLLECTOR EMITTER Think: spray can!

BASE EMITTER COLLECTOR Ic =  *Ib Ib Ie = Ib + Ic ONE-WAY!

5V 0V LOAD: MOTOR, SOLENOID, RELAY, LAMP, … I V I V ON OFF ON Vce sat 0.1 – 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 Curve If |Ice| > Imax “I’m on fire” Ib I V OFF ON Vce sat 0.1 – 2.0 V

Inside (BJT) Transistors 1 electron injected at base  about 150 electrons flow at collector (exact number is called:  Vbe  0.6v (just like a diode) Vce  0.6 to 2v N-P-N Junction Ic =  *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 OKNO! Vbe= 0.6v I b = (5-.6)V /1K  = 4mA I b = (5-.6)V/ 0  =  A “I’m on fire” Transistors Require a Resistor

Which Transistor?

TO-92TO-220TO-3 2N3904TIP mA1-2 A20-50 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  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 PIN 40 mA TOTAL

POWER

+V-+V- I P = V * I P = ?? I = V/R = 9/10 = 0.9 A P = V*I = 9*.9 = 8.1 W Answer underneath

I P = 12 * I  I, V HEAT

WOW! WHAT A GREAT MOTOR I GOT AT AX-MAN! AND IT RUNS ON 12v!

Later… 12 V YOUCH!! IT'S HOT!

5 V Ib Ic Vce sat ~ 2.0 V Let 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 ON Vce sat 0.1 – 2.0 V

RELAYS To control larger loads

Relays Electromagnet-controlled switch User for (1) larger loads, (2) bi-directional motor COIL  control side 12V, 120 ohm, 100 mA 5V, 500 ohm, 10 mA CONTACTS  load side 240 VAC/28 VDC, 10 A 100 VDC, 1A 120 VAC/24 VDC, 0.5 A/1.0A COIL CONTACTS

Types of relays GENERAL PURPOSE COIL: 12, 24 VDC; 120 VAC CONTACTS: 5-10 A REED COIL: 5, 12 VDC CONTACTS:.5-2 A SOLID STATE COIL: LOGIC INPUT CONTACTS: 2-25 A

JAMECO

COIL: 12 V, 400 OHM, I = V/R = 12/400 = 30 mA CONTACT: 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

Switches SPSTSPDT (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 VOLTAGE 2. CARRY CURRENT SMALL WIRE + HIGH CURRENT STRANDEDSOLID FlexibleHigher current TypeGaugeMax INotes Wrap wire30200 mAwrapping, signal level only Hookup24/221-2 Ageneral purpose Lamp cord185 A House wire14/1215/20 A “CABLE” = multiconductor wire bundle e.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 – mA (can deliver 12 mA for 48 hrs) Discharge curve t 9V Alkaline technology See (or other sites) for more mA Hrs Service life

Battery technologies