Transcript Document

Basic Electronics
How do I hook up a ________
to my ________circuit?
I
R
+
V
-
Electricity in a circuit
• Potential
Volts [ V ]
• Current
Amps [ A ]
• Resistance
Ohms [ Ω ]
• Power
Watts [ W ]
I
R
+
V
Image: http://www.productionapprentice.com/
Electricity in a circuit
• Potential
Volts [ V ]
Fluid flow through pipe
• “pressure”
• Current
Amps [ A ]
• “rate of flow”
• Resistance
Ohms [ Ω ]
• “pipe length or
diameter”
• Power
Watts [ W ]
• rate of energy
Combining Stuff
Series R (adds)
Parallel R (decreases)
Rtotal = R1 + R2 + R3
Rtotal =
1 / [1/R1 + 1/R2 + 1/R3]
A
B
Kirchoff’s Current Law:
I out = I in
Node A: i2 = i3
Node B: I = I1 +I2 +I3
OHM'S LAW
V=I * R
I
volts = amps * ohms
volts = mA * Kohms
+
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 Answer underneath
I = V/R = 9V/1K = 9mA = .009A
resistor
I
1/R
V
Diodes
P-N Junction
V-I Curve
If |ID| > Imax
“I’m on fire”
• “One-way” Valve: only allows current flow in one
direction
• Vdiode  0.6v (when “on”)
Using Diodes
• Limit Current (I < Imax)
• Vdiode ~ 0.6v
Choose R >>
(5v - .6)/ Imax
R=?
(VR = 5v-0.6v
(V0.6v)
R= 4.4v/ 20mA
= 220 Ohms
OK
NO!
How do I hook up an _LED_
to my Arduino circuit?
Which of These Work?
0
NOPE:
330
10K
OK
NOPE:
Answer underneath
Not Enough
Current
330
NOPE:
LED
Backwards
LED Facts
On fire
• 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
I
ON
OFF
happy
Von
1.5 V
V
Other Colors:
LED
anode
Wants ~10 mA
I
cathode
+ 1.5 V -
I = ??
Other Colors:
V
5  1 .5
I 

 10 . 6 mA
Answer
underneath
R
330
10-20mA or More
ARDUINO CONTROL OF LED
ARDUINO
Crucial
5V
0V
PIN 0
20 mA max
GND
digitalWrite(0,HIGH); // applies 5V to pin 0
delay(1000);
// waits a second
digitalWrite(0,LOW); // applies 0V to pin 0
LED’s off a battery?
Wants ~10 mA
anode
I
cathode
+ 1.5 V Vbattery
R
VR=Vbatt-Vcolor
Vcolor=?
Idesired=?
Vbatt
R = ??
Other Colors:
3.3v
R10mA= 160
5v
9v
12v
330
730
1K
Answer
underneath
R = (Vbatt
– Vcolor)/Idesired
10-20mA or More
Light 3 LEDs via 1 Pin
ARDUINO
5V
Need 30 to 60 mA & 3 Resistors
0V
PIN 0
20 mA max
GND
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
ARDUINO
5V, 20 mA
PIN 0
DEVICE
GND
What if device needs more than 5V or
more than 20 mA??
…Need Arduino-actuated Switch
Computer controlled switch
V big
DEVICE
ARDUINO
PIN 0
GND
I big
Arduino 
I
ON
OFF
V
LOAD: MOTOR, SOLENOID, RELAY, LAMP, …
Transistor
current-controlled amplifier, current-controlled switch
BASE
COLLECTOR
I small
I big = b*I small
EMITTER
Think: spray can!
COLLECTOR
BASE
EMITTER
Ic = b*Ib
Ib
Ie = Ib + Ic
ONE-WAY!
Arduino
5V
Arduino 
0V
+
Vbe  0.6v
-
ON
I
ON
I
OFF
V
OFF
Vce sat
0.1 – 2.0 V
V
LOAD: MOTOR, SOLENOID, RELAY, LAMP, …
(BJT) Transistors
V-I CurveIf |Ice| > Imax
N-P-N Junction
“I’m on fire”
ON
I
Ib
OFF
Vce sat
0.1 – 2.0 V
• “One-way” Amplifier
• Can use as an on-off switch
V
Inside (BJT) Transistors
Ic = b*Ib
N-P-N
Junction
Ib
Ie = Ib + Ic
Vbe
 0.6v
Vce 
0.6v to 2v
(see datasheet)
• 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
How do I hook up a _____* to
my Arduino circuit?
*Anything other than an LED
Transistors Require a Resistor
Ib = (5-.6)V /1K
= 4mA
Ib = (5-.6)V/ 0 
=A
5V
0V
Vbe=
0.6v
OK
“I’m on fire”
NO!
Which Transistor?
TO-92
TO-220
2N3904
TIP120
100 mA
1-2 A
TO-3
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
-
+
Arduino pin limits
20 mA per PIN
40 mA TOTAL
10.6 mA
4.4 mA
1A
POWER
+
V
I
P=V*I
-
P = ??
I = V/R = 9/10 = 0.9 A
Answer underneath
P = V*I = 9*.9 = 8.1 W
I
P = 12 * I
HEAT
I, V
t, w
WOW! WHAT A
GREAT MOTOR I
GOT AT AX-MAN!
AND IT RUNS ON
12v!
Later…
YOUCH!!
IT'S HOT!
12
V
ib 
5 .0  0 .6
 4 . 4 mA
1000
5V
Ic
Ib
Vce sat ~ 2.0 V
Let Ic = 5 A
HOT
PWR = V*I = 2.0*5 = 10 W !!!
wasted
5V
0V
ON
I
ON
I
OFF
V
OFF
Vce sat
0.1 – 2.0 V
V
LOAD: MOTOR, SOLENOID, RELAY, LAMP, …
RELAYS
To control larger loads
Relays
• Electromagnet-controlled switch
• User for (1) larger loads, (2) bi-directional motor
COIL
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
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 174431
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
Force when
energized
MAX ON-TIME = ½ SEC
¼ in.
x
www.jameco.com
SPST
(NO, NC)
Switches
SPDT
#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
STRANDED
Flexible
SMALL WIRE
+
HIGH CURRENT
SOLID
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
5A
House wire
14/12
15/20 A
“CABLE” = multiconductor wire bundle
e.g. modular phone cord: 28g solid, 4 conductor
BATTERIES
• Primary
• Important specs
– Zinc
– Energy density
– Alkaline (most
– Voltage
common)
• Zinc/Alkaline: 1.5 V
– Lithium (camera,
• Lead Acid: 2.0 V
watch)
– cars: 6, 12 V
• Secondary
• NiCd: 1.2 V
(rechargeable)
– Power tools: 4.8, 6.0,
– Sealed lead acid (car)
7.2, 9.6, 12, 18 V
– Gel
– Maximum current
– NiCd
• “Cold-cranking amps”
– NiMH
– Capacity
– Lithium
• 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)
100
Service life
Hrs
1
10
mA
100
Alkaline technology
9V
Discharge curve
t
See www.duracell.com (or other sites) for more
Battery technologies
Chemistry
NiCd
Energy density Cell voltage
(W-H/Kg)
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