REFERENCE
Data 367
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Reactance
LM386 Audio Power Amplifier IC
Capacitors and inductors have the property known as reactance which is the property that opposes any change in the current flow. It therefore most commonly applies to AC. Inductive reactance increases with frequency and capacitive reactance decreases with frequency. When
reactance is combined with resistance a new property known as impedance is formed, which is
similar to DC resistance, except it has an associate phase angle, due to its reactive component.
22µF
+
2
Vin
XL = 2.π.ƒ.L
Capacitive reactance is calculated as follows:-
1
XC
=
—
2.π.ƒ.C
The formula below will calculate the total impedance of a resistor in series with a
reactive component. As follows:-
Z = √X2+R2
Where:
XC = Capacitive impedance in ohms
1
-
8
4
4.7kΩ
Inductive reactance is calculated as follows :-
R1
0.47µF
470µF / 16V
5
LM386
3
10kΩ
7
+
10Ω
R2
6
XL = Inductive impedance in ohms
C = Capacitance in farads
L = Inductance in henries
ƒ = Frequency in hertz
0.1µF
0.01µF
Vs
Where:
Z = Complex impedance in ohms
X = Reactance
R = Resistance of the series resistor
Output Power (mW)
LM386
Load Resistor R2
Gain
The LM386 Audio Power Amplifier
has a gain which may be set from
20 to 200, and can drive loads between 4 and 16 ohms. It's a very
useful low voltage audio amplifier IC.
R1
Vs
4Ω
8Ω
16Ω
20
∞
5V
190
160
90
50
680
6V
250
250
150
100
180
9V
380
560
400
200
0
12V
380
660
780
RMS Voltage Equivalents
For a given AC voltage, the RMS equivalent will be the same as the DC voltage that gives the
same heating effect as the AC voltage in question. Take note that the quantity Vp is the value from
the zero crossing of the waveform to the peak, not from the neg. peak to the pos. peak.
LM1875 20W Audio Power Amplifier IC
C1
2.2µF
+Vcc
1
Vin
VRMS (Sine) = VP / √2 = VP x 0.707
VRMS (Triangle) = VP x 0.577
R1
1M
+
C3 0.1µF
5
R2
22kΩ
LM1875
2
3
-
4
R5
1Ω
-Vee
C4
0.1µF
The RMS value of a square waveform is equal to its peak value, as the magnitude of a square
wave remains constant over the half-period. (Assuming a 50% duty cycle).
4Ω or
8Ω
C5
0.22µF
R4 20kΩ
R3 1kΩ
C2 22µF
PCB Track Widths
When designing PCBs it is imperative that you design with current handling in mind. The following
table allows you to design appropriate track widths to supply adequate current to components without
significant temperature rise. For a 10° C temperature rise, minimum track widths are:
Width (inches)
0.008”
0.012”
0.020”
0.050”
0.100”
0.200”
0.325”
Width (mm)
0.20
0.30
0.50
1.27
2.54
5.08
8.25
±30V max.
100mA max.
0.015%
90dB
4A
Atmel® atMega328p Pinout
Ground
Control
1
28
PC5 PCINT13
ADC5
A5
SCL
RXD
PCINT16 PD0
2
27
PC4 PCINT12
ADC4
A4
SDA
1
TXD
PCINT17 PD1
3
26
PC3 PCINT11
ADC3
A3
OC2B
Optocouplers
4
25
PC2 PCINT10
ADC2
A2
PCINT19 PD3
5
24
PC1
PCINT9
ADC1
A1
T0
4
XCK
23
PC0
PCINT8
ADC0
A0
PCINT20 PD4
6
Atmega328 Pin
VCC
7
Digital Pin
GND
8
22
GND
21
AREF
Analog Related Pin
OSC1 XTAL1
PCINT6
PB6
9
PWM Pin
OSC2 XTAL2
PCINT7
PB7
10
19
PB5
PCINT5
20
VCC
SCK
13
Serial Pin
OC0B
PWM
5
T1
PCINT21 PD5
11
18
PB4
PCINT4
MISO
12
Arduino Pin
OC0A
PWM
6
AIN0
PCINT22 PD6
12
17
PB3
PCINT3
OC2A
11
PWM MOSI
7
AIN1
PCINT23 PD7
13
16
PB2
PCINT2
OC1B
10
PWM
8
CLKO
PCINT0
14
15
PB1
PCINT1
OC1A
9
PWM
GPIO02
Arduino Pin refers to the pin number
printed on the UNO R3 board.
ICP1
PB0
SS
For more information, visit www.arduino.cc or www.atmel.com
1
2
Ground
3V3
4
GPIO14
DC Power
3
6
SDA1 I2C
5
GPIO15
SCL I2C
8
5V
DC Power
5V
DC Power
TXD0
RXD0
7
GPIO18
GPIO04
10
GPIO_GCLK
9
Ground
GPIO_GEN1
Ground
11 12
GPIO23
GPIO_GEN4
GPIO24
GPIO_GEN5
Ground
GPIO25
GPIO_GEN6
GPIO08
SPI_CE0_N
GPIO07
SPI_CE1_N
GPIO17
GPIO_GEN0
GPIO27
15 16
17 18
19 20
21 22
23 24
ID_SC
13 14
GPIO_GEN2
GPIO22
GPIO_GEN3
3V3
DC Power
GPIO10
SPI_MOSI
GPIO09
SPI_MISO
GPIO11
SPI_CLK
Ground
Ground
I2C ID EEPROM
GPIO12
25 26
29 30
Ground
27 28
GPIO05
31 32
GPIO16
ID_SD
GPIO06
33 34
I2C ID EEPROM
GPIO13
GPIO20
5V
35 36
Optocouplers are used where electrical isolation is required. An LED and photodiode link is used
to provide isolation. This circuit can be used to interface a 5V switching source which needs to be
isolated from another unit. It has been configured for 12V output which can be directly interfaced
to other components.
GPIO19
4
GPIO21
3
Raspberry Pi 2 Model B GPIO Header Pinout
37 38
5
GPIO26
6
2
39 40
1
DC OPTOCOUPLERS
12V
1kΩ
Signal In
PCINT18 PD2
INT1
Ground
300mW
7500V Peak
400V LED
15mA LED
1.5
INT0
3
GPIO03
AC OPTOCOUPLERS
TRIAC Driver MOC3021 and MOC3041
The MOC3041 is identical to the MOC3021 except that it triggers at the
zero crossing point. This will only let full half wave cycles pass, thus
giving a smoother turn ON curve. This means that it will not work as a
wave chopper eg. when used in dimming a light by delaying the turn on
time.
2
PWM
atmega328p
Power
Specifications Z 1645 (4N28):
Diode Vr:
3V
If:
80mA cont, 3A peak
Vf @ 50mA:
1.5mA
Pd:
150mW
NPN Vce:
30V
Vcb
70V
Pd:
150mW
Ice-Dark Current: (Vce 10V)
50nA Max
Total Device rating Pd:
250mW
Isolation Voltage:
500V Min
PC6
0
Reset PCINT14
Legend
Port Pin
Specifications Z 1642 & Z 1644:
Package Dissipation:
Surge Isolation Voltage:
Blocking Voltage:
Trigger Current:
Forward Voltage (Max):
5
4
3
2
1
Current
0.5A
0.75A
1.25A
2.5A
4.0A
7.0A
10.0A
Supply Voltage:
Supply Current:
THD at 20W @ 1kHz:
Open Loop Gain:
Current Limit:
For more information, visit www.raspberrypi.org
4.7kΩ
1
6
2
5
3
4
Signal Out
Optocoupler
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