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Energy from the road
side
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To feed in electric energy the signalization of Highways one produces
electricity with wind but it's the wind produce by the displacement of
cars and trucks, for example a small truck at 70 mph produces a
speed wind of 30 mph. To exploit this kind of wind one must a vertical
axis wind turbine near the road, the natural wind give energy too. The
idea is: Have an self energy-feed unit for all signalization system of
highway, to save energy and money
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In this project we show that how we generate a valuable voltage with the
help of moving traffic on the road. In this project we use conversion of
mechanical energy into electrical energy. For this purpose we install one
vertical axix wind mill on the road. On all the wind mill we use dynamo
to generate a voltage. When wind rotate then dynamo also rotate and
generate the voltage With the help of this dynamo we convert the
mechanical energy into electrical energy. We use dc dynamo, so output from
the dynamo is connected to the dc battery. When battery is fully charged
then we use battery for our project.
We install one photoelectric effect in the project. Street light is to be switch
on automatically in the night and lights are automatically off in the day
night.
In this project we switch on the street light in night in half mode. Half mode
means all the lights are to be on in 50 percent on/off mode. Rest of lights are
to be on if the traffic is on the road. If the road is with traffic then all the
lights are on. If the road is without traffic then 50 percent lights are again
off.
For road sensing, we use two pair of infra red sensor on the road. When any
car cross the road then infra red beam is interrupted and signal is connected
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to the controller. Controller sense the signal and increment the counter.
Counter display the total number of vehicle on road. When counter shows a
0 number then road lights are off to 50 percent.
In circuit we use LDR as a light dependent resistor to sense the darkness.
When LDR is in dark then LDR offer a low resistance. At this time LDR
gives a signal to the circuit to switch on/off the road light for 50 percent. As
the LDR is in dark then 50 percent is on. But if the traffic is on the road
then road sensor gets a signal and connect to the circuit. In the road sensor
we use infra red l.e.d and photodiode as a road sensor. When any vehicle
interrupt the infra red light then circuit sense the interruption and at this
time Or comparator circuit switch on the light. In this project we use LM
358 as a comparator with infra red sensors.
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To feed in electric energy the signalization of Highways one produces
electricity with wind but it's the wind produce by the displacement of
cars and trucks, for example a small truck at 70 mph produces a
speed wind of 30 mph. To exploit this kind of wind one must a vertical
axis wind turbine near the road, the natural wind give energy too. The
idea is: Have an self energy-feed unit for all signalization system of
highway, to save energy and money
In the night lights are automatic on with the help of photovoltaic switch
logic.
But all lights are not on, only half light are on. Other half lights switch on
automatically when any vehicle move on the bridge, when there is no
vehicle on the bridge then lights are off automatically.
We use two infra red sensors to check the movement of vehicle. When first
infra red sensor is on then lights are on and when second sensor is interrupt
then lights are off.
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COMPONENTS USED:
89S51 MICROCONTROLLER.
PHOTODIODE( 2)5MM
INFRA RED LED (2) 5MM
7805 REGULATOR ( 5 VOLT)
CRYSTAL ( 12 MHZ) CONNECTED TO PIN NO 18 AND 19
27 PF ( 2_) GROUNDED FROM CRYSTAL
RESISTANCE:
10K OHM (3)
470 OHM(2)
270 OHM (6)
1 K OHM (1)
LDR FOR AUTOMATIC STREET LIGHT
NPN BC 548 FOR LDR SWITCHING
GENERAL PURPOSE PCB
12 VOLT DYANMO
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6 VOLT CHARGEBALE BATTERY
CHANGOVER SWITCH
L.E.D ( 6 ) FOR STREET LIGHT
MAIN THEME OF THIS PROJECT
NON CONVENTIONAL ENERGY GENERATION
CONCEPT:
MECHANICAL TO ELECTRICAL ENERGY
LOGIC: USE DYANMO AS A SPEED BRAKER , One rod with the
dynamo is placed like a speed braker. Dyanmo is so powerful. Movement of
vehicle just rotate the dynamo shaft and electricity is generated. This
voltage is to be stored in the chargeable battery.
In the night lights are automatic on with the help of photovoltaic switch
logic.
But all lights are not on, only half light are on. Other half lights switch on
automatically when any vehicle move on the bridge, when there is no
vehicle on the bridge then lights are off automatically.
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In this project we use 89s51 controller , family member of the 8051 family..
supply voltage of the microcontroller is 5 volt dc . for this prupose we
convert the battery voltage into 5 volt dc with the help of the 5 volt regulator
circuit. For this purpose we use ic 7805 regulator to regulate the high
voltage inot 5 volt dc. One capacitor is ground from the regulator for
filteration . Capcitor reduce the noise . Output of the regulator is connected
to the pin no 40 of the controller directly. One crystal is connected to the pin
no 18 and 19 of the controller to provide a oscillation signal. For this
purpose we use 12 Mhz crystal. Two capacitor are grounded from the crystal
to reduce the noise In this project we use two logic. One is light sensitive
logic and second is road sensor logic. When sensor is in dark then all the
lights are on and when sensor is in light then all the lights are off. This is
done by the light sensor ( LDR). LDR is a light dependent resistor , when
light fall on the ldr then ldr offers a low resistance and when ldr is in dark
then ldr offeres a high resistance. Here in this project we use the ldr with npn
transistor circuit. Emitter of the npn transistor is connected to the ground
and collector is connected to the pin no 3 of the controller.
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when ldr is in light then there is low positive on the base of the npn
transistor and collector is become more negative. When ldr is in dark then
there is no base voltage and hence collector become more positive.
Microcontroler sense this change of voltage and switch on the output led
whish is connected to the port 0,
Out put leds are connected with the port 0 through the resistance in series,
here in this we use 6 l.e.d . Common point of the l.e.d is connected with the
positive line. Out of 6 only three l.e.ds are on .
Our second part of this project is infra red sensor. In this logic when any car
cross the first ir sensor then all the led are on and if the traffic continuous
then led are on if the no car on the road then again three led are eon and
three are off
For this purpose we use two IR sensor circuit with this project.
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here in this project we use infra red sensor and one photodiode circuit when
light fall on the photosensor then resistance of photos sensor become low
and hence negative voltage is applied to the controller, when any car cross
the photodiode and then photo diode resistance become high and hence
signal is change on the pin no 2 of the controller. As the controller sense
this change of signal on pin then all the light are on .
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Main program is written in the 8051 ide siftware. We wrote the software in
the assembly language. In the 8051 ide software
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Once the software is complete and there is no error then we transfer this
hex code into the blank ic with the help of the serial port programmer circuit.
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Basic of the microcontroller.
PROJECT DESCRIPTION
MICROCONTROLLER AT89C51
Architecture of 8051 family:-
The figure 1 above shows the basic architecture of 8051 family of
microcontroller.
Features Compatible with MCS-51 Products
4K Bytes of In-System Reprogrammable Flash Memory
Endurance: 1,000 Write/Erase Cycles
Fully Static Operation: 0 Hz to 24 MHz
Three-Level Program Memory Lock
128 x 8-Bit Internal RAM
32 Programmable I/O Lines
Two 16-Bit Timer/Counters
Six Interrupt Sources
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Programmable Serial Channel
Low Power Idle and Power Down Modes
Description
The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K
bytes of Flash Programmable and Erasable Read Only Memory (PEROM). The device is
manufactured using Atmels high density nonvolatile memory technology and is
compatible with the industry standard MCS-51 instruction set and pinout. The on-chip
Flash allows the program memory to be reprogrammed in-system or by a conventional
nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a
monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a
highly flexible and cost effective solution to many embedded control applications. The
AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM,
32 I/O lines, two 16-bit timer/counters, five vector two-level interrupt architecture, a full
duplex serial port, and on-chip oscillator and clock circuitry.
In addition, the AT89C51 is designed with static logic for operation down to zero
frequency and supports two software selectable power saving modes. The Idle Mode stops
the CPU while allowing the RAM, timer/counters, serial port and interrupt system to
continue functioning. The Power down Mode saves the RAM contents but freezes the
oscillator disabling all other chip functions until the next hardware reset.
Pin Description
VCC
Supply voltage.
GND
Ground.
Port 0
Port 0 is an 8-bit open drain bidirectional I/O port. As an output port each pin can sink
eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high
impedance inputs. Port 0 may also be configured to be the multiplexed low order
address/data bus during accesses to external program and data memory. In this mode P0
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has internal pull-ups. Port 0 also receives the code bytes during Flash programming, and
outputs the code bytes during program verification.
External pull-ups are required during program verification.
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Port 1
Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers can
sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the
internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being
pulled low will source current (IIL) because of the internal pull-ups. Port 1 also receives
the low-order address bytes during Flash programming and verification.
Port 2
Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers can
sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the
internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being
pulled low will source current (IIL) because of the internal pull-ups. Port 2 emits the high-
order address byte during fetches from external program memory and during accesses to
external data memory that uses 16-bit addresses (MOVX @ DPTR). In this application it
uses strong internal pull-ups when emitting 1s. During accesses to external data memory
that uses 8-bit addresses (MOVX @ RI); Port 2 emits the contents of the P2 Special
Function Register. Port 2 also receives the high-order address bits and some control signals
during Flash programming and verification.
Port 3
Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers can
sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the
internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being
pulled low will source current (IIL) because of the pull-ups. Port 3 also serves the functions
of various special features of the AT89C51 as listed below:
Port 3 also receives some control signals for Flash programming and verification.
RST
Reset input. A high on this pin for two machine cycles while the oscillator is running resets
the device.
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ALE/PROG
Address Latch Enable output pulse for latching the low byte of the address during accesses
to external memory. This pin is also the program pulse input (PROG) during Flash
programming. In normal operation ALE is emitted at a constant rate of 1/6 the oscillator
frequency, and may be used for external timing or clocking purposes. Note, however, that
one ALE pulse is skipped during each access to external Data Memory. If desired, ALE
operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is
active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled
high. Setting the ALE-disable bit has no effect if the microcontroller is in external
execution mode.
PSEN
Program Store Enable is the read strobe to external program memory.
Port Pin Alternate Functions
P3.0 RXD (serial input port)
P3.1 TXD (serial output port)
P3.2 INT0 (external interrupt 0)
P3.3 INT1 (external interrupt 1)
P3.4 T0 (timer 0 external input)
P3.5 T1 (timer 1 external input)
P3.6 WR (external data memory write strobe)
P3.7 RD (external data memory read strobe)
When the AT89C51 is executing code from external program memory, PSEN is activated
twice each machine cycle, except that two PSEN activations are skipped during each access
to external data memory.
EA/VPP
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External Access Enable. EA must be strapped to GND in order to enable the device to fetch
code from external program memory locations starting at 0000H up to FFFFH. Note,
however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA
should be strapped to VCC for internal program executions. This pin also receives the 12-
volt programming enable voltage (VPP) during Flash programming, for parts that require
12-volt VPP.
XTAL1
Input to the inverting oscillator amplifier and input to the internal clock operating circuit.
XTAL2
Output from the inverting oscillator amplifier.
Oscillator Characteristics
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which
can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz
crystal or ceramic resonator may be used. To drive the device from an external clock
source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure
2.There are no requirements on the duty cycle of the external clock signal, since the input
to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and
maximum voltage high and low time specifications must be observed.
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Idle Mode
In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain active.
The mode is invoked by software. The content of the on-chip RAM and all the special
functions registers remain unchanged during this mode. The idle mode can be terminated
by any enabled
Interrupt or by hardware reset. It should be noted that when idle is terminated by a hard
Hardware reset, the device normally resumes program execution, from where it left off, up
to two machine cycles before the internal reset algorithm takes control. On-chip hardware
inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To
eliminate the possibility of an unexpected write to a port pin when Idle is terminated by
reset, the instruction following the one that invokes Idle should not be one that writes to a
port pin or to external memory.
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Status of External Pins during Idle and Power down Modes
Mode Program Memory ALE PSEN PORT0 PORT1 PORT2 PORT3
Idle Internal 1 Data
Idle External 1 Float Data Address Data
Power down Internal 0 Data
Power down External 0 Float Data
Power down Mode
In the power down mode the oscillator is stopped, and the instruction that invokes power
down is the last instruction executed. The on-chip RAM and Special Function Registers
retain their values until the power down mode is terminated. The only exit from power
down is a hardware reset. Reset redefines the SFRs but does not change the on-chip RAM.
The reset should not be activated before VCC is restored to its normal operating level and
must be held active long enough to allow the oscillator to restart and stabilize.
Program Memory Lock Bits
On the chip are three lock bits which can be left un-programmed (U) or can be
programmed (P) to obtain the additional features listed in the table below:
When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during
reset. If the device is powered up without a reset, the latch initializes to a random value,
and holds that value until reset is activated. It is necessary that the latched value of EA be
in agreement with
The current logic level at that pin in order for the device to function properly.
Lock Bit Protection Modes
Program Lock Bits Protection Type
LB1 LB2 LB3
1 U No program lock features.
2 P U MOVC instructions executed from external program memory are disabled from
fetching code
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Bytes from internal memory, EA is sampled and latched on reset, and further programming
of the
Flash is disabled.
3 P U Same as mode 2, also verify is disabled.
4 P same as mode 3, also external execution is disabled.
Programming the Flash
The AT89C51 is normally shipped with the on-chip Flash memory array in the erased state
(that is, contents = FFH) and ready to be programmed. The programming interface accepts
either a high-voltage (12-volt) or a low-voltage (VCC) program enable signal. The low
voltage programming mode provides a convenient way to program the AT89C51 inside the
users system, while the high-voltage programming mode is compatible with conventional
third party Flash or EPROM programmers. The AT89C51 is shipped with either the high-
voltage or low-voltage programming mode enabled. The respective top-side marking and
device signature codes are listed in the following table. The AT89C51 code memory array
is programmed byte-by byte
In either programming mode. To program any nonblank byte in the on-chip Flash Memory,
the entire memory must be erased using the Chip Erase Mode.
Programming Algorithm:
Before programming the AT89C51, the address, data and control signals should be set up
according to the Flash programming mode table and Figures 3 and 4. To program the
AT89C51, take the following steps.
1. Input the desired memory location on the address lines.
2. Input the appropriate data byte on the data lines.
3. Activate the correct combination of control signals.
4. Raise EA/VPP to 12V for the high-voltage programming mode.
5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-
write cycle is self-timed and typically takes no more than 1.5 ms. Repeat steps 1 through 5,
changing the address and data for the entire array or until the end of the object file is
reached.
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Data Polling:
The AT89C51 features Data Polling to indicate the end of a write cycle. During a write
cycle, an attempted read of the last byte written will result in the complement of the written
datum on PO.7. Once the write cycle has been completed, true data are valid on all outputs,
and the next cycle may begin. Data Polling may begin any time after a write cycle has been
initiated.
Ready/Busy:
The progress of byte programming can also be monitored by the RDY/BSY output signal.
P3.4 is pulled low after ALE goes high during programming to indicate BUSY. P3.4 is
pulled high again when programming is done to indicate READY.
Program Verify:
If lock bits LB1 and LB2 have not been programmed, the programmed code data can be
read back via the address and data lines for verification. The lock bits cannot be verified
directly. Verification of the lock bits is achieved by observing that their features are
enabled.
Chip Erase:
The entire Flash array is erased electrically by using the proper combination of control
signals and by holding ALE/PROG low for 10 ms. The code array is written with all 1s.
The chip erase operation must be executed before the code memory can be re-programmed.
Reading the Signature Bytes:
The signature bytes are read by the same procedure as a normal verification of locations
030H,
031H, and 032H, except that P3.6 and P3.7 must be pulled to a logic low. The values
returned are as follows.
(030H) = 1EH indicates manufactured by Atmel
(031H) = 51H indicates 89C51
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(032H) = FFH indicates 12V programming
(032H) = 05H indicates 5V programming
Programming Interface
Every code byte in the Flash array can be written and the entire array can be erased by
using the appropriate combination of control signals. The write operation cycle is self
timed and once initiated, will automatically time itself to completion. All major
programming vendors offer worldwide support for the Atmel microcontroller series. Please
contact your local programming vendor for the appropriate software revision.
Flash Programming Modes
Note: 1. Chip Erase requires a 10-ms PROG pulse.
SPECIAL FUNCTION REGISTER (SFR) ADDRESSES:
ACC ACCUMULATOR 0E0H
B B REGISTER 0F0H
PSW PROGRAM STATUS WORD 0D0H
SP STACK POINTER 81H
DPTR DATA POINTER 2 BYTESDPL LOW BYTE OF DPTR 82H
DPH HIGH BYTE OF DPTR 83H
P0 PORT0 80H
P1 PORT1 90H
P2 PORT2 0A0H
P3 PORT3 0B0H
TMOD TIMER/COUNTER MODE CONTROL 89H
TCON TIMER COUNTER CONTROL 88H
TH0 TIMER 0 HIGH BYTE 8CH
TLO TIMER 0 LOW BYTE 8AH
TH1 TIMER 1 HIGH BYTE 8DH
TL1 TIMER 1 LOW BYTE 8BH
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SCON SERIAL CONTROL 98H
SBUF SERIAL DATA BUFFER 99H
PCON POWER CONTROL 87H
TMOD (TIMER MODE) REGISTER
Both timers are the 89c51 share the one register TMOD. 4 LSB bit for the timer 0 and 4
MSB for the timer 1.In each case lower 2 bits set the mode of the timer
Upper two bits set the operations.
GATE: Gating control when set. Timer/counter is enabled only while the INTX pin
is high and the TRx control pin is set. When cleared, the timer is enabled whenever the
TRx control bit is set
C/T: Timer or counter selected cleared for timer operation (input from internal
system clock)
M1 Mode bit 1
M0 Mode bit 0
M1 M0 MODE OPERATING MODE
0 0 0 13 BIT TIMER/MODE
0 1 1 16 BIT TIMER MODE
1 0 2 8 BIT AUTO RELOAD
1 1 3 SPLIT TIMER MODE
PSW (PROGRAM STATUS WORD)
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CY PSW.7 CARRY FLAG
AC PSW.6 AUXILIARY CARRY
F0 PSW.5 AVAILABLE FOR THE USER FRO GENERAL PURPOSE
RS1 PSW.4 REGISTER BANK SELECTOR BIT 1
RS0 PSW.3 REGISTER BANK SELECTOR BIT 0
0V PSW.2 OVERFLOW FLAG
-- PSW.1 USER DEFINABLE BIT
P PSW.0 PARITY FLAG SET/CLEARED BY HARDWARE
PCON REGISATER (NON BIT ADDRESSABLE)
If the SMOD = 0 (DEFAULT ON RESET)
TH1 = CRYSTAL FREQUENCY
256---- ____________________
384 X BAUD RATE
If the SMOD IS = 1
CRYSTAL FREQUENCY
TH1 = 256--------------------------------------
192 X BAUD RATE
There are two ways to increase the baud rate of data transfer in the 8051
1. To use a higher frequency crystal
2. To change a bit in the PCON register
PCON register is an 8 bit register. Of the 8 bits, some are unused, and some are used for the
power control capability of the 8051. The bit which is used for the serial communication is
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D7, the SMOD bit. When the 8051 is powered up, D7 (SMOD BIT) OF PCON register is
zero. We can set it to high by software and thereby double the baud rate
BAUD RATE COMPARISION FOR SMOD = 0 AND SMOD =1
TH1 (DECIMAL) HEX SMOD =0 SMOD =1
-3 FD 9600 19200
-6 FA 4800 9600
-12 F4 2400 4800
-24 E8 1200 2400
XTAL = 11.0592 MHZ
IE (INTERRUPT ENABLE REGISTOR)
EA IE.7 Disable all interrupts if EA = 0, no interrupts is acknowledged
If EA is 1, each interrupt source is individually enabled or disabled
By sending or clearing its enable bit.
IE.6 NOT implemented
ET2 IE.5 enables or disables timer 2 overflag in 89c52 only
ES IE.4 Enables or disables all serial interrupt
ET1 IE.3 Enables or Disables timer 1 overflow interruptEX1 IE.2 Enables or disables external interrupt
ET0 IE.1 Enables or Disables timer 0 interrupt.
EX0 IE.0 Enables or Disables external interrupt 0
INTERRUPT PRIORITY REGISTER
If the bit is 0, the corresponding interrupt has a lower priority and if the bit is 1 thecorresponding interrupt has a higher priority
IP.7 NOT IMPLEMENTED, RESERVED FOR FUTURE USE.
IP.6 NOT IMPLEMENTED, RESERVED FOR FUTURE USE
PT2 IP.5 DEFINE THE TIMER 2 INTERRUPT PRIORITY LELVEL
PS IP.4 DEFINES THE SERIAL PORT INTERRUPT PRIORITY LEVEL
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PT1 IP.3 DEFINES THE TIMER 1 INTERRUPT PRIORITY LEVEL
PX1 IP.2 DEFINES EXTERNAL INTERRUPT 1 PRIORITY LEVEL
PT0 IP.1 DEFINES THE TIMER 0 INTERRUPT PRIORITY LEVEL
PX0 IP.0 DEFINES THE EXTERNAL INTERRUPT 0 PRIORITY LEVEL
SCON: SERIAL PORT CONTROL REGISTER, BIT ADDRESSABLE
SCON
SM0 : SCON.7 Serial Port mode specified
SM1 : SCON.6 Serial Port mode specifier
SM2 : SCON.5
REN : SCON.4 Set/cleared by the software to Enable/disable reception
TB8 : SCON.3 the 9th bit that will be transmitted in modes 2 and 3, Set/cleared
By software
RB8 : SCON.2 In modes 2 &3, is the 9th data bit that was received. In mode 1,
If SM2 = 0, RB8 is the stop bit that was received. In mode 0
RB8 is not usedT1 : SCON.1 Transmit interrupt flag. Set by hardware at the end of the 8th bit
Time in mode 0, or at the beginning of the stop bit in the other
Modes. Must be cleared by software
R1 SCON.0 Receive interrupt flag. Set by hardware at the end of the 8th bit
Time in mode 0, or halfway through the stop bit time in the other
Modes. Must be cleared by the software.
TCON TIMER COUNTER CONTROL REGISTER
This is a bit addressable
TF1 TCON.7 Timer 1 overflows flag. Set by hardware when the Timer/Counter 1
Overflows. Cleared by hardware as processor
TR1 TCON.6 Timer 1 run control bit. Set/cleared by software to turn Timer
Counter 1 On/off
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TF0 TCON.5 Timer 0 overflows flag. Set by hardware when the timer/counter 0
Overflows. Cleared by hardware as processor
TR0 TCON.4 Timer 0 run control bit. Set/cleared by software to turn timer
Counter 0 on/off.
IE1 TCON.3 External interrupt 1 edge flag
ITI TCON.2 Interrupt 1 type control bit
IE0 TCON.1 External interrupt 0 edge
IT0 TCON.0 Interrupt 0 type control bit.
TF 1T R1T F0T R0IE IITI I E 0IT 0
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Light dependent resistors or LDRs are often used in circuits where it is necessaryto detect the presence or the level of light. They can be described by a variety of
names from light dependent resistor, LDR, photoresistor, or even photo cell(photocell) or photoconductor.
Although other devices such as photodiodes or photo-transistor can also beused, LDRs are a particularly convenient electronics component to use. Theyprovide large change in resistance for changes in light level.
In view of their low cost, ease of manufacture, and ease of use LDRs have beenused in a variety of different applications. At one time LDRs were used inphotographic light meters, and even now they are still used in a variety ofapplications where it is necessary to detect light levels.
What is an LDR or light dependent resistor
A photoresistor or light dependent resistor is a component that is sensitive tolight. When light falls upon it then the resistance changes. Values of theresistance of the LDR may change over many orders of magnitude the value ofthe resistance falling as the level of light increases.
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It is not uncommon for the values of resistance of an LDR or photoresistor to beseveral megohms in darkness and then to fall to a few hundred ohms in brightlight. With such a wide variation in resistance, LDRs are easy to use and thereare many LDR circuits available.
LDRs are made from semiconductor materials to enable them to have their lightsensitive properties. Many materials can be used, but one popular material forthese photoresistors is cadmium sulphide (CdS).
How an LDR works
It is relatively easy to understand the basics of how an LDR works withoutdelving into complicated explanations. It is first necessary to understand that anelectrical current consists of the movement of electrons within a material. Goodconductors have a large number of free electrons that can drift in a given
direction under the action of a potential difference. Insulators with a highresistance have very few free electrons, and therefore it is hard to make the themmove and hence a current to flow.
An LDR or photoresistor is made any semiconductor material with a highresistance. It has a high resistance because there are very few electrons that arefree and able to move - the vast majority of the electrons are locked into thecrystal lattice and unable to move. Therefore in this state there is a high LDRresistance.
As light falls on the semiconductor, the light photons are absorbed by the
semiconductor lattice and some of their energy is transferred to the electrons.This gives some of them sufficient energy to break free from the crystal lattice sothat they can then conduct electricity. This results in a lowering of the resistanceof the semiconductor and hence the overall LDR resistance.
The process is progressive, and as more light shines on the LDR semiconductor,so more electrons are released to conduct electricity and the resistance fallsfurther.
LDR summary
LDRs are very useful components that can be used for a variety of light sensingapplications. As the LDR resistance varies over such a wide range, they areparticularly useful, and there are many LDR circuits available beyond any shownhere. In order to utilise these components, it is necessary to know something ofhow an LDR works, which has been explained above.
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Types of wind turbines
Wind farm in the Tehachapi Mountains, California.
Wind turbines can be separated into two general types based on the axis
about which the turbine rotates. Turbines that rotate around a horizontal axisare most common. Vertical axis turbines are less frequently used.
Wind turbines can also be classified by the location in which they are to be
used. Onshore, offshore, or even aerial wind turbines have unique design
characteristics which are explained in more detail in the section on Turbine
design and construction.
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Wind turbines may also be used in conjunction with a solar collectorto
extract the energy due to air heated by the Sun and rising through a large
vertical Solar updraft tower.
Horizontal axis
Horizontal Axis Wind Turbines (HAWT) have the main rotor shaft and
generator at the top of a tower, and must be pointed into the wind by some
means. Small turbines are pointed by a simple wind vane, while large
turbines generally use a wind sensor coupled with a servomotor. Most have a
gearbox too, which turns the slow rotation of the blades into a quicker
rotation that is more suitable for generating electricity.
Since a tower produces turbulence behind it, the turbine is usually pointed
upwind of the tower. Turbine blades are made stiff to prevent the blades
from being pushed into the tower by high winds. Additionally, the blades are
placed a considerable distance in front of the tower and are sometimes tilted
up a small amount.
Downwind machines have been built, despite the problem of turbulence,
because they don't need an additional mechanism for keeping them in line
with the wind, and because in high winds, the blades can be allowed to bend
which reduces their swept area and thus their wind resistance. Because
turbulence leads to fatigue failures and reliability is so important, most
HAWTs are upwind machines.
There are several types of HAWT:
WindmillsThese four- (or more) bladed squat structures, usually with wooden
shutters or fabric sails, were pointed into the wind manually or via a
tail-fan. These windmills, generally associated with the Netherlands,were historically used to grind grain or pump water from low-lying
land. They greatly accelerated shipbuilding in the Netherlands, and
were instrumental in keeping itspolders dry.
American-style farm windmills
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These windmills were used by American prairie farmers to generate
electricity and to pump water. They typically had many blades,
operated at tip speed ratios (defined below) not better than one, and
had good starting torque. Some had small direct-current generators
used to charge storage batteries, to provide a few lights, or to operate
a radio receiver. The rural electrification connected many farms to
centrally-generated power and replaced individual windmills as a
primary source of farm power in the 1950s. Such devices are still used
in locations where it is too costly to bring in commercial power.
Wind turbines nearAalborg, Denmark
Common modern wind turbinesUsually three-bladed, sometimes two-bladed or even one-bladed (and
counterbalanced), and pointed into the wind by computer-controlled
motors. The rugged three-bladed turbine type has been championed by
Danish turbine manufacturers. These have high tip speeds of up to 6x
wind speed, high efficiency, and low torque ripple which contributes
to good reliability. This is the type of turbine that is used
commercially to produce electricity. They are usually white in color.
Ducted rotorStill something of a research project, the ducted rotor consists of aturbine inside a duct which flares outwards at the back. They are also
referred as Diffuser-Augmented Wind Turbines (i.e. DAWT). The
main advantage of the ducted rotor is that it can operate in a wide
range of winds and generate a higher power per unit of rotor area.
Another advantage is that the generator operates at a high rotation
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rate, so it doesn't require a bulky gearbox, so the mechanical portion
can be smaller and lighter. A disadvantage is that (apart from the
gearbox) it is more complicated than the unducted rotor and the duct
is usually quite heavy, which puts an added load on the tower.
Co-axial, multi-rotor horizontal axis turbines
Two or more rotors may be mounted to the same driveshaft, with their
combined co-rotation together turning the same generator - fresh wind is
brought to each rotor by sufficient spacing between rotors combined with an
offset angle alpha from the wind direction. Wake vorticity is recovered as
the top of a wake hits the bottom of the next rotor. Power has been
multiplied several times using co-axial, multiple rotors in testing conductedby inventor and researcher Douglas Selsam, for the California Energy
Commission in 2004. The first commercially available co-axial multi-rotor
turbine is the patented dual-rotor American Twin Superturbine from Selsam
Innovations in California, with 2 propellers separated by 12 feet. It is the
most powerful 7-foot diameter turbine available, due to this extra rotor.
Counter-rotating horizontal axis turbines
Counter rotating turbines can be used to increase the rotation speed of the
electrical generator. As of 2005, no large practical counter-rotating HAWTsare commercially sold. When the counter rotating turbines are on the same
side of the tower, the blades in front are angled forwards slightly so as to
avoid hitting the rear ones. If the turbine blades are on opposite sides of the
tower, it is best that the blades at the back be smaller than the blades at the
front and set to stall at a higher wind speed. This allows the generator to
function at a wider wind speed range than a single-turbine generator for a
given tower. To reduce sympathetic vibrations, the two turbines should turn
at speeds with few common multiples, for example 7:3 speed ratio. Overall,
this is a more complicated design than the single-turbine wind generator, butit taps more of the wind's energy at a wider range of wind speeds.
Appa designed and demonstrated a contra rotor wind turbine in FY 2000-
2002 funded by California Energy Commission. This study showed 30 to
40% more power extraction than a comparable single rotor system. Further it
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was observed that the slower the rotor speed better the performance.
Consequently Megawatt machines benefit most.
Cyclic stresses and vibration
Cyclic stresses fatigue the blade, axle andbearing material, and were a
major cause of turbine failure for many years. Because wind velocity
increases at higher altitudes, the backward force and torque on a horizontal
axis wind turbine (HAWT) blade peaks as it turns through the highest point
in its circle. The tower hinders the airflow at the lowest point in the circle,which produces a local dip in force and torque. These effects produce a
cyclic twist on the main bearings of a HAWT. The combined twist is worst
in machines with an even number of blades, where one is straight up when
another is straight down. To improve reliability, teetering hubs have been
used which allow the main shaft to rock through a few degrees, so that the
main bearings do not have to resist the torque peaks.
When the turbine turns to face the wind, the rotating blades act like a
gyroscope. As it pivots, gyroscopic precession tries to twist the turbine into aforward or backward somersault. For each blade on a wind generator's
turbine, precessive force is at a minimum when the blade is horizontal and at
a maximum when the blade is vertical. This cyclic twisting can quickly
fatigue and crack the blade roots, hub and axle of the turbine.
Vertical axis
Vertical Axis Wind Turbines (or VAWTs) have the main rotor shaft running
vertically. The advantages of this arrangement are that the generator and/or
gearbox can be placed at the bottom, near the ground, so the tower doesn'tneed to support it, and that the turbine doesn't need to be pointed into the
wind. Drawbacks are usually the pulsating torque produced during each
revolution, and the difficulty of mounting vertical axis turbines on towers,
meaning they must operate in the slower, more turbulent air flow near the
ground, with lower energy extraction efficiency.
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H-Darrieus-turbine
Darrieus wind turbineThese are the "eggbeater" turbines. They have good efficiency, but
produce large torque ripple and cyclic stress on the tower, which
contributes to poor reliability. Also, they generally require some
external power source, or an additional Savonius rotor, to start
turning, because the starting torque is very low. The torque ripple is
reduced by using 3 or more blades.
Giromill is a type of Darrieus
These lift-type devices have vertical blades. The cycloturbine varietyhas variable pitch, to reduce the torque pulsation and self-start . The
advantages of variable pitch are high starting torque, a wide, relatively
flat torque curve, a lower blade speed ratio, a higher coefficient of
performance, more efficient operation in turbulent winds, and a lower
blade speed ratio which lowers blade bending stresses. Straight, V, or
curved blades may be used.
Savonius wind turbineThese are the familiar two- (or more) scoop drag-type devices used in anemometers
and in the Flettner vents commonly seen on bus and van roofs, and some high-reliability low-efficiency power turbines. They always self-start (if at least three
scoops). They can sometimes have long helical scoops, to give smooth torque. The
Banesh rotor and especially the Rahai rotor improve efficiency by shaping theblades to produce significant lift as well as drag.
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Tower height
The wind blows faster at higher altitudes because of the drag of the surface(sea or land) and the viscosity of the air. The variation in velocity with
altitude, called wind shear, is most dramatic near the surface.
Wind turbines of varied height generating electricity in California.
Typically, in daytime the variation follows the 1/7th power law, which
predicts that wind speed rises proportionally to the seventh root of altitude.
Doubling the altitude of a turbine, then, increases the expected wind speeds
by 10% and the expected power by 34%. Doubling the tower height
generally requires doubling the diameter as well, increasing the amount of
material by a factor of eight.
In night time, or better: when the atmosphere becomes stable, wind speed
close to the ground usually subsides whereas at turbine hub altitude it does
not decrease that much or may even increase. As a result the wind speed is
higher and a turbine will produce more power than expected from the 1/7th
power law: doubling the altitude may increase wind speed by 20% to 60%.
A stable atmosphere is caused by radiative cooling of the surface and is
common in a temperate climate: it usually occurs when there is a (partly)
clear sky at night. When the (high altitude) wind is strong (10 meter wind
speed higher than approximately 6 to 7 m/s) the stable atmosphere isdisrupted because of friction turbulence and the atmosphere will turn
neutral. A daytime atmosphere is either neutral (no net radiation; usually
with strong winds and/or heavy clouding) orunstable (rising air because of
ground heating by the sun). Here again the 1/7th power law applies or is
at least a good approximation of the wind profile.
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For HAWTs, tower heights approximately twice to triple the blade length
have been found to balance material costs of the tower against better
utilisation of the more expensive active components.
Number of blades
For small (novelty or urban) HAWT turbines manufacturers typically shipthree-bladed turbines with three separate blades that must be assembled
onsite, into a central hub. Without careful assembly ensuring accurate
dynamic balance of the blades, the turbine can shake itself apart.
Most wind turbines have three blades. Very small turbines may use two
blades for ease of construction and installation. Vibration intensity decreases
with larger numbers of blades. Noise and wear are generally lower, and
efficiency higher, with three instead of two blades.
Turbines with larger numbers of smaller blades operate at a lowerReynoldsnumberand so are less efficient. Small turbines with 4 or more blades suffer
further losses as each blade operates partly in the wake of the other blades.
Also, the cost of the turbine usually increases with the number of blades.
Rotation controlTip speed ratio
The ratio between the speed of the wind and the speed of the tips of
the blades of a wind turbine. High efficiency 3-blade-turbines have tip
speed ratios of 6-7.
Modern wind turbines are designed to spin at varying speeds (a consequence
of their generator design, see below). Use of aluminum and composites in
their blades has contributed to low rotational inertia, which means that
newer wind turbines can accelerate quickly if the winds pick up, keeping the
tip speed ratio more nearly constant. Operating closer to their optimal tip
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speed ratio during energetic gusts of wind allows wind turbines to improve
energy capture from sudden gusts that are typical in urban settings.
In contrast, older style wind turbines were designed with heavier steel
blades, which have higher inertia, and rotated at speeds governed by the AC
frequency of the power lines. The high inertia buffered the changes in
rotation speed and thus made power output more stable.
The speed and torque at which a wind turbine rotates must be controlled for
several reasons:
To optimize the aerodynamic efficiency of the rotor in light winds.
To keep the generator within its speed and torque limits.
To keep the rotor and hub within their centripetal force limits. The
centripetal force from the spinning rotors increases as the square of
the rotation speed, which makes this structure sensitive to overspeed.
To keep the rotor and tower within their strength limits. Because the
power of the wind increases as the cube of the wind speed, turbines
have to be built to survive much higher wind loads (such as gusts of
wind) than those from which they can practically generate power.
Since the blades generate more downwind force (and thus put far
greater stress on the tower) when they are producing torque, mostwind turbines have ways of reducing torque in high winds.
To enable maintenance; because it is dangerous to have people
working on a wind turbine while it is active, it is sometimes necessary
to bring a turbine to a full stop.
To reduce noise; As a rule of thumb, the noise from a wind turbine
increases with the fifth power of the relative wind speed (as seen from
the moving tip of the blades). In noise-sensitive environments, the tip
speed can be limited to approximately 60 m/s.
Overspeed control is exerted in two main ways: aerodynamic stalling or
furling, and mechanical braking. Furling is the preferred method of slowing
wind turbines.
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Mechanical braking
A mechanical drum brake ordisk brake is used to hold the turbine at rest for
maintenance. Such brakes are usually applied only after blade furling and
electromagnetic braking have reduced the turbine speed, as the mechanical
brakes would wear quickly if used to stop the turbine from full speed. There
can also be a stick brake.
Turbine size
A person standing beside medium size modern turbine blades.
For a given survivable wind speed, the mass of a turbine is approximately
proportional to the cube of its blade-length. Wind power intercepted by the
turbine is proportional to the square of its blade-length. The maximum
blade-length of a turbine is limited by both the strength and stiffness of its
material.
Labor and maintenance costs increase only gradually with increasing turbine
size, so to minimize costs, wind farm turbines are basically limited by the
strength of materials, and siting requirements.
Typical modern wind turbines have diameters of 40 to 90 meters and are
rated between 500 kW and 2 megawatts. Currently (2005) the most powerful
turbine is rated at 6 MW.
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Generating electricity
For large, commercial size horizontal-axis wind turbines, the generatorismounted in a nacelle at the top of a tower, behind the hub of the turbine
rotor. A speed increasing gearbox may be inserted between the rotor hub and
the generator, so that the generator cost and weight can be reduced.
Commercial size generators have a rotor carrying a field winding so that a
rotating magnetic field is produced inside a set of windings called the stator.
While the rotating field winding consumes a fraction of a percent of the
generator output, adjustment of the field current allows good control over
the generator output voltage. Very small wind generators (a few watts to
perhaps a kilowatt in output) may usepermanent magnets but these are too
costly to use in large machines and do not allow convenient regulation of the
generator voltage.
Electrical generators inherently produce AC power. Older style wind
generators rotate at a constant speed, to matchpower line frequency, which
allowed the use of less costly induction generators. Newer wind turbines
often turn at whatever speed generates electricity most efficiently. The
variable frequency current is then converted to DC and then back to AC,
matching the line frequency and voltage. Although the two conversionsrequire costly equipment and cause power loss, the turbine can capture a
significantly larger fraction of the wind energy. In some cases, especially
when turbines are sited offshore, the DC energy will be transmitted from the
turbine to a central (onshore) inverterfor connection to the grid.
Materials
One of the strongest construction materials available (in 2006) is graphite-
fibre in epoxy, but it is very expensive and only used by some manufacturesfor special load-bearing parts of the rotor blades. Modern rotor blades (up to
126 m diameter) are made of lightweight pultruded glass-reinforced plastic
(GRP), smaller ones also from aluminium. GRP is the most common
material for modern wind turbines.
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Wood and canvas sails were originally used on early windmills.
Unfortunately they require much maintenance over their service life. Also,
they have a relatively high drag (low aerodynamic efficiency) for the force
they capture. For these reasons they were superseded with solid airfoils.
History
High-efficiency wind turbines (foreground) win out over traditional
windmills (background) in most new installations.
Wind machines were used for grinding grain in Persia as early as 200 B.C.
This type of machine was introduced into the Roman Empire by 250 A.D.
By the 14th century Dutch windmills were in use to drain areas of the Rhine
Riverdelta. In Denmarkby 1900 there were about 2500 windmills for
mechanical loads such as pumps and mills, producing an estimated
combined peak power of about 30 MW. The first windmill for electricity
production was built in Denmark in 1890, and in 1908 there were 72 wind-
driven electric generators from 5 kW to 25 kW. The largest machines were
on 24 m towers with four-bladed 23 m diameter rotors.
By the 1930s windmills were mainly used to generate electricity on farms,
mostly in the United States where distribution systems had not yet been
installed. In this period, high tensile steel was cheap, and windmills wereplaced atop prefabricated open steel lattice towers. A forerunner of modern
horizontal-axis wind generators was in service at Yalta, USSRin 1931. This
was a 100 kW generator on a 30 m tower, connected to the local 6.3 kV
distribution system. It was reported to have an annual load factorof 32 per
cent, not much different from current wind machines.
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In 1941 the world's first megawatt-size wind turbine was connected to the
local electrical distribution system on Grandpa's Knob in Castleton,
Vermont, USA. This 1.25 MW Smith-Putnam turbine operated for 1100
hours before a blade failed at a known weak point, which had not been
reinforced due to war-time material shortages. In the 1940s, the U.S. had a
rural electrification project that killed the natural market for wind-generated
power, since network power distribution provided a farm with more
dependable usable energy for a given amount of capital investment.
In the 1970s many people began to desire a self-sufficient life-style. Solar
cells were too expensive for small-scale electrical generation, so some
turned to windmills. At first they built ad-hoc designs using wood and
automobile parts. Most people discovered that a reliable wind generator is a
moderately complex engineering project, well beyond the ability of most
romantics. Some began to search for and rebuild farm wind-generators fromthe 1930s, of which Jacobs wind generators were especially sought after.
Later, in the 1980s, California provided tax rebates for ecologically harmless
power. These rebates funded the first major use of wind power for utility
electricity. These machines, gathered in large wind parks such as at
Altamont Pass would be considered small and un-economic by modern wind
power development standards.
In the 1990s, as aesthetics and durability became more important, turbines
were placed atop steel or reinforced concrete towers. Small generators areconnected to the tower on the ground, then the tower is raised into position.
Larger generators are hoisted into position atop the tower and there is a
ladder or staircase inside the tower to allow technicians to reach and
maintain the generator.
Originally wind generators were built right next to where their power was
needed. With the availability of long distance electric power transmission,
wind generators are now often on wind farms in windy locations and huge
ones are being built offshore, sometimes transmitting power back to land
using high voltagesubmarine cable. Since wind turbines are a renewable
means of generating electricity, they are being widely deployed, but their
cost is often subsidised by taxpayers, either directly or through renewable
energy credits. Much depends on the cost of alternative sources of
electricity. Wind generator cost per unit power has been decreasing by about
four percent per year.
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Companies in wind turbine industry
World market for wind energy plants in 2003
ABB Ltd. Wind turbine generators[3]
Airtricity only operates turbines AWS Truewind, LLC[4] - Wind Energy Consultants
Bergey Windpower[5] Det Norske Veritas - Certification of wind turbines and wind turbine projects
DeWind
Ecotcnia sccl - Spanish manufacturer
Eclectic Energy Ltd - UK manufacturer of small wind turbines, including the grid-linked turbine StealthGen
Eirbyte[7] Supplier of small turbines in Ireland
EMD A/S - WindPRO software package for project design and planning of turbines
Emergya Wind Technologies[8]
Enercon GmbH, Germany - wind turbines up to 6 MW
Gamesa Corporacion Tecnologica
Garrad Hassan and Partners Ltd.
General Electric, through its subsidiaryGE Energy
Hansen Transmissions Int. supplier of multi-MW wind turbine gear units[9]
O'Connor Hush Energy[10] - Australian supplier of small, quiet turbines
LM Glasfiber A/S - Rotor blades ranging from 13.4 to 61.5 m
Moventas Oy - Moventas provides leading mechanical power transmission
technology to the energy and process industries[11]
Natural Power- International wind energy consultancy services
NEG Micon - Merged with Vestas in 2004
Nordex
Pauwels Trafo Belgium/Ireland- Major Wind Turbine Generator TransformerManufacturers
PB Power- Global Engineering Company servicing Power industry
REpower, Germany - wind turbines up to 5 MW
Selsam Innovations / Superturbine Inc. , California multi-rotor wind turbines
http://www.selsam.com
Siemens Wind Power A/S (formerly Bonus Energy A/S)
http://en.wikipedia.org/wiki/ABB_Ltd.http://en.wikipedia.org/wiki/ABB_Ltd.http://www.abb.com/product/us/9AAC100348.aspx?country=EEhttp://www.abb.com/product/us/9AAC100348.aspx?country=EEhttp://en.wikipedia.org/wiki/Airtricityhttp://en.wikipedia.org/w/index.php?title=AWS_Truewind%2C_LLC&action=edithttp://www.awstruewind.com/http://www.awstruewind.com/http://en.wikipedia.org/w/index.php?title=Bergey_Windpower&action=edithttp://www.bergey.com/http://www.bergey.com/http://en.wikipedia.org/wiki/Det_Norske_Veritashttp://en.wikipedia.org/w/index.php?title=DeWind&action=edithttp://en.wikipedia.org/w/index.php?title=Ecot%C3%A8cnia_sccl&action=edithttp://en.wikipedia.org/w/index.php?title=Eclectic_Energy_Ltd&action=edithttp://en.wikipedia.org/w/index.php?title=Eirbyte&action=edithttp://www.eirbyte.com/http://www.eirbyte.com/http://en.wikipedia.org/w/index.php?title=EMD_A/S&action=edithttp://en.wikipedia.org/w/index.php?title=Emergya_Wind_Technologies&action=edithttp://www.directwind.nl/http://www.directwind.nl/http://en.wikipedia.org/wiki/Enercon_GmbHhttp://en.wikipedia.org/w/index.php?title=Gamesa_Corporacion_Tecnologica&action=edithttp://en.wikipedia.org/wiki/Garrad_Hassan_and_Partners_Ltd.http://en.wikipedia.org/wiki/Garrad_Hassan_and_Partners_Ltd.http://en.wikipedia.org/wiki/General_Electrichttp://en.wikipedia.org/wiki/GE_Energyhttp://en.wikipedia.org/wiki/GE_Energyhttp://en.wikipedia.org/w/index.php?title=Hansen_Transmissions_Int.&action=edithttp://en.wikipedia.org/w/index.php?title=Hansen_Transmissions_Int.&action=edithttp://www.hansentransmissions.com/http://www.hansentransmissions.com/http://www.hansentransmissions.com/http://en.wikipedia.org/w/index.php?title=O%27Connor_Hush_Energy&action=edithttp://www.hushenergy.com.au/http://www.hushenergy.com.au/http://en.wikipedia.org/w/index.php?title=LM_Glasfiber_A/S&action=edithttp://en.wikipedia.org/w/index.php?title=Moventas_Oy&action=edithttp://www.moventas.com/http://www.moventas.com/http://en.wikipedia.org/w/index.php?title=Natural_Power&action=edithttp://en.wikipedia.org/w/index.php?title=NEG_Micon&action=edithttp://en.wikipedia.org/w/index.php?title=Nordex&action=edithttp://en.wikipedia.org/w/index.php?title=Pauwels_Trafo_Belgium/Ireland&action=edithttp://en.wikipedia.org/w/index.php?title=PB_Power&action=edithttp://en.wikipedia.org/w/index.php?title=REpower&action=edithttp://en.wikipedia.org/w/index.php?title=Selsam_Innovations_/_Superturbine_Inc.&action=edithttp://en.wikipedia.org/w/index.php?title=Selsam_Innovations_/_Superturbine_Inc.&action=edithttp://www.selsam.com/http://en.wikipedia.org/w/index.php?title=Siemens_Wind_Power_A/S&action=edithttp://en.wikipedia.org/wiki/Image:Windenergy-marked.jpghttp://en.wikipedia.org/wiki/ABB_Ltd.http://www.abb.com/product/us/9AAC100348.aspx?country=EEhttp://en.wikipedia.org/wiki/Airtricityhttp://en.wikipedia.org/w/index.php?title=AWS_Truewind%2C_LLC&action=edithttp://www.awstruewind.com/http://en.wikipedia.org/w/index.php?title=Bergey_Windpower&action=edithttp://www.bergey.com/http://en.wikipedia.org/wiki/Det_Norske_Veritashttp://en.wikipedia.org/w/index.php?title=DeWind&action=edithttp://en.wikipedia.org/w/index.php?title=Ecot%C3%A8cnia_sccl&action=edithttp://en.wikipedia.org/w/index.php?title=Eclectic_Energy_Ltd&action=edithttp://en.wikipedia.org/w/index.php?title=Eirbyte&action=edithttp://www.eirbyte.com/http://en.wikipedia.org/w/index.php?title=EMD_A/S&action=edithttp://en.wikipedia.org/w/index.php?title=Emergya_Wind_Technologies&action=edithttp://www.directwind.nl/http://en.wikipedia.org/wiki/Enercon_GmbHhttp://en.wikipedia.org/w/index.php?title=Gamesa_Corporacion_Tecnologica&action=edithttp://en.wikipedia.org/wiki/Garrad_Hassan_and_Partners_Ltd.http://en.wikipedia.org/wiki/General_Electrichttp://en.wikipedia.org/wiki/GE_Energyhttp://en.wikipedia.org/w/index.php?title=Hansen_Transmissions_Int.&action=edithttp://www.hansentransmissions.com/http://en.wikipedia.org/w/index.php?title=O%27Connor_Hush_Energy&action=edithttp://www.hushenergy.com.au/http://en.wikipedia.org/w/index.php?title=LM_Glasfiber_A/S&action=edithttp://en.wikipedia.org/w/index.php?title=Moventas_Oy&action=edithttp://www.moventas.com/http://en.wikipedia.org/w/index.php?title=Natural_Power&action=edithttp://en.wikipedia.org/w/index.php?title=NEG_Micon&action=edithttp://en.wikipedia.org/w/index.php?title=Nordex&action=edithttp://en.wikipedia.org/w/index.php?title=Pauwels_Trafo_Belgium/Ireland&action=edithttp://en.wikipedia.org/w/index.php?title=PB_Power&action=edithttp://en.wikipedia.org/w/index.php?title=REpower&action=edithttp://en.wikipedia.org/w/index.php?title=Selsam_Innovations_/_Superturbine_Inc.&action=edithttp://www.selsam.com/http://en.wikipedia.org/w/index.php?title=Siemens_Wind_Power_A/S&action=edithttp://en.wikipedia.org/w/index.php?title=Southwest_Windpower&action=edit