An anemometer is an instrument with metallic hemispheres revolving on a vertical rod used to measure speed of the wind. It is a meteorological device rarely used to determine the direction of the wind, developed by Italian architect, Leon Battista Alberti in 1450. Since then numerous versions of anemometer have been developed. Today a high quality anemometer is used to measure both wind pressure and velocity. Different versions of anemometer are widely used today.
The term “Anemo” is derived from the Greek word which means “wind”. Anemometers are of 2 types; One that measures the velocity of wind and the other the pressure of wind.
Wind velocity measurement is a major thing in many industries that deal in rotors of wind mill and its parts. Mostly they measure the wind velocity by using a wired anemometer.
In our project, we have used a buzzer that will be activated whenever the wind suddenly stops or the velocity of the wind is lowered. This will give an indication to the Wind Power Station that the wind is not present and the electricity cannot be generated. Thus the operator will come to know about the same.
Block Diagram:
Transmitter Unit:
Fig. 1: Block Diagram of Transmitter Unit of Scada based Wireless Anemometer
The block diagram shows the various parts that are included in the Transmitter Part. The transmitter is divided into 5 parts:
a) Anemometer.
b) Magnet and Reed Switch.
c) Transmitter circuitry (SC5262).
d) Battery.
e) Transmitting Antenna.
Receiver Unit:
Fig. 2: Block Diagram of Receiver Unit of Scada based Wireless Anemometer
The block diagram shows the various parts that are included in the Receiver Part. The Receiver is divided into 5 parts:
a) Receiving Antenna.
b) Power Supply of Receiver.
c) Receiver On/Off Switch and indicator
d) Receiver Circuitry (SC5272M4).
e) Pulse Indicator.
f) Activation Circuitry.
g) SCADA Software.
The mechanical part of the wireless anemometer consists of 3 parts; namely the rotating anemometer, the magnet attached to the shaft of the anemometer and the reed switch. Anemometer is the cup anemometer used having 3 arms. The magnet is attached to the shaft of the anemometer. The reed switch is placed near the magnet in such a way that the reed switch gets closed and open due to the Magnetic effect.
Anemometer:
Construction:
A simple type of anemometer, invented (1846) by Dr. John Thomas Romney Robinson, of Armagh Observatory. It consisted of four hemispherical cups each mounted on one end of four horizontal arms, which in turn were mounted at equal angles to each other on a vertical shaft.
Operation:
The air flow past the cups in any horizontal direction turned the cups in a manner that was proportional to the wind speed. Therefore, counting the turns of the cups over a set time period, produced the average wind speed for a wide range of speeds. On an anemometer with four cups it is easy to see that since the cups are arranged symmetrically on the end of the arms, the wind always has the hollow of one cup presented to it and is blowing on the back of the cup on the opposite end of the cross.
The other forms of mechanical velocity anemometer may be described as belonging to the windmill type or propeller anemometer. In the Robinson anemometer the axis of rotation is vertical, but with this subdivision the axis of rotation must be parallel to the direction of the wind and therefore horizontal. Furthermore, since the wind varies in direction and the axis has to follow its changes, a wind vane or some other contrivance to fulfil the same purpose must be employed. An aero vanecombines a propeller and a tail on the same axis to obtain accurate and precise wind speed and direction measurements from the same instrument. In cases where the direction of the air motion is always the same, as in the ventilating shafts of mines and buildings for instance, wind vanes, known as air meters are employed, and give most satisfactory results.
Reed Switch:
One important quality of the reed switch is its sensitivity, the amount of magnetic field necessary to actuate it. Sensitivity is measured in units of Ampere-turns, corresponding to the current in a coil multiplied by the number of turns. Typical pull-in sensitivities for commercial devices are in the 10 to 60 AT range. The lower the AT, the more sensitive the reed switches. Also, smaller reed switches, which have smaller parts, are more sensitive to magnetic fields, so the smaller the reed switch’s glass envelope is, the more sensitive it is.
i) Alarm.
j) Alarm Reset Circuitry.
SC5262 Remote Controller Encoder:
The SC5262 is a remote control encoder paired with SC5272 utilizing CMOS technology. It encodes data and address pins into a serial coded waveform suitable for RF or IR modulation. SC5262 has a maximum of 12-bits of tri-state address pins providing up to 531,441(or 312) address codes; thereby, drastically reducing and code collision and unauthorized code scanning possibilities.
Pin Diagram:
Fig. 2: Pin Diagram of SC5262 IC
Function Description
The SC5262 encodes the code address and data set at A0~ A5 and A6/D5 ~ A11/D0 into a special waveform and outputs it to the Dout when TE is pulled to “0” (Low state). This waveform is fed to either the RF modulator or the IR transmitter for transmission. The Transmitted radio frequency or infrared ray is received by the RF demodulator or IR receiver and reshaped to the special waveform. SC5272 is then used to decode the waveform and set the corresponding output pins. Thus completing a remote control encoding and decoding function.
Fig. 3: Table listing pin configuration of SC5262 IC
RF Operation:
Code Bits:
A code bit is the basic component of the encoded waveform, and can be classified as either an AD (Address/Data) Bit or a SYNC (Synchronous) Bit. An AD bit can be designated as bit “0”, “1” or “f” if it is in low, high or floating state respectively. One bit waveform consists of two pulse cycles. Each pulse cycle has 16 oscillating time periods. For further details, please refer to the diagram below: The Synchronous bit waveform is 4 bits long with 1/8 bit width pulse. Please refer to the diagram below.
Code Word:
A group of Code Bits is called a Code Word. A Code Word consists of 12 AD bits followed by one Sync Bit. The 12 AD bits are determined by the corresponding states of A0~A5 and A6/D5 ~ A11/D0 pins at the time of transmission. When Data Type of SC5262 is used, the address bits will decrease accordingly. For example, in the 3 Data Type where the address has 9 bits, the transmitting format is:
Table : Code Word
|
9 address bits
|
3 Data bits
|
Sync. Bit
|
SC5262/SC5272 has a maximum of 12 Address Bits including the 6 Address/Data bits. The following diagram shows the code bits with their corresponding pins.
The Code Bits A0~A5 and A6/D5 ~ A11/D0 are determined by the states of A0 ~ A5 and A6/D5 ~A11/D0 pins. For example, when the A0 (pin 1) is set to “1” (Vcc), the code bit A0 is synthesized as “1” bit. In the same manner, when it (A0 pin) is set to “0” (Vss) or left floating, the Code Bit A0 is synthesized as a “0” or “f” bit respectively.
Fig. 4: Table listing RF Data Bits and Synchronization
Code Frame:
A Code Frame consists of 4 continuous code Words. When SC5262 detects “0” on the (bar) TE, meaning the (bar) TE is active “low”), it outputs a Code frame at Dout. If (bar) TE is still active at the time the Code Frame transmission ends. SC5262 outputs another Code Frame. It should be noted that the Code Frame is synthesized at the time of transmission.
Fig. 5: Signal Diagram showing Code Frame
Single Resistor Oscillator:
The Building oscillator circuitry of SC5262 allows a precision oscillator to be constructed by connecting an external resistor between OSC1 and OSC2 pins. For SC5272 to decode correctly the received waveform, the oscillator frequency of SC5272 must be 2.5 ~8 times that of transmitting SC5262. The typical oscillator frequency with various resistor values for both SC5262 and SC5272 are shown below.
Features:
a. Low power consumption and very high noise immunity
b. Up to 12 tri-state code address pins or 6 data pins.
c. Wide operating voltage range (Vcc=3 V ~ 15 V)
d. Single resistor oscillator.
e. Latch or Momentary output type.
Block Diagram:
Fig. 6: Block Diagram of SC5262 IC
Circuit Diagram:
Fig. 7: Circuit Diagram of SC5262 IC based Transmitter Unit
Explanation:
The above figure shows the circuit diagram of the transmitter IC. The LC circuit forms the resonating circuit and the resonant frequency depends on the values of the Inductor and Capacitor selected. The value of the inductor is kept fixed and the value of capacitor is varied by using a simple variable capacitor.
The resonant frequency is given by the formula:
Where f= frequency,
L=inductor and
C=capacitance
The inductor at the leftmost part will act as a generator of electromagnetic waves. The inductor will release the energy stored in it in the form of EM waves and hence the transmitter will be able to transmit the pulses or signals.
The switch SW will be ON and OFF depending upon the reed switch operation. When the reed switch is ON, the switch SW will get closed and the pulse train will be transmitted and the equivalent signal will be converted into the EM waves.
Remote Control Decoder
Remote Control Decoder:
Description:
The SC5272 is a remote control decoder paired with SC5262 utilizing CMOS technology. It has a maximum of 12-bits of tri-state address pins providing up to 531,441(or 312) address codes; thereby, drastically reducing any code collision and unauthorized code scanning possibilities
Features:
a. Low power consumption and very high noise immunity.
b. Up to 12 tri-state code address pins or 6 data pins.
c. Wide operating voltage range (Vcc=3V ~ 15V).
d. Single resistor oscillator.
e. Latch or Momentary output type.
Application:
a. Home/automation security system.
b. Remote control toys or for industrial use.
c. Remote control fan.
d. Garage door controller.
Pin Configuration:
Fig. 8: Pin Diagram of SC5272 IC
Block Diagram:
Fig. 9: Block Diagram of SC5272 IC
Pin Description:
Fig. 10: Table listing pin configuration of SC5272 IC
Functional Description:
The SC5272 decodes the waveform received and fed into the Din pin. The waveform is decoded into code word that contains the address, data and Sync bits. The decoded address bits are compared with the address set at the address input pins. If both addresses match for 2 consecutive code words, SC5272 drives:
a). The data output pins whose corresponding data bits is then decoded to be a “1” bit
b). The VT output –to high voltage (high state).
RF Operation for SC5262
RF Operation:
Code Bits:
A code bit is the basic component of the encoded waveform, and can be classified as either an AD (Address/Data) Bit or a SYNC (Synchronous) Bit. An AD bit can be designated as bit “0”, “1” or “f” if it is in low, high or floating state respectively. One bit waveform consists of two pulse cycles. Each pulse cycle has 16 oscillating time periods. For further details, please refer to the diagram below:
Fig. 11: Signal Diagram showing Code Bits
a= oscillating period Bit “f” is only available for address bits
Fig. 12: Signal Diagram showing RF Data Bits
The Synchronous bit waveform is 4 bits long with 1/8 bit width pulse. Please refer to the diagram below:
Fig. 13: Signal Diagram showing Synchronous Bit Waveform
Code Word:
A group of Code Bits is called a Code Word. A Code Word consists of 12 AD bits followed by one Sync. bit. The 12 AD bits are interpreted as either address or data bits depending on the SC5272 version used. Please refer to the diagram below:
Fig. 14: Bit Values of a Code Word
IR Operation:
In the IR Type of operation, the functions are similar to the above descriptions except that the output waveform carried by SC5262-IR has a frequency of 38 kHz. Details are as follows:
Code Bits:
The Code Bits are further modulated with a 38kHz carrier frequency and can be”0”,”1” or “ f ” bit. Their waveform is shown below:
Fig. 15: Signal Diagram showing Code Bits
Code Word:
A Code Word is made up of code bits and the format is the same as that of the RF Code Word.
Code Frame:
Likewise, a Code Frame is made up of Code Words and the format is the same as that of RF type of operation.
Oscillator:
The SC5262-IR is specially designed for infrared remote control applications and its output waveform carries 38 kHz frequency. To get the 38 kHz carrier frequency at the data output, the oscillator frequency must be 76 kHz. A 440kW resistor connected between OSC1 and OSC2 pins of SC5262-IR is recommended. Moreover, for a matching decoder frequency, 1MW resistor connected between the OSC1 and OSC2 pins of SC5272 is also recommended.
Valid Transmission:
When the SC5272 receives a transmission code word, it initially checks whether this is a valid transmission. For a transmission to be valid, (1) it must be a complete code word, and (2) the address bits must match the address setting at the address pins. After two consecutive valid transmission, SC5272 (1) drives the data pins according to the data bits received, and (2) rise VT to high voltage(high state). The timings are shown in the following diagram.
Fig. 16: Signal Diagram for Valid Transmission of RF Data
Latch or Momentary Data Output Type:
The SC5272 uses either the latch or momentary data output type depending on the SC5272 version used. The latch type SC5272-LX activates the data out during transmission and this data is sustained in the memory until another data is inputted or entered. A momentary type (SC5272-MXon the other hand, activates the data out only during transmission. In the momentary type, the data does not remain in the memory after the transmission is completed. Please refer to the diagram below:
Fig. 17: Signal Diagram for Latch and Momentarily Data Output Type
Pulse Generation:
The anemometer rotates with respect to the wind velocity. If the wind velocity is very high, the anemometer will rotate very fast and if the wind velocity is very less, then the rotations will be less in a specific time interval. The magnet is attached to the shaft of the anemometer and a reed switch is placed near the anemometer shaft. Whenever the magnet placed on shaft comes near the reed switch, the switch gets closed and current flows in the circuit until the switch remains closed. As soon as the magnet goes away from the reed switch, the switch gets open and the circuit is broken and the current stops. So we get a pulse train with respect to the rotations of the shaft. A 9 volt battery is used to generate the current in the transmitter unit.
Pulse Transmission:
The pulse generated from the movement of the magnet and the reed switch is applied to the input of the transmitter unit. The IC used for this is IC SC5262. It is also called as the remote control encoder. The IC encodes the data and makes capable to be transmitted through an antenna. A battery is used to power up the transmitter unit. The IC has a unique data word and this data word should match exactly on the receiver side.
Pulse Reception:
The pulse transmitted through the transmitting antenna is received at the receiver through the receiver antenna. The received pulses are then sent to the IC SC5272M4. It is the Remote Control Decoder circuit. The data word on the receiver IC is exactly matched as that of the transmitter IC. So the data is decoded successfully and the pulse train is indicated on an LED. The LED glows ON and OFF according to the reception of pulses from the receiving antenna. When the On time period is going on, the Led will remain On and during the off time period, the Led will remain OFF.
The no. of pulses obtained during 1 exact rotation of the anemometer shaft can be adjusted by placing more no. of magnets around the anemometer shaft. If 2 magnets are placed opposite to each other on the anemometer shaft, then we get 2 pulses in 1 rotation of the shaft and hence the Led will glow twice in 1 whole rotation.
Pulse Time Distribution:
The pulse time period of the pulse train is divided into 2 parts; the ON time period and the OFF time period. During the ON time, the pulses are sent to the SCADA Communication System and during the OFF time, the alarm raising circuit gets connected through the Sugar Cube Relay.
SCADA Communication Working
SCADA Communication Working:
During the On time, the connection is made to the SCADA Communication System
As shown in below Fig. SCADA Communication system is a core component of a SCADA Monitoring System.
SCADA (Supervisory Control and Data Acquisition System) Communication can take place in a number of ways. The Process of Communication over a SCADA System involves several different SCADA System components like : sensors, control relays, Remote Terminal Units (RTUs) & finally SCADA Communication Networks.
Here is the basic key functions which is performed by SCADA system :
a. SCADA Data Acquisition: How the strategically placed sensors give the SCADA System visibility of critical operational process.
b. SCADA Data Communication: No SCADA communication system can function properly without a strong backbone. It involves the importance of reliable data network in a SCADA solution.
c. SCADA Data Presentation: If SCADA system can’t output accurate information then its is of no use to any human decusion makers. Data presentation is a critical part of SCADA.
d. SCADA Control: Some operations are much too massive or much too fast for humans to control directly. In this type of situation normal control system fails and here the actual power of SCADA system can be seen, because SCADA System conrols the system by using the data it collects to react automatically.
Fig. 18: Image showing principle of communication over SCADA
The SCADA will receive the pulses from the transmitter through the SC5272M4. Based on the no. of pulses received in 1 rotation, it will count them and display on the SCADA Screen. This will further calculate the wind velocity of the based on the no. of pulses going in the SCADA. The SCADA need a maximum of 5 volts to operate. So, during the ON time, the connection is made to SCADA and the amplitude of the pulses is kept well below the 5 volt range with help of appropriate resistance.
Hence, SCADA will give us the various parameters like wind velocity, pressure, temperature if appropriate sensors are used. In this case, we have used only the anemometer sensor.
Typical readings of the various parameters that are measured through SCADA are mentioned below:
Table : SCADA Parameters.
|
Sr.No.
|
Time
|
Wind Amp (amp)
|
Batt. Volt (volt)
|
H Press. (bar)
|
Temp (c)
|
Velocity
(Kmph)
|
|
|
1
|
00:16
|
0.06
|
23.23
|
1.31
|
28.4
|
21.6
|
|
|
2
|
00:32
|
0.06
|
23.19
|
1.34
|
28.16
|
19.2
|
|
|
3
|
00:49
|
0.06
|
23.2
|
1.37
|
27.92
|
32.8
|
|
|
4
|
01:05
|
0.06
|
23.18
|
1.34
|
27.67
|
20
|
|
|
5
|
01:21
|
0.06
|
23.14
|
1.37
|
27.55
|
18.4
|
|
|
6
|
01:38
|
0.06
|
23.16
|
1.31
|
27.31
|
31.6
|
|
|
7
|
01:54
|
0.06
|
23.16
|
1.31
|
27.19
|
40
|
|
|
8
|
02:10
|
0.06
|
23.14
|
1.37
|
27.07
|
12.8
|
|
|
9
|
02:28
|
0.06
|
23.2
|
1.34
|
26.83
|
16.4
|
|
|
10
|
02:44
|
0.06
|
23.34
|
1.4
|
26.59
|
25.2
|
|
|
11
|
03:01
|
0.06
|
23.44
|
1.34
|
26.35
|
22.8
|
|
|
12
|
03:17
|
0.06
|
23.24
|
1.34
|
26.22
|
20.4
|
|
|
13
|
03:34
|
1.35
|
23.55
|
1.37
|
26.1
|
30.8
|
|
|
14
|
03:50
|
0.06
|
23.23
|
1.28
|
25.86
|
24
|
|
|
15
|
04:06
|
0.06
|
23.14
|
1.34
|
25.74
|
10
|
|
|
16
|
04:23
|
0.06
|
23.16
|
1.37
|
25.5
|
16.4
|
|
|
17
|
04:39
|
0.06
|
23.12
|
1.37
|
25.26
|
21.6
|
|
|
18
|
04:56
|
0.06
|
23.21
|
1.34
|
25.14
|
25.6
|
|
|
19
|
05:12
|
0.06
|
23.16
|
1.4
|
24.9
|
28.4
|
|
|
20
|
05:34
|
0.06
|
23.12
|
1.31
|
24.65
|
14.4
|
|
|
21
|
05:51
|
0.06
|
23.11
|
1.34
|
24.53
|
12.8
|
|
|
22
|
06:07
|
0.06
|
23.09
|
1.31
|
24.29
|
9.2
|
|
Alarm raising Operation:
During the OFF time of the pulse, the switching is made and the alarm raising circuit gets connected. With the help of the potentiometer, the maximum limit of the OFF time is pre-decided and accordingly adjusted on the potentiometer.
A potentiometer is a variable resistor and the resistance can be changed according to the user’s wish. The user will pre-decide the maximum limit of the OFF time and if the time duration of the OFF time of the pulse gets exceeded than the preset limit, then the sugar cube relay will activate the alarm and the buzzer will start ringing.
Sugar Cube Relay:
This relay is known as the sugar cube relay because its shape is just like the cube of sugar. It is low cost relay for electric appliances.
It consumes relatively less power compared to other relays. It is compact in size and easily available for various current ratings.
It has 5 terminals, 2 for normally closed operations, 2 for normally open operations and 1 common terminal. This sugar cube relay which will act as a switch in the circuit either in normally closed mode or normally open mode. Common terminal will decide whether normally closed or normally open operation will be there.
Buzzer:
The Buzzer gets activated whenever the OFF time increases beyond the pre decided limit. The sugar cube relay will get activated and the buzzer will get connected to the main circuit. The Buzzer will ring until the RESET switch is pressed. As soon as the RESET switch is pressed, the Buzzer will get disconnected and the capacitor will be discharged.
Switching Between SCADA and Alarm Raising Circuit:
As shown in the below , the pulse train received at the LED is shown. It remains ON for a very short period and the OFF time is significantly higher than the ON time. During the ON time, the switching is done and the SCADA is connected to the circuit. The maximum amplitude of the pulse train is kept well below 5 V as SCADA cannot take input higher than 5 volts.
During the OFF time, the switching occurs and the alarm raising circuit is connected to the main circuit. Whenever the OFF time exceeds the pre decided limit, the alarm is raised and the buzzer starts ringing.
Fig. 19: Signal Diagram of Pulse Train at the Receiver
The alarm is switched off with the help of the RESET circuit and care has to be taken that the reset switch is pressed when the LED remains ON, or else the alarm will not get switched OFF.
In general, whenever the wind velocity will be lowered, the no. of pulses coming at the receiver will be less and the OFF time of the pulse train will increase. The alarm will get activated when this time exceed the pre decided value and the operator at the wind mill can come to know that the wind is not present and so the electricity would not get generated as the wind rotors will not rotate.
Fig. 20: Prototype of Wireless Anemometer
Fig. 21: Image of sensor circuitry used in Wireless Anemometer
Fig. 22: Image of transmitter circuitry of Wireless Anemometer
Circuit Diagrams
Filed Under: Electronic Projects
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