Overview
The Windmeter is an anemometer designed to measure and record wind speed distribution from 0 to 17+ meters per second. It was designed for high reliability, ease of construction, and for a wide environmental range. Data is logged over a period of 30.46 days (1/12 of a year), and then saved for 11 months. The data can be retrieved with a laptop computer any time within the 12 months of logging. The Windmeter is self-powered by a solar pannel and battery. Calibration of the Windmeter can be done against a car's speedometer or better yet a GPS receiver. The Windmeter should cost you under $300 Can. to make.Skills Required:
- General Electronic Knowledge
- SMD Soldering
- PCB Prototyping (Single layer)
- General Mechanical Knowledge
- Wood working / power tool / hand tool usage
Mechanics of the Windmeter / Anemometer
Description
The Windmeter / Anemometer is constructed from common parts and supplies. The design is simple and easy to build. The internal frame is made of wood and the external moving parts are plastic and metal. All electronics are housed inside the Windmeter and thus protected from weather. The only difficult part to get is the MAXI Kinder surprises. They are available at Christmas and Easter or all year from a specialty store listed in the parts list. The rotating assembly rides on two standard shielded NOT sealed roller blade bearings. Shielded bearings have less friction than sealed. Replacement roller blade bearings are available at most sports stores.Assembly
Read the entire document before beginning construction. Complete the circuit board first before the making and assembling the mechanical parts of the Windmeter. If serious problems arise during construction, re-read the entire document again. If this fails to solve your problem you can email me at "drwho at infidigm dot net". I may not respond to all questions. Step 1 Begin by cutting the following pieces out of the ply-wood as shown.
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 Step 2 Screw the pieces together with 8-1.25" screws. | ||
 Step 3 Drill 4 holes in the wooden assembly, 2 in each side, 3/4" from the edge and 1.75" from the corner with a 5/16" drill bit. | ||
 Step 4a Cut another piece of wood 8" x 15". | ||
 Step 4b Mount the piece of wood as shown with the same 8-1.25" screws. | ||
 Step 4c Slide the wooden assembly down the pipe so that the top of the pipe is 13.25" from the top of the wooden assembly. Be sure that the pipe is square to the wooden assembly and that the 45 deg side touches the pipe. Re-drill the holes in the wooden assembly to go through into the pipe. Mount the wooden assembly to the pipe by inserting the 5" x 1/4" bolts though the holes and tighten the nuts. | ||
 Step 5a Mount the Solar panel as shown with the same 8-1.25" screws. Be sure that the Solar panel top surface is even or slightly above the top of the 8"x15" wood piece. | ||
 Step 5b Silicon around the Solar pannel and mounting screws to make it water proof. | ||
| Step 6 Drill a 1/4" hole in the side of the pipe, just below the wooden assembly for the wires for the solar panel. (See Step 4 picture.) | ||
 Step 7 Using a compass, draw two 3" circles on the ply-wood. Cutout the circular shapes with a jig-saw and then sand them so they will fit in the 3" pipe. | ||
 Step 8 Draw a line along the diameter of one of the cutouts. Mark for drill holes at the center and at a 1/4" from both sides along the diameter. | ||
 Step 9 Clamp the two cutout pieces together so the edges are flush. Place the marked one on top. Drill 3 1/4" pilot holes through both pieces. | ||
  Step 10 Drill the center hole with a 7/8" wood bit. Do not go all the way through. Drill just deep enough so that half of the 608 bearing sits inside the wood as shown. | ||
 Step 11 Now drill out the three holes with a 1/2" drill bit. Their should be no wood left between the outside holes and the outside of the 3" cutout. | ||
 Step 12 Drill another 1/2" hole 90 degs to the others to allow the wires to pass through the cutouts. | ||
 Step 13 Cut 2 pieces of 1/2" wooden dowel to 6" long. Mark measurements on the dowels as shown. | ||
  Step 14 It is necessary to glue the assembly together inside the pipe so that it will easily slide in and out. Insert one of the circular cutouts with the bearing notch facing out. This cutout will now be called the bottom cutout. Slide it three inches into the pipe. Place the two 1/2" wooden dowels down though the bottom cutout. Now pass the top remaining cutout through the dowels to just above the 7/16" markings. You should have something that looks like the left picture. Apply epoxy to the both dowels at the top 7/16" markings. Slide the top cutout overtop of the 7/16" markings. Slide the whole assembly into the end of the pipe as shown in the right picture. Be sure that the upper cutout is square to the pipe and that the dowels are still in the right place. Wait 15 minutes for the epoxy to harden. | ||
  Step 15 Remove the assembly and re-insert the opposite way with the top in first. Put the bottom cutout part way into the pipe as shown in the left picture. Apply epoxy to both dowels at the bottom 7/16" markings. Slide them down until they are flush with bottom cutout as shown in the right picture. Be sure that the cutout is square to the pipe. Wait 15 minutes for the epoxy to harden. | ||
 Step 16 Mount the electronic circuit board to the assembly as shown with the hall effect sensor facing the 5/16" shaft. Try to keep the hall effect sensor centered around the 5/16" shaft. Space the board 3/16" away from the 1/2" dowels. Be careful that the board will clear the pipe when the assembly is inserted into the pipe. | ||
 Step 17 Cut a piece of 3/16" x 1" wood to 3.5" in length. Epoxy the piece flush to the top of the 1/2" dowels, opposite the circuit board. Wait 15 minutes for the epoxy to harden. Insert the assembly into the pipe until the 3/16" x 1" wood piece catches the top of the pipe. Mark the pipe where the piece touches. Cut one notch on each side of the pipe, 1" deep. The assembly should now slide flush into the pipe as shown. | ||
 Step 18 Cut the 5/16" steel rod to 7" in length. Put a M8-1.25mm thread on one end of the 5/16" rod. Make the threads about 1" in length. | ||
 Step 19 Destroy the third 608 bearing by crushing it in a vise. Only the inner race is needed for the next step. Epoxy the inner race to the 5/16" shaft 2.5" down from the threaded end. Epoxy the magnet in place with the NORTH pole facing out. Be sure that the magnet is directly in front of the hall effect sensor with the shaft in place. | ||
 Step 20 Epoxy the two 608 bearings in place in the wood. Slide the 5/16" shaft in place to align the bearings. Try to keep the bearings as centered as possible in the 7/8" cutout. Be sure that no epoxy runs down into the inner race or it will destroy the bearings. | ||
 Step 21 Take the 4" PVC pipe cap and mark the exact center. Drill a 5/16" or 11/32" hole in the center. (What ever size will fit the 5/16" shaft the best.) | ||
 Step 22 Draw three lines on the top of the 4" cap that originate from the center. Draw the lines 120 degs apart and continue the line 1/2" down the side of the cap as shown. Mark 3 lines (one on each 120 deg line) 1/4" down from the top of the pipe cap, perpendicular to the 120 deg lines as shown. | ||
 Step 23 Drill three 1/4" holes parallel to the top of the pipe cap at each of the markings as shown. | ||
 Step 24 Take the three smaller halves of the plastic kinder surprise shells. Mark on each of them their diameter (center/middle line) 1/2" up each side. Then mark a line 3/16" up from the edge on each side perpendicular to the diameter markings. Drill a 1/4" hole in each side of each shell at the markings. | ||
 Step 25 Cut 3 pieces of the 1/4" steel rod to 9" in length. Slide a kinder surprise shell over each of the 9" 1/4" steel rods as shown. Leave 1/16" sticking out past the end. | ||
 Step 26 Insert the other ends of the 1/4" rods into the 4" PVC pipe cap as shown. The rods should extend 1/4" past the inside wall of the pipe cap. Make the cups (ks shells) face all the same way for clockwise rotation. Be sure that the cups are straight up and down. Epoxy the 1/4" rods to the pipe cap both inside and out. Epoxy the rods to the cups on both sides, inside and out. | ||
 Step 27 Using a knife or sandpaper, make the surface around the 11/32" hole in the center of the pipe cap flat for the washers to sit on. Attach the pipe cap to the 5/16" shaft with a M8 nut and washer on both sides of the cap. Tighten the nuts together. Silicone the top nut to seal the hole in the cap. | ||
  Step 28 Find out the length of the tower the windmeter will be mounted on. Cut a length of catagory-5 cable (network cable) that is slightly longer than the tower (max 200 feet = 61 meters). Take two of the four pars of wire and strip the four wires. Twist the two white (return) wires from both of the pars together and solder them to pin 5 on the serial connector. Connect one of the remaining wires to pin 2 and the other remaining wire to pin 3 on the serial connector. Slide the other end of the cat-5 cable up through the pipe (on the windmeter) from the bottom to the top. Take the same two pars on this end and strip the four wires. Look at the parts placement diagram and connect the white wires to the connector on the circuit board marked Pin 5. (Two places - use both) Connect the remaining wire that is soldered to pin 2 on the serial connector to the connector on the circuit board marked Pin 2. Due the same for the remaining Pin 3 wire.Note: It is necessary to use cat-5 cable opposed to regular telephone cable due to EMI. It was noticed that when regular telephone cable was used, the windmeter would reset during lightning storms. Using cat-5 in this manner solved the problem. | ||
   Step 29 Pull the excess wire from the solar panel out of the pipe. Cut a 4" and a 12" length of wire from the excess. Put female tabs one end of the 4" piece to connect to the battery. Strip the other end. Strip one end of the 12" piece. Solder one of the 4" wires to one of the 12" wires and to one of the solar panel wires. Solder the other 4" wire to the other 12" wire and to the other solar panel wire. Wrap the connections in black tape. Strip 1/8" of the other end of the 12" piece. Measure the voltage on the two wires to determine which is positive and negative. Look at the parts placement diagram to see where to connect the wires on the connector on the circuit board. Connect the (+) tab to the (+) on the battery and then the negative tab.If these wiring instructions are confusing, hopefully this diagram clears things up.  |
Parts List
| Quantity | Description | Supplier | Part No. |
| 1 | 5 min Epoxy | Home Depot | B 110-607 |
| 1 | 3" ABS Pipe - 6' length | Home Depot | A 120-784 |
| 1 | 4" PVC Pipe Cap | Home Depot | 650-580 |
| 1 | 2'x2' - 1/2" plywood | Home Depot | C 434-561 |
| 1 | 1/2" wood dowel - 2' length | Home Depot | A 115-256 |
| 1 | 5/16" Steel Shaft - 36" length | Home Depot | 142-006 |
| 1 | 1/4" Steel Shaft - 36" length | Home Depot | 142-004 |
| 1 | 8-1.25" wood screws (10) | Home Depot | 846-052 |
| 2 | M8 1.25mm Nuts | Home Depot | (BIN# 128522) 670-008 |
| 2 | M8 Washers | Home Depot | (BIN# 128558) 730-008 |
| 2 | 5" 1/4"-20 bolts | Home Depot | (BIN# 124228) 275-326 |
| 2 | 1/4"-20 nuts | Home Depot | (BIN# 131585) 083-114 |
| 3 | Maxi Kinder Surprise Shells | Mike's General Store - Winnipeg | 2002 CHRISTMAS KINDER MAXI EGG |
| 1 | 3/16"x1" balsa wood - 6" length | Hobby store | |
| 1 | 608 bearings (Roller blade) - shielded | Sports Center |
Tools Needed
Here is a list of the major tools that were used to make the mechanical parts of the Windmeter.- Small Drill Press or Drill
- 1/2" Drill bit
- 1/4" Drill bit
- 5/16" Drill bit
- 11/32" Drill bit
- 1/4" Drill Bit
- 7/8" Wood Drill Bit
- Hack-saw
- Jigsaw
- M8-1.25mm die
Electronics for the Windmeter / Anemometer
Circuit Description
SchematicThe circuit for the Windmeter is self powered. A 12v solar cell array provides power to the circuit and charges the battery during the day. At night the 12v battery is used to power the circuit. Operation for many days without sunlight is required, so the circuit operates at 3.3v and uses a high efficiency switching power supply. The circuit draws 1.35 mA at 12v. The circuit should operate for over 50 days without sunlight from a fully charged battery. The solar cell will take 3 days to fully charge a dead battery. The circuit should never loose power.
Power enters the circuit through L7 and D1 to prevent reverse battery connection. C10 is used as a input filtering capacitor while C11 is used as a input de-coupling capacitor. U3, L1, D2, and C12 form the switching power supply. R3, R6 and R7 form the low battery power down.
A magnet and Hall effect sensor are used to measure RPM of the rotating cups. One pulse per revolution is produced. The sensor is on the back of the PCB and the magnet is attached to the rotating shaft. Microcontroller U2 is used to calculate wind speed from the pulses produced by the Hall sensor. The micro also records the varying speeds and provides a interface to a Laptop / computer. U1, a low power RS232 1 channel driver, is used to join the PC serial port and the micro's UART. C2 - C5 are used by the RS232 Driver IC to form charge pumps. C1, C6, C7, C13 are used as bypass / de-coupling capacitors throughout the circuit. C8, C9 are used to help start oscillation. The crystal of 4.096 Mhz was selected for easy and accurate time measurement. R1, R2 are used to form a voltage divider which feeds ADC channel 0 to measure Supply voltage. Q1 and Q2 control the power applied to R1 and R2 to improve power consumption.
Assembly
The PCB Gerber files are provided. Use Bare Bones PCB to manufacture the circuit board for you. It cost less than $100. Here are instructions for using Bare Bones PCB service
Once you have received the PCB, population is next. Please review the Top Parts Placement diagram and the Bottom Parts Placement diagrambefore beginning and throughout assembly. Begin by soldering U1 and U2. U2 is a 0.031" pitch and U1 is a 0.0255 pitch. Please see Infidigm's soldering guide for instructions on soldering small pitches. Next solder U3 which is a SO8 package. Continue by soldering L1, D2 and D1. Solder all resistors, capacitors and ferrite chips being mindful of Polarized Caps C10 (Bar = Neg-) and C12(Bar = Pos+) polarity. Solder the crystal, connector and the programming connector on the top side of the board. Place hall effect sensor, C8 and C9 on the back side of the board and solder in place. Fold the hall effect sensor so that it is flat against the circuit board as shown.Programming
Programming the microcontroller is the next step. The micro is a AVR ATmega88 made by ATMEL. An AVR ISP (Incircuit Serial Programmer) compatible programmer is required. Here is a list of programmers.- STK500 Development board (Search for STK500) .
- AVRISP In system programmer (Search for ATAVRISP2) .
For STK-500 and ATAVRISP2
- Brown-out detection level at VCC = 2.7V;
- Ext. Crystal Osc.; Frequency 3.0-8.0Mhz; Start-up time: 16K CK/ 14 CK + 65ms;
The Program
Only read this section if you wish to modify the program!The program is written in C. It consists of one C file and was written to be complied under the free AVR-GCC C compiler (WinAVR 3.4.6 April 21, 2006). Read the beginners guide to learn how to install GCC. Once you have GCC working, download the Project Files for Programmers NotePad. and unzip them to a directory of your choosing. Run Programmers NotePad ( /WinAVR/pn/pn.exe). In PN go "File-->Open Project(s)" and select "windmeter.pnproj" in the directory where you unzipped "windmtr.zip". Open "windmtr.c by double clicking on it. Click "Tools-->Make All" to test the Compiler. The program is well documented and self explanatory.
Parts List
The list includes all parts for the Windmeter electronics. All part numbers are for Digikey unless their is a link to another supplier.| Quantity | Value | Description | Digikey Part No. | Component |
| 1 | ATmega8 | Microprocessor | ATMEGA88-20AU-ND | U2 |
| 1 | Max3221 | 1-CH RS-232 | 296-9595-1-ND | U1 |
| 1 | MA785 | Schottky | MA2Z78500LCT-ND | D1 |
| 1 | DN6852 | Hall Effect Sensor | DN6852A-ND (testing 620-1043-ND) | U4 |
| 1 | LTC1474IS8-3.3 | Voltage Regulator | LTC1474IS8-3.3#PBF-ND | U3 |
| 1 | MBR0520L | Schottky 20v, 0.4A | MBR0520LCT-ND | D2 |
| 1 | UNR2111 | PNP 100mA preset gain | UNR211100LCT-ND | Q1 |
| 1 | UNR2211 | NPN 100mA preset gain | UNR221100LCT-ND | Q2 |
| 1 | 220uF | Electrolytic Cap | EEU-FC1H221 | C10 |
| 7 | 0.1uF | SMD Cap | PCC1828CT-ND | C1-5,C7,C13 |
| 1 | 330uF | Niobium Oxide Cap | 478-1830-1-ND | C12 |
| 1 | 1UF | Ceramic Cap | 490-1800-1-ND | C6 |
| 1 | 4.7UF | Ceramic Cap | 478-1570-1-ND | C11 |
| 2 | 22pF | SMD Cap | PCC220CNCT-ND | C8,C9 |
| 2 | 1nF | SMD Cap | 445-1337-1-ND | C14,C15 |
| 1 | 22K | SMD Res | RHM22.0KCCT-ND | R1 |
| 1 | 3.3K | SMD Res | RHM3.30KCCT-ND | R2 |
| 1 | 100K | SMD Res | RHM100KCCT-ND | R3 |
| 1 | 220K | SMD Res | RHM220KCCT-ND | R6 |
| 1 | 33K | SMD Res | RHM33.0KCCT-ND | R7 |
| 2 | 1K | SMD Res | RHM1.00KCCT-ND | R4,R5 |
| 1 | 100uH | SMD Inductor | 308-1503-1-ND | L1 |
| 1 | 6 pin | 0.1" Terminal Block | 277-1277-ND | Connector |
| 6 | 2.7K@100Mhz | Ferrite Chip | 490-1051-1-ND | L2-7 |
| 1 | 4.096 Mhz | Crystal | 300-8471-ND | Y1 |
| 1 | 6 pin | 0.1" header 2x3 | WM6636-ND | Prog Port |
| 1 | 9 pin | DB-9 Connector | A23108-ND | |
| 1 | 12v, 2.2Ahr | Sealed Lead Battery | P171-ND | |
| 1 | Manufactured Circuit board | Advanced Circuits | Bare Bones PCB | |
| 1 | 2.2 Watt, 12v | Solar 12v panel | 11-1883-6 | Canadian Tire |
| 1 | ~ 8mm dia | N - S Magnet |
Tools and Supplies for circuit assembly
- Soldering Iron (35 watt) with fine tip.
- Solder Sucker
- Solder (Better quality than Radio Shack)
- AVR ISP Programmer
Files
Windmeter SchematicPCB Gerbers
Top Parts Placement diagram
Bottom Parts Placement diagram
All Program Project Files.
C Source Code
Hex file for ATmega88
ATmega88 Data Sheet (Microprocessor)
MAX3221 Data Sheet (RS232 Line driver)
Switching Regulator Data Sheet
Calibration and Usage
Usage
Once the Windmeter is fully assembled, connect it to a laptop or computer via the 9-pin serial port. Open the program Hyper Terminal. Set up a Direct connection for the COMM port that the Windmeter is connected to for 9600-8-N. Go File-->Properties-->Settings Tab-->ASCII Setup Button, and under ASCII receiving click 'Append line feeds to incoming line ends'. 'OK' back to the main screen. Pressing any key will cause the menu to appear. The menu has 7 options. Each option is selected by pressing the corresponding key. Be sure that Caps Lock is turned off.- [g]et data Pressing 'g' will prompt for which month to get the data for. Use the arrow keys to select the appropriate month and then press Enter. The recorded speed distribution for the corresponding month is displayed as well as with the maximum speed for that month.
- [c]lear data Pressing 'c' will prompt to confirm deleting all recorded data over the past 12 months.
- [s]et month Pressing 's' will prompt for which month to begin logging at. Use the arrow keys to select the appropriate month and then press Enter. What ever data is in the month that is selected is cleared to zero. This function is used to sync the Windmeter with the calendar.
- [i]nfo Pressing 'i' will display a list of items.
- Firmware version
- "Logging Month" is the month that the windmeter is currently logging to.
- "Days logged" is the aproximate day of the month
- "# of resets" is the number of times the micro has reset since the month was set (pressing 's') Reset notification is necessary because thier is some data lost if a reset has occurred. Resets are caused by power loss or by a very close lightning strike.
- Current wind speed
- Shows the supply voltage from the battery and solar cell. A fully charged battery should measure around 12.85v (in the dark). A very low charge is 11.50 or less. In the sunlight, the supply voltage can measure between 12.5 - 17 volts.
- Current programmed Offset (b)
- Current programmed slope (m)
- [m]slope Pressing 'm' allows programming of the slope variable. It is used by the Windmeter to calculate speed. This allows calibration. The value of m can be determined in the Calibration section. m is written to EEPROM so it's value is preserved during power loss.
- [b]offset Pressing 'b' allows programming of the offset variable. It is used by the Windmeter to calculate speed. This allows calibration. The value of b can be determined in the Calibration section. b is written to EEPROM so it's value is preserved during power loss.
- [t]toggle calibration mode Pressing 't' will toggle calibration mode ON and OFF. When in calibration mode a 5 digit number is displayed once per revolution of the Windmeter. This number represents the time it takes for one revolution. The data is used in the Calibration section for determining variables m and b.
- [r]eset Pressing 'r' resets the device thus restarting the program.
Calibration
Calibration of the Windmeter requires two people and a few steps. It can be done with a car or truck on a day with no wind. If possible check the speedometer of your vehicle with a GPS receiver. Begin by mounting the Windmeter 1 meter/yard above the top of the vehicle. This will avoid effects from the vehicles aerodynamics. Connect the Windmeter to a laptop and put it into calibration mode. Get one person to drive and the other to record data (A good safety consideration). Bring the vehicle to 10 km/hr and wait for the Windmeter readings to stabilize. Record three samples in the provided Excel Spreadsheet. Bring the vehicle to 15 km/hr and repeat until the spreadsheet is filled.Once the spreadsheets is filled out, 'm' and 'b' can be determined. The entered data should have formed something close to a straight line. Start by adjusting 'm' on the spreadsheet so that the slope of the ideal line and the measured line are the same. Next adjust 'b' so that the measured line moves overtop of (eclipses) the ideal line. The goal of this process is to align the measured line with the ideal line as close as possible. Repeatedly adjust 'm' and 'b' until you are satisfied. Program 'm' and 'b' into the Windmeter and turn Calibration mode off. The Windmeter is now ready for installation.
Once the Windmeter is installed, (1) clear all the data, and (2) set the appropriate month. If possible set the month at the very beginning of the calendar month. This will aligned the windmeter to the calendar day of the month.
Lightning Protection
Lightning protection is mandatory because the serial cable runs from the top of the tower to the bottom. This is a very attractive path for lightning. Protection is accomplished by placing a large metal object (long rod, sheet metal, car springs) half a meter/yard in the ground beside the tower. It is recommended that salt be sprinkled around the metal to help conduction into the ground. Attach a steel rod (2 - 5 cm in dia, > 30 cm in length) to the back of the ply-wood box on the Windmeter. Connect the rod and the metal object in the ground with at least 1/4" aircraft cable. This method will provide a better, more attractive path in the event of a lightning strike.
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