Build a SlopeShift wind logger

1. Tools and parts

Tools

• Soldering iron, solder, and a damp sponge or brass wool
• Safety glasses for everyone soldering or cutting
• Wire strippers, side cutters, small pliers
• Multimeter (resistance and continuity)
• Hot glue gun, craft knife or scissors, a drill for the PVC caps
• A computer with the Arduino IDE, and a 3.3 V USB-serial adapter
• A phone compass

Parts

Safety

• Hot iron: put it back in its stand every time. Hold parts with pliers, not fingers.
• Solder in a ventilated room. Wash your hands after handling solder.
• Glass reed switches crack easily. Bend their leads with pliers, a few millimetres from the glass, never at the glass.
• Count the magnets in and out at every session. Store them on a steel plate or in a closed box.

2. The vane ring

Eight reed switches sit in a ring under the vane shaft. A magnet on an arm turns with the shaft and closes the switch it sits over. Halfway between two switches it closes both, which is how eight switches give sixteen directions.

1. Cut a disc of stiff plastic or thin plywood for the ring base. Mark its centre and draw eight lines 45° apart. Label them, going clockwise seen from above: N, NE, E, SE, S, SW, W, NW.
2. Glue a reed switch along each line, the same distance from the centre. The magnet must pass close over each one. Ring diameter and gap: check. Start with the switches about 2–3 cm from the centre and the magnet a few millimetres above the glass.
3. Fit the 608 bearing at the centre so the shaft turns freely.
4. Glue one magnet to a short arm on the shaft. Point the magnet arm the same way as the vane's pointer. Then when the pointer faces north, the magnet sits over the N switch.
5. Make the vane: a light fin cut from a jug at the back, a pointer at the front. Balance it on the shaft so it doesn't lean. A balanced, light vane turns in the 1–3 mph winds that slope thermals bring.

Test before wiring. Put the multimeter on continuity across one switch and move a magnet over it. It should beep. Move the magnet away. It should stop. Test all eight.

3. Solder the resistor ladder

Each switch connects pin A0 to ground through its own resistor. A 10k pull-up, powered from pin D4 only while reading, completes the divider.

1. Measure every resistor before you solder it. Mixing up two values gives wrong directions that are hard to find later. Use 1% resistors: E and ENE are only 9 ADC counts apart.
2. Join one lead of all eight switches into a common ground wire.
3. Solder each switch's other lead to its resistor. Join the far ends of all eight resistors into a common A0 wire.
4. Insulate each joint with heat-shrink or tape.
5. Check the ladder. Measure between the A0 wire and the ground wire. With no magnet it should read open (no value). Hold the magnet over N: about 33 kΩ. Between N and NE: about 6.6 kΩ (the two in parallel). Go around the ring.
6. Solder the 10k pull-up from D4 to A0 on the Pro Mini.

4. Cups and magnet

1. Cut three ping-pong balls in half. You need three halves.
2. Fix three equal arms to a hub, 120° apart. Glue a cup to the end of each arm, all open sides facing the same way around the circle.
3. Put the hub on its shaft through the second 608 bearing. It should spin for a few seconds after a flick.
4. Glue the second magnet to the hub, off-centre, so it passes the cups reed switch once per turn.
5. Glue the cups reed switch to the post where the magnet passes over it. Gap: check. Spin it slowly by hand with the multimeter on continuity: one beep per turn.
6. Solder the reed between D2 and GND. Solder the 100 nF capacitor across the reed. It stops one closure counting as several.
7. Mount vane and cups at opposite ends of a crossbar, at least 30 cm apart, so neither disturbs the other.

5. The housing

Wire the clock and memory to the Pro Mini:

1. Two fixes on the ZS-042 clock module. Remove its power LED. Remove its charging resistor (or use a rechargeable LIR2032), because it tries to charge the coin cell and a normal CR2032 must not be charged. Your teacher can show you which parts on your module; boards vary, so check against a photo of yours.
2. Remove the Pro Mini's power LED to save battery.
3. Put the boards and battery holder in the 1½" PVC tube. Leave the Pro Mini's six-pin programming header where you can reach it by taking off the top cap.
4. Drill a small drain hole in the bottom cap so condensation can escape.
5. Run the vane and cups wires along the crossbar and down the mast into the tube. Seal where wires enter with hot glue.

6. Flash the firmware

1. Install the Arduino IDE. No extra libraries are needed.
2. Open slopeshift.ino (in the firmware/slopeshift folder of the kit files).
3. Choose Board: Arduino Pro or Pro Mini, Processor: ATmega328P (3.3V, 8 MHz).
4. Switch the AA holder off. Connect the 3.3 V USB-serial adapter to the six-pin header (GND to GND, matching the pin labels). Use 3.3 V only; a 5 V adapter can damage the clock and memory.
5. Click Upload.

7. Set the clock: time

1. Open the Serial Monitor at 9600 baud, line ending Newline.
2. Press Enter to wake it. It prints slopeshift ready and a list of commands. It goes back to sleep after 30 seconds with no typing.
3. Type the local time, 24-hour, at the moment you press Enter: time 2026-10-21 14:05. It answers ok, logging from the next minute.
4. Type status and check the time is right.

The clock has no daylight saving. Set it to the time you'll use when reading the data. The tools fix the time zone later.

8. Calibrate speed: k

Speed = cup turns per second (Hz) × k. The default is 1.492 mph per Hz, which fits SparkFun's cups, not homemade ones. To find yours:

1. On a calm day, a teacher or another adult drives at a steady 10 mph on a quiet, safe road. A student in the passenger seat holds the cups out of the window, well clear of the car, and runs live.
2. Write down the Hz readings. Repeat at 20 mph.
3. k = mph ÷ Hz at each speed. Average them.
4. Save it: k 1.85 (use your number). It's stored in memory and kept when the battery is out. Values from 0.1 to 20 are accepted.

No car? Compare against a handheld anemometer in front of a fan, at two or three distances. Or leave the default: switch times come from direction, so they don't need an exact speed.

9. The live check

Type live. Every 2 seconds for 30 seconds it prints the direction, the raw reading (adc), the cup rate in Hz and the speed:

Turn the vane slowly through all 16 directions and compare with this table. Within a few counts is fine.

Then spin the cups by hand: Hz should rise and fall with speed.

Classroom demo: fast. Point a fan or hairdryer at the vane. Type fast: it prints s,dir,deg,mph every 2 seconds. After 10 seconds it knows the "before" wind. Move the fan to the other side and hold it there. About 8 seconds later it prints a line like # switch at 34 s: NW -> SE and blinks three times. That's the same rule the tools use on a real day, sped up. Press any key to stop. Logging carries on underneath. You can paste the lines into a spreadsheet and chart them.

10. Deploy it

1. Put the logger up a week or more before you need the data. A memory chip holds about 20 days.
2. Mount it on a stake or tripod at the height you care about, clear of trunks, walls and branches. They bend the wind.
3. With the phone compass, turn the whole crossbar so that when the pointer faces north, the magnet sits over the N switch.
4. Switch the AA holder on. Watch the LED:
   • 2 slow blinks: logging. Good.
   • 5 fast blinks: the clock isn't set. Run time.
   • 8 fast blinks: memory full. Read the log, then clear yes.
5. Note the place, latitude and longitude, the slope angle and the direction it faces. The Analyzer needs these.
6. Leave it. To collect, type dump in the Serial Monitor and save the text as a .csv file, or use the kit's Python tool: slopeshift.py read --port /dev/ttyUSB0 -o wind.csv. Then load the file into the Analyzer.

11. Troubleshooting

Still stuck? Write down what status and live print and ask your teacher.