Step 1: Parts Required
1. 5cm Dia. with 12cm long PVC Tubing
2. Propeller with mounting from GlobalWaters.com
3. Any Water TIght Compartment that is bigger than 6 x 15 x 5 cm
4. 12 oz. of Aquarium Type Sealant.
5. Zip Ties
6. A metal plating with a screw stud to mount the device onto the mussel bed.
1 x 0.01mF
1 x 1.0mF
1 x 10nF
2. Resistors :-
2 x 100ohm
2 x 10kohm
1 x 1kohm
3. 1 x EL-USB-3 Voltage Datalogger
4. 2 x 9V batteries
5. Multicolor roll of 14 Gauge Single Strip Wires( could use ribbon wires too)
6. 1 x 5x3 cm copper plated board.
7. 2 x Connector for 9V Batt
8. 1 x Melexis MLX90217 (Or any other Hall Effect sensor would work)
9. 1 x National Semiconductor LM2907
10. 1 x 7810 power regulator rated at 10V 1A max.
11. 1 x 2 pin switch (optional but recommended)
Step 2: The Board
( All positive lead should be connected to pin 3 of the 7810 power regulator and all ground to pin 2)
Step 3: Step 1 (continued)
The board on the left is the power regulator, the 7810, it is connected by two wires that runs to the main board, which is the middle board that contains the LM2907 and some resistors and capacitors that controls the maximum amount of revolutions that the circuit can take (which is around 830Hz) and also the ratio between the frequency to the corresponding voltage. The board on the right is the board that translate the mechanical movement of the fan into pulses that the LM2907 understand. It also contains a 10nF Capacitor and a 5.6kohm Resistor that reduces the noise in the circuit and also to protect the MLX90217 from any voltage spikes that might occurs when water do get into the circuit.
Step 4: The EL-USB-3
With a maximum of 32000 data points and a variable recording time, (from 1s to 24hrs), we either have a good idea of how speed changes in a small time frame or just take a sample at a long time interval that could keep the data logger running recording data for days. Furthermore, data downloading is easy with the USB connector, just pop it out of the box, download data, then pop it back into the box.
Future data logging would most likely be a wireless bluetooth type that would either be continuous live feed of data or keep the data in the device and then download data via bluetooth.
For the the current data logger, all data would then be downloaded into the computer and with the downloadable program that can be found on Lascar's website, data can be viewed in either raw data points or in graph form.
Step 5: Fan Enclosure
This method is a good way to ensure no mechanical failure could arise due to the fan spinning and also it reduces the amount of parasitic loss that could follow in a mechanical sensor, i.e a switch. As can be seen is the black box that stores all the electronics.
A hole is drilled through the box cover and the enclosure for the magnetic sensor to pass through and be able to detect the magnetic flux. Aquarium type sealant is used to seal the hole where the sensor passed through and around the base of the enclosure to the box to ensure proper sealing from seawater.
Step 6: Testing
The relationship between the revolutions and the velocity is found to be V = 0.0644 f - 0.0303 with a linear relationship with a +-1%. Which is good considering the data needed is only a rough data for a general idea of how flow speed affects the growth and production of mussel larvae.
For each device to be properly calibrated for more accurate measurements, a steady state flow test should be done for every one of the device. But it is not really require as the fan bought was made using a injected mold method that would ensure each fan would be the same.
Step 7: Testing 2
Here you can see the calibration of the frequency to the average flow velocity