Measuring Stream Velocity with Wireless Probes

The goal of the project is develop Bluetooth technology that can communicate wirelessly with 2 or more conductivity probes to measure small stream velocity. With the readout of the probes, probe settings, and software be accessible from a tablet or smart phone.

=Problem Definition=

Background


Measuring velocity in large stream channels have use a variety of successful means from current meter to acoustic devices. However these instruments do not work well in narrow, shallow, steep stream channels. For these shallow small streams various methods have been used. The simplest method uses a tennis ball or equivalent that is timed over a set distance. Small current meter are used but sometime are only partially submerged thus do not provide reliable measurements.

We currently use two conductivity probes connect with wires to microprocessor and a laptop computer. A salt solution is added to the water and salt solution pulse measured as it passes by the two probes which are separated by a set distance (2-4 meter). We use software to read and graphically-observe the microvolts readings of the conductivity probes which is related to the salt concentration. This technique has been success on small streams and even shallow rill flow on hillslopes.

Specifications

 * '''Stream Velocity
 * 2 L/min to approximately 4 cfs
 * '''Range of Communication
 * Approximately 6 stream widths between the probes
 * Bluetooth readings 100ft away from probes
 * '''Software
 * Peak to Peak calculations
 * Integration of curve with 5% error
 * Data exported to Excel for tablet access
 * Wireless data acquisition
 * 8 reading per second from each probe
 * At least 2 probes reading simultaneously
 * '''Additional Specifications
 * Lightweight
 * Long battery life
 * Weather proof housing
 * Withstand extreme temperatures

=Design Development= There are two main areas of design, the electrical engineering group, and the mechanical engineering group. The EE group works on the probe circuit and the app while the ME group works on the probe housing and waterproofing.

Initial Probe Design


In our initial design we used two Nanos, along with two HC-12 wireless serial communication modules, an HC-06 Bluetooth module, and two analog TDS probes. The probe on the secondary Nano would read the concentration of the solution in the water then send its data to the primary Nano through the HC-12 wireless communication. Then, the secondary probes data, along with the primary probes data would be sent to the smart device using the HC-06 Bluetooth Module. The smart device is also able to control the system through the Bluetooth communication.

After testing, this design quickly showed flaws that made it unusable. Each NANO has one serial communication port, and both the HC-06 and the HC-12 are trying to use the same serial communication at the same time on the primary NANO. We tried to get around this by using software serial, but this function is not able to switch between the two communications fast enough, and commands sent from the smart device would be missed. The HC-06 Bluetooth module also did not work with Iphones, this was a simple fix, we just upgraded to an HM-10 Bluetooth module.

So going into our first revision we had a decision to make. We could upgrade the boards to ones that would have multiple simultaneous serial communications, or we could figure out a way to use the Nanos. We eventually figured out that we could use three Nanos instead of two, and have data sent using I2C communication directly from one Nano to another.

Our initial app design was fairly basic. Consisting of a start, stop, and reset button, along with an input for the distance between the probes. This app would also give a graph of the concentration in the water in real time. It would then calculate the velocity when the data collection was stopped. The app would also show the voltages that each probe is reading in real time as well.

Our clients quickly gave us things to add to the app, including a save function, and a way to switch easily between distance measurements. We implemented these into the second design of the app.

Updated Probe Design
In our updated design we are using three Nanos instead of two to support the use of three separate serial communications simultaneously. In this design the data is taken from the secondary probe, and then sent to the sub-primary Nano from the secondary Nano through the HC-12 wireless serial communication. From there the data is sent to the primary Nano by direct I2C communication. From the primary Nano the data from both probes is sent to the smart device using the HM-10 Bluetooth module.

This design allows each Nano to only be using one serial communication, and does not increase the size of the circuitry by a large amount. The new HM-10 Bluetooth module also works flawlessly with all the devices that we tested with, and it also has a larger range than the HC-06.

The main concern with this design going forward is the power usage of having two Nanos instead of just one in the primary probe holder. We will do testing to see how long this can last on several different combinations of batteries, including a 9 volt battery, or 4 AA batteries.

The updated app design adds a save function. The user inputs the name of the file, and the app will save all the data into an excel sheet.

ME Design
=Final Design=

=Validation=

=Team Members=

=Additional Documentation=

Project Schedule

| Schedule

Meeting Minutes



Presentations

| Snapshot 1 | Design Review(Embedded video no longer works, see link below) | Snapshot 2 (Embedded video no longer works, see link below)

Videos

| Snapshot 2/Design Review Video

Other Documentation

| Budget | Design Validation