Several participants in my design evaluation interviews indicated the interest in having audio as a medium to access the stream sensor data. As a result of this, I looked at options to use the ESP8266 chip in combination with a simple audio interface. I found some research on using the Wemos D1 for sound applications, a previously purchased microcontroller, the Adafruit Feather Huzzah can be expanded with the Music Maker FeatherWing, which adds an audio interface with a headphone jack output which could be used as a standalone version in the field.
Setting up the Adafruit Feather Huzzah
The Feather requires you to install a USB-driver (USB to UART Bridge VCP drivers) to work with your operating system properly. Note: For this install you need to restart your computer.
The Huzzah is part of the ESP8266 board manager, which needs to be added to the Arduino IDE under via Arduino…Preferences…Additional Board Manager URLs…
If step one and two have been successful, the Feather should be ready to be programmed with the Arduino IDE.
Arduino…Tools menu showing correct Board and Port to work with the Feather
Success. The Blink sketch is running smoothly on my Feather.
Feather Huzzah running the Blink script
I have ordered the Feather ordered at an earlier stage of the research project, but decided in the and not to chose it as the chosen as a central component of my project, mainly because of the price point (currently $33.00pp vs Wemos D1 $10.00pp on nicegear).
The Musicmaker shield adds another $36.00 to the sum.
For a complete audio player setup, an SD card (to store the mp3 files) and headphones are required. The MIDI setup does not require the SD card.
Adding the Audio Shield
Once the Musicmaker arrives I need to install some software as described in the guide by lady ada (2018):
Install the library for the Adafruit VS1053 Codec Breakout (lady ada, p.13).
Test the example code feather_player with two mp3 files on the SD card.
Solder the MIDI jumper on the bottom of the board together and test the MIDI example.
So far so good.
Now I need to connect the Feather to my MQTT network and have audio play triggered by a callback.
After some fiddling with the code, I manage to play the test Ocarina scale from the example code when the EC sensor and the water temperature sensor transmit data across the network.
The audio jar stands now among two visual outputs. While it offers a different mode of access to the stream data, it also breaks with the convention of having one-on-one relationships between input and output nodes.
I also need to consider if the jar casing is the best choice for this node, and how an audience would access the data in the field. The node could be a hidden audio jack that participants can plug their headphones into, or headphones can be provided. Alternatively, I could use a small speaker to play the sound output and make the experience accessible to multiple users at the same time.
The opportunities for this extra node need to be tested and evaluated in the field.
The design for the temperature visualisation is based on the concept of the previous paper circuit for the EC probe but uses coloured LEDs that indicate the water temperature in relation to stream health, as listed in the SHMAK manual by NIWA (2008). The idea for using cardboard and copper tape for these prototypes is inspired by the work by Jie Qi (2012) and the High-Low Tech Group at MIT Media Lab (2012).
Similar to the previous LED prototype I use a 12cm high sheet of white card paper as a base for my copper tape trails. During an evaluation discussion on the EC jar design, participant 18 suggested the use of coloured LEDs for future iterations. I am attempting to implement this suggestion in the design for the jar that visualises the data coming from the water temperature sensor (DS18B20).
During the ideation phase, I focused on a suitable way to connect coloured lights meaningfully to the water temperature readouts. Instead of opting for a traditional water temperature colour scale for blue (cold) and red (warm) I departed from the perspective of the stream, and what effect water temperature has on the more-than-human wellbeing of the stream.
Stream temperature is important because every species has a preferred temperature range. The range varies considerably from species to species. Sometimes, a temperature change is important, for example, as a trigger for egg hatching in some mayflies. Many organisms are unable to survive in temperatures above about 30 °C (except for some adapted to life in hot springs). At the other end of the scale, temperatures below freezing point constitute a very harsh environment because of the effects of ice.
A single temperature measurement is not particularly informative, but a series over time will provide a rough picture of the temperature regime in a stream. The longer the series and the closer together the measurements, the more informative the series will be.
Temperature depends largely on time of year and weather conditions. Stream type also plays a part. For example, lowland streams tend to experience quite stable temperatures (i.e., closely following average air temperatures). Shading along streams reduces the occurrence of extremely high water temperatures.
Water temperature fluctuates on a daily basis and for this reason it is suggested that measurements are always conducted at the same time of day.
Less than 5
Less than 5 oC
Values below 5 ºC are low and indicative of winter conditions in southern regions. Invertebrate and periphyton growth would be slow in such waters. Some species may be excluded.
5 to 9.9
5 to 9.9 oC
Values of 5 to 10°C are moderate to low and indicative of winter conditions. Most invertebrates and periphyton can survive well in these temperatures.
10 to 14.9
10 to 14.9 °C
Values of 10 to 15°C are very suitable for most invertebrates and periphyton.
15 to 19.9
15 to 19.9 oC
Temperatures of 15 to 20°C will start to be stressful for some invertebrates (e.g., stoneflies).
20 to 24.9
20 to 24.9 °C
Temperatures of 20 to 25°C are moderately high. Some invertebrates, such as some mayflies, stoneflies, and some fish, such as trout, are unlikely to survive such conditions for prolonged periods (e.g., several weeks).
25 to 29.9
25 to 29.9 °C
Temperatures between 25 and 30°C are likely to be stressful to fish, stoneflies, mayflies and some caddis flies. Such high temperatures may be a result of lack of shading and very sluggish flows.
30°C or more
30 °C or more
Temperatures over 30°C are likely to be very stressful to most stream life and result in their death. Again, such high temperatures may be a result of lack of shading and very sluggish flows. However, stream temperatures will rarely get to these levels.
Table 1: Habitat indicators of stream health. From NIWA (National Institute of Water and Atmospheric Research), 2008.
The table contains seven water temperature bands rated from poor to good. I opt to use one LED for each band, representing the ratings (poor, fair, good, excellent) with colour. I choose red, yellow and green LEDs to indicate the stream health rating:
To accelerate the development, I aim to build simple straight copper trails first as a proof of concept instead of spending time on developing a unique visual aesthetic for the circuit design without knowing whether the general concept works. I use the same circuit design as for the LED jar, but I need to recalculate the spacing for this version to fit eight rows of copper tape on the paper.
The Wemos D1 has seven digital outputs which makes it suitable for addressing seven LEDs individually. With the 8th digital output unused there is an opportunity for of adding a white LED on top later crossing all other outputs with sellotape, that could indicate the status of the network, similar to the EC jar.
The biggest challenge when making circuits with copper tape is the needs careful treatment and patience to make sure connections don’t break.
I use a craft knife to make precise cuts where the LEDs will be soldered in later.
I align the LEDs on the page so that the output can be seen best from one single perspective, that should later face towards an accessible area by the stream.
After all the LEDs are soldered into the circuit I test the quality of my solder points with a voltmeter.
Then I manually apply the forward voltage of each LED separately to test whether the connections work up until the edge of my circuit, where I will later add the connections to the microcontroller.
When working with SMD LEDs, I encountered some issues:
1: The LEDs are tiny and their polarity is barely visible from the top. Sometimes LEDs move during soldering or don’t connect properly. I need to make sure I don’t accidentally move or flip them when working on the circuit touching the circuit with my hands or the tip of my soldering iron.
2: The LEDs that I am using have a clear lens. I need to be careful to not mix up LEDs of different colours. The only way to know their colour is to power them on, which is tedious when dealing with the SMD form factor.
3: Components close to each other don’t work well with copper tape. There needs to be at least some centimetres of tape between two components.
In the sketch above you can see that my reference paper for the LEDs has moved in the process of adding LEDs which resulted in me picking the wrong LEDs for the first two rows. After removing the wrongly coloured LED I also realise that two green LEDs in series will not work for the “excellent” category as that would require a voltage of 2*2.2V which the microcontroller cannot supply. After making too many errors, I decide that I call it a day after testing that all the other LEDs work and will continue lab development after a healthy amount of sleep.
With this revised prototype I aimed to create a better, more stable design by inserting the LED and the photocell through holes into the hose while improving the sealing of electrical components from the beginning. I also wanted to use a cable with the actual length for use in the field and chose an approximately 2m long stranded core CAT-5 cable.
First I soldered the photocell to the green pair of cables and tested it with the code from yesterday.
I drilled 5mm hole into the hose to fit the LDR neatly.
The 3mm LED requires a 3mm hole respectively. I drilled the 3mm through the 5mm hole to make sure the holes are nicely aligned.
Reconnecting the wires with the breadboard from the previous prototype I ended up swapping the resistor to a 10k one which gave me more consistent readings when the LED was on half brightness.
For the sealing, I purchased the All Clear sealant that I have previously used for waterproofing my hydrophone. As opposed to hot glue, this material stays flexible when dried out and doesn’t run the risk of getting brittle.
Unfortunately one of the LED solder points was not well done, and I only discovered it after having added the sealant. With the cable disconnected, this prototype is unusable in the field, but the process of building it helped me understand possible avenues for improvement:
The design with the components stuck through tight-fitting holes is cleaner but needs to be revised with waterproofing in mind.
Solder points need to be stress tested and – if necessary re-done – before adding sealant.
Cables need to be fixed into place before adding sealant. Sealing might need to be re-done in the 3D workshop with proper ventilation and safety gear as this might require the use of turpentine.
Sealant might need to be changed as it might not be ideal in combination with cables/electronics.
For this research I want to explore what kind of DIY electronics can amplify the voice of the forgotten streams in Poneke/Wellington, New Zealand. As a first device I want to build a hydrophone that can be used during fieldwork to record underwater sounds.
Hydrophones used in scientific research, for acoustic monitoring, such as for tracking marine animals, are relatively expensive and even DIY solutions feature costly elements (see for example Dawson, 2012). In low-cost DIY solutions old audio components, such as headphones or radios are re-used (e.g. digifishmusic, 2008) and made waterproof with silicone or hot glue.
I decided to combine building a hydrophone based on two instructions. Both are based on using an electret microphone element as the primary component. In the instructions of Decker (2013) the element is enclosed in an empty film canister filled with mineral oil as a medium to optimize the hyrdophone. I chose this design for the first version following a suggestion on the Wellington Sonic Arts Facebook. The instructions by the University of Waikato (2011) feature a component list that is available in New Zealand.
Building the first version of the hydrophone took less than a day and involved researching the best possible option to be done within one day, sketching a schematic alongside a shopping list of necessary parts, planning the quickest route around town to buy all necessary parts and then 2 hours of soldering and assembling plus some extra time for testing and troubleshooting and documenting along the way.
I built the hydrophone as described in Decker (2013) but used a 3.5mm mono headphone jack at the end of the 3 meter long cable. I also soldered 3.5mm sockets to the pre-amp for in- and outputs to keep the device as modular as possible. For testing the hyrdrophone I used a pair of headphones, but I will be looking into options for adding a speaker. Currently, the pre-amp turns on and off by connecting and deconnecting the battery, which is cumbersome, so adding a switch would be a good improvement overall to be added to a (preferably waterproof) enclosure.
Dawson, S. (2012, January 20). Building the “CETOS” directional hydrophone. Retrieved from http://whaledolphintrust.org.nz/wp-content/uploads/Building-Directional-HPs.pdf
Decker, F. C. (2013, June). Underwater sound detection using sea perch through construction and operation of hydrophone. Retrieved from https://seaperch.byu.edu/wp-content/uploads/2013/06/Final.pdf
digifishmusic. (2008, January). How to make a Hydrophone (stereo!). freesound. Retrieved from http://www.freesound.org/forum/production-techniques-music-gear-tips-and-tricks/2631/?page=1#post13253
The University of Waikato, New Zealand. (2011, May 10). Make and Use a Hydrophone. Retrieved October 17, 2016, from http://sciencelearn.org.nz/content/download/20964/411858/version/7/file/Make+and+use+a+hydrophone.doc