Build A SAS

This sub-surface automated dual water sampler (SAS) was designed, created, and tested by researchers at NOAA and the University of Miami to enable researchers to study water chemistry on shallow reef habitats to further our understanding of conditions in coral reef ecosystems. The SAS was also designed to minimize some of the financial hurdles present in marine research by acting as a low-cost open-source alternative to other existing automated water samplers. To do this we used free design software, 3D printed unique components, and built the "brain" of the sampler from a Teensy microcontroller. The Teensy is compatible with the Arduino IDE and it's simplified version of C++, making futher development and changes to the code easier for people not well-versed in computer coding. The open-source design will continue to be developed and improved on by NOAA and University of Miami researchers, and any updates will be made available on this website. This site is meant to serve as an exhaustive resource for any group to build, program, deploy, and troubleshoot their own water samplers. The build and operation manuals can be downloaded here, along with the sampler code, 3D printing design files, laser cutting files, and circuit board design files.

Below you will find 5 sections that provide detailed information on how to build a sub-surface automated dual water sampler. The sections are:

Important downloads

● (3) Endcap

● (2) Motor Mount

● (2) Motor Mount Adaptor

● (1) Internal Frame

● (2) 4mm pump head roller carriage

● (1) Acrylic Face Plate (Testing the sampler housing for leaks will require 3 face plates)

Base Material: FR-4 TG130

No. of Layers: 2 layers

PCB Dimensions: 61.85 mm x 43.65 mm

No. of Different Designs: 1

PCB Thickness: 1.6 mm

PCB Color: Black

Surface Finish: HASL

Minimum Solder Mask Dam: 0.4 mm↑

Copper Weight: 1 oz.

Minimum Drill Hole Size: 0.3 mm

Trace Width / Spacing: 6/6 mil

Blind or Buried Vias: No

Plated Half-holes / Castellated Holes: No

Impedance Control: No

Print and cut all parts listed in the 3D Printed Components and Laser Cut Components lists in the Resources and materials section above.

Take the three end caps and use sand paper to sand away any tabs and roughen the surface on the inner walls of the cap (See Image 1). All of the surfaces to be attached with epoxy or other adhesives will be sanded first to improve adhesion.

Cut the 2” PVC Schedule 40 piping into one 6.75” long section and two 2.25” long sections. Sand the first inch or two of the outer edge of each piece of PVC as well as the lip of the piping to help the adhesives bind (See Image 2). Also sand the inner edges of the PVC Tee fitting. Use a cloth or paper towel moistened with isopropanol to clean off all sanded areas on the PVC and 3D printed components and allow to dry (water can be used instead of isopropanol but more care will be needed to ensure the sanded areas are clean). Check the depth of the PVC piping on the PVC fitting and the 3D printed caps (it should be about 1.4” on the PVC Tee and 0.6” on the cap) and put a strip of tape on the sections of PVC to keep the edges of the glued and epoxied areas clean.

Apply PVC primer to the insides of the two opposite PVC Tee fitting holes and to one side of each of the two inch long PVC sections. Apply PVC cement to the newly primed areas on the PVC Tee fitting and the two inch PVC sections and push the PVC parts into the fitting until fully inserted giving a quarter twist. Stand up the newly cemented PVC fitting and weight the top section to add pressure to the parts, clean up any excess PVC cement and remove tape, and then leave to cure for at least 15 minutes. Next add PVC primer to the inside surface of the middle PVC Tee fitting and one side of the longer PVC section (See Image 3). Add PVC cement to the same surfaces and then push the PVC section into the fitting until fully inserted giving a quarter twist. Stand up the PVC Tee and weight the top section to add pressure to the parts, clean up any excess PVC cement and remove tape, and then leave to cure for at least 2 hours for a full cure.

The 3D endcaps will be epoxied onto the free ends of the PVC sections using a two-part epoxy. Be cautious to not get epoxy on the O-ring face of the endcap as that could create problems making the housing watertight later on. Ensure proper mixture of the two-part epoxy (See Image 4) and then add epoxy to the corner of the entire wall of the inside of one of the endcaps and along the lip and upper edge of one of the short PVC pieces (See Image 5). Smooth out the epoxy to ensure consistent coverage across the inner walls of the endcap and the outside end of the PVC pipe. Push the two pieces together until the PVC is fully inserted giving a quarter twist to remove any gaps in the coverage of the epoxy. Make sure the tabs of the endcap are oriented at 45 degree angle from the long PVC section so that the body of the housing doesn’t get in the way of accessing the tabs (See Image 6). Be careful not to let the endcap shift in position or slide off the PVC section. Clean off any excess epoxy from both the outside and the inside edges of the endcap and then flip the housing over. Use the same method to epoxy an endcap to the opposite free PVC section. With both endcaps on, stand the PVC frame up with one endcap on a flat surface and the other pointing up. Again, clean off any excess epoxy. Place a weight on the raised endcap to apply pressure to the PVC/endcap joins (See Image 7), remove the tape, and leave for 18-24 hours for a full cure.

After the epoxy on the first two endcaps has cured use the same method described above to epoxy the third endcap onto the free end of the long PVC section. Clean off any excess epoxy and then stand the PVC frame on the new endcap, weight the top to apply pressure, then remove the tape. Leave for 18-24 hours for a full cure.

Testing the housing for leaks

Once the adhesives are all fully cured the housing can be checked for leaks using three of the acrylic faceplates. Install four #6-32 x 1 inch long stainless steel screws into each of the endcaps in the threaded tabs. Lightly lubricate the three -227 O-rings with a silicone lubricant and install one into each of the three endcap O-ring grooves. Remove the plastic layer from the side of the laser cut acrylic face without the scored circle in the center. Place an acrylic face plate onto the mounting screws on each endcap, plastic layer facing out, and secure using four #6-32 lock nuts.

Please note, to create a watertight seal the nuts only need to be hand-tight and the O-ring will visibly deform and seal against the acrylic. Overtightening the nuts can break the 3D printed endcap, or the acrylic face plate, or both.

Place the now sealed housing into a bucket of water and hold beneath the surface or weight it down. Look for any streams of bubbles escaping the housing as an indicator that water is getting in and the housing is leaking. When you remove the housing look for any signs of water intrusion inside the housing. If there is a leak, determine where it is located. Leaks on the epoxy may be repairable by adding a line of epoxy to the edge of the endcap/PVC connection. Leaks at the O-ring/acrylic seal may be evidence of a damaged O-ring or dust, hair, or another particle on the O-ring or in the O-ring groove preventing a proper seal.

Attaching the adaptor

Wiring the Motors

Mounting the Motor

Building the internal armature

Remove 1/8 inch of the insulated sleeve on a four inch length of red 26 AWG wire. Solder the end of the wire onto the free positive terminal on the 9 volt dual strap (See Image 15) and add ½ inch of heat shrink tubing onto the solder to strengthen the connection. Route the new red wire through the upper left hand hole and push the dual strap into position in the battery compartment of the frame (See Image 16).

The original black and red wire should be led through their respective channels in the frame to the outside of the battery compartment. The dual strap should be secured using two #2-56 x ½ inch long screws and two #2-56 nuts. Strip the last 1/8 inch of the insulated sleeve of each of the 3 wires and attach a KK crimp terminal to the end. Install the wire terminals into a 3-hole female KK connector with the new red wire (6 volts) on the outside edge, the original red wire (12 volts) in the center, and the original black wire (negative) on the inside (See Image 16). A piece of heat shrink, a ziptie, or a piece of tape can be wrapped around the set of wires to keep them together.

To make connections for the OLED and the IR Sensor take the seven different colored 26 AWG wires and strip 1/8 inch off each end of the wires. On one end of each wire attach a DuPont female crimp pin, on the other end of each wire install a KK crimp terminal. Plug four of the wired KK crimp terminals into a 4-hole female KK connector and plug the other ends (with the DuPont pins), in the same order, to a 4-hole DuPont connector housing (See Image 17). Plug the KK crimp terminals of the other three wires into a 3-hole female KK connector and the three DuPont pins in the same order to a 3-hole DuPont connector housing.

Image 18

To better understand the design and function of the SAS circuit board prior to construction, the schematic and diagram in Image 19 can be examined to trace the track of the circuit between components and compare it with the board's layout. Understanding the circuit isn't crucial to construction of the SAS but it is helpful to perform advanced troubleshooting or alter the open-source design for other purposes.

With a home milled circuit board vias must be installed and soldered into the board. If the circuit board is purchased online the vias are likely already installed. To install the vias, take 1 inch long sections of wire filament and place through each of the 1/64 inch via holes and bend in half to keep in place (See Image 20). Any wire filament from discarded wire, like the excess from the reed switch can be used for this task. Once all via wires are in place, solder them to the board being careful to heat both the wire and the copper of the circuit board to prevent cold solders that might break up conductivity. It’s easiest to solder all the via wires on one side of the board before flipping it over to solder the others. Using flush cutters remove any excess wire and solder from the vias.

Install the header pins for the Teensy 3.5 and flip the board over and solder the header pins to the board, being careful to keep the headers straight up and down so that the board fits (See Image 21). To double-check, flip the board back over and place the Teensy on the pins to see if any are out of alignment. Remove Teensy for now, it will be the last piece to be soldered to the circuit board.

Use a flat edge to bend the pins of the resistors and diodes at right angles. Install the resistors to the board and solder the top of each of the resistor pins. While direction of the resistors is unimportant, placement is, so be sure to double-check the location of each resistor before installing (See Image 22). Keep the resistors as low to the board as possible to save space. Install the diodes with the cathode (gray stripe) facing the outer edge of the board (toward the motor connection) and solder the pins onto the board. Direction with diodes is very important so be sure to double-check that they are installed in the correct orientation (See Image 23). Flip the board over and solder the other side of the resistor and diode terminals and then use flush cutters to remove excess pins and solder.

Install the male KK connectors onto the top of the circuit board (See Image 24) and flip the board over. Be sure KK connectors are installed straight up and down and then solder the pins to the board.

Prepare the microSD card

The Teensy 3.5 microcontroller can log data on a microSD card inserted in the Teensy’s microSD slot. This is where the general settings for the sampler will be stored and where all the data will be recorded, including temperature, time and date of pump alarms firing, and codes for sampler troubleshooting. For the microSD card to communicate with the Teensy properly, two blank text files need to be uploaded to the card prior to using it. The two text files should be titled “dataLog.TXT” and “sampleParam.TXT”. On the sampleParam.TXT file type the following three lines of code to input initial settings for your water sampler:

1,10,10,100,1 1,0,1,1,18 1,15,1,1,18

Once the text files have been added to the microSD card it can be inserted into the slot on the Teensy.

Follow the instructions on the Teensy website to setup both the Arduino and Teensy software on your computer. Be sure to download a version of the Arduino software that is compatible with the Teensy software (e.g. Arduino 1.8.8).

Once both the Arduino and Teensy software are installed, download the code for the SAS and place it into a new folder within the Arduino libraries folder, found in the Arduino folder in the Documents folder. The folder the code is placed in needs to match the name of the code for it to work with the Arduino software. For example, if the code file is named "brainV2B.ino", name the folder "brainV2B".

Next, the necessary Arduino libraries need to be added to allow the SAS code to function properly. Run the Arduino software and select the Sketch menu. Select "Include Library" and then "Manage Libraries" and the Library manager window will pop up. Search for "Adafruit_MCP9808 library" in the search bar and install the most recent version of the library. The installation process will place the library in the same Documents folder as the SAS code. Next search for the library called "SdFat" and install the most recent version. The last library required for the SAS code should already be installed. Open up the "hardware" folder inside the Arduino folder and then go into the "teensy" folder, open up the "avr" folder, and then the "libraries" folder. Look for the "Adafruit_SSD1306" folder. On a Mac the Arduino icon can be selected with a right-click to bring up the drop menu, then select "how Package Contents", the "Contents" folder, "Java" folder, "hardware" folder, from which point the process is the same as described above.

Once the Adafruit_SSD1306 folder is found, or placed into the libraries folder, open the Adafruit_SSD1306.h file with a text editor (e.g. Notepad or TextEdit) and scroll down to the following line:

--------------------------*/ // #define SSD1306_128_64 #define SSD1306_128_32 // #define SSD1306_96_16 /*========================*/

The default setup will be the 128 x 32 bit screen resolution. The SAS resolution needs to be 128 x 64 bit. To fix this, uncomment the 128 x 64 bit screen resolution by deleting the two forward slashes in front of SSD1306_128_64 and add two forward slashes in front of SSD1306_128_32 so it looks like this:

--------------------------*/ #define SSD1306_128_64 // #define SSD1306_128_32 // #define SSD1306_96_16 /*========================*/

Once finished, save and close the text file. The last step in preparing the code for use is to edit the code for the SAS's sleep mode. This code minimizes the amount of current draw while sleeping so the SAS can be deployed for long periods of time. The following edits allows sampling alarms to be set in advance for a larger range of time (years rather than weeks). In the same Libraries folder as Adafruit_SSD1306, open the folder labeled Snooze and then the folder labeled Utility. Use a text editor to edit and save these two files: SnoozeAlarm.h and SnoozeAlarm.cpp. In SnoozeAlarm.h find the line near the bottom of the document that looks like:

void setRtcTimer( uint8_t hours, uint8_t minutes, uint8_t seconds );

Change that line to:

void setRtcTimer( uint32_t hours, uint32_t minutes, uint32_t seconds );

In SnoozeAlarm.cpp find the line near the top of the document that looks like:

void SnoozeAlarm::setRtcTimer( uint8_t hours, uint8_t minutes, uint8_t seconds ) {

Change that line to:

void SnoozeAlarm::setRtcTimer( uint32_t hours, uint32_t minutes, uint32_t seconds ) {

The SAS code is now ready to be uploaded onto the Teensy microcontroller. Open the Arduino software, also called the Arduino Integrated Development Environment (IDE), and select the Tools menu. Select "Board:" and choose Teensy 3.5; this step is necessary the first time you open Arduino so the program knows which type of microcontroller is being programmed. From the File menu select "Open…" and navigate to the Arduino library folder, where the SAS code was saved, and open the code file. When the code has opened on the Arduino IDE click the verify button to compile the code for uploading to the Teensy. Once the code is compiled the Teensy program (Teensyduino) will automatically open. Connect the Teensy to the computer using the micro USB port. Under the Arduino Tools menu go to "Port" and choose the serial port that the Teensy is plugged into. Press the tan reboot button next to the microSD card slot on the Teensy (See Image 19) and then click on the upload button on the Teensy program to upload the SAS code to the Teensy. Once the upload is complete the circuit board is now ready and can be connected to the sensors and the screen to verify its function.

Typically when the Teensy is plugged into the computer for the first time it does not appear as a serial port option until after a file has been uploaded. If no serial port is available, complete all of the other steps above and, once the SAS code is uploaded, a serial port should then be available on the Arduino program. To ensure the code was loaded properly, push the reboot button on the Teensy again and re-upload the SAS code. This should only be necessary the first time a Teensy microcontroller is connected to a computer.

Place the circuit board into the armature with the battery and temperature breakout board down. The coin cell holder and the temperature breakout board will stick out of the frame slightly through their customized openings. Put on the circuit board cover and secure in place with the #2-56 x 3/4 screw. The screw head will be flush with the lid and the tip of the screw will just start to exit the back of the armature. Attach the KK connectors to the board for the Reed switch, IR sensor, and OLED (See Image 28). Reverse the wire order for the OLED by twisting the wires and then plug the 4-hole DuPont connector onto the OLED pins. Plug the 3-hole DuPont connector onto the IR sensor pins in the same order as it's KK connector. Insert the microSD card. Finally, attach the KK connector for the battery connection.

Note that attaching the power before the OLED, IR sensor, and Reed switch might interfer with the function of those components, so always attach the power last.

Fill two of the 4AA battery packs with fully charged batteries and insert battery packs into the sampler to snap into the 9-volt dual battery strap. The battery pack below the power connection to the circuit board should always be plugged in first (see Image 29) followed by the second battery pack. The sampler will turn on automatically, ready for programming using the IR remote. Looping a rubber band under the battery packs and hooking it on the power connection hardware will help ensure the batteries don't disconnect from the 9-volt connector if the internal armature gets jolted. Attach the two motor KK connectors to the circuit board. The connection for Pump A is on the left and Pump B on the right. Slide the complete armature into the housing (See Image 30) and secure with four #6-32 lock nuts.

Making the Neoprene Sample Bags

Cut the neoprene according to the dimensions in Image 31 (the dimensions are shown in mm). Then fold the neoprene along the depicted dotted lines. Next fold the neoprene in half and install grommets in the two top corners of the bag (See Image 32). Each sampler requires two of the neoprene protective bags. A Tedlar sample bag should be placed in the folded contours of the protective bags with as few creases as possible. The valve of the Tedlar bag comes out of both holes in the neoprene to secure the neoprene flap. Attach a six inch length of Tygon tubing from the outflow of the pump to the stem of the Tedlar bag valve using the neoprene slits to secure the tubing and minimize valve movement during deployment (See Image 33).

For instructions on programming and deploying the sampler please refer to the SAS Operation Manual or visit the USE A SAS page.