Resources and materials needed
● (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
● (12) #6-32 x 1" Faceplate screws
● (2) #2-56 x 1/8 OLED screws
● (2) #2-56 9V snap nuts
● (1) Two-Part Marine Epoxy
● (1) Acrylic solvent cement
● (1) Silicone lubricant
● (3) 11” long cable tie
● (1) RTC Coin Battery Holder
● (3) 1N4001 Diode (2)
● (2) 1K 1% resistors
● (1) 3.3K 5% resistors
● (1) 390K 1% resistors
● (1) 100K 1% resistors
● (16) KK Crimp Terminal
● (7) Dupont female crimp pins
● (1) Spool Solder (Lead-free)
Building the waterproof housing
Prepare the parts
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.
Setting up the motors and motor mounts
Attaching the adaptor
To mount the 12V 170RPM Econ Metal Gearmotor in the sampler it needs to be attached to the 3D printed motor mount adaptor. Use sandpaper to roughen the top of the body of the motor (See Image 8A) and the inside surface of the adaptor. Use a cloth or paper towel dipped in isopropanol to clean off the sanded surfaces of the motor and the adaptor and let dry. Put a bead of two-part epoxy around the top of the body of the motor and around the inside of the adaptor. Push the motor into the adaptor giving a full turn and stop so that the flat end of the adaptor is flush with the motor face (See Image 8B). Clean off any epoxy that has made it onto the face of the motor, keep the motor and adaptor face flush, and let the epoxy cure for 18-24 hours before using the motor.
Wiring the Motors
Remove the last 1/2 inch of the insulated sleeve from one end of a 15” length of each red and black 22 AWG wire and twist onto the positive (red) and negative (black) terminal on the back of the motor. Solder the wires onto the terminals and cover with a 1/2 inch of heat shrink tubing for added stability. On the opposite end of each 15” wire remove the last 1/8 inch of the insulated sleeve and connect a KK crimp terminal. Install the crimped wire into a 2-hole female KK connector with the red wire on the left side (See Image 9). Repeat for the second motor.
Mounting the Motor
The motor mount needs to be sanded smooth before being used. Starting on the outside face of the motor mount (the side without the X-ring groove), use a rough sandpaper to sand the surface until it appears uniform and smooth. Using a high grit (e.g. 600 grit) wet/dry sandpaper, wet sand the inside edge of the motor mount (See Image 10A). Once the surface seems uniform and smooth, clean and dry the motor mount. Lightly lubricate the -007 X-ring and install into the X-ring groove on the inside of the motor mount. A pen cap, screw head or any other small object without sharp edges can be used to push the X-ring into place and ensure it sits flat in the groove. Once the X-ring is installed push the shaft of the motor into the X-ring so that the motor and adaptor are flush to the inside wall of the motor mount. Holding the motor flush to the motor mount, use four #4-40 x 1/2" screws to secure the motor (See Image 10B). Again, only tighten screws hand-tight. Overtightening screws may strip the holes or break the 3D printed motor mount.
Check for water tight seal again
To ensure the seal on the housing is water tight with the addition of the motor mounts, install the motors into the two short sections of the PVC housing (See Image 11A). The motor wires will need to be led through the housing to open end of the long PVC section. A simple way to do this is to tape a light weight to the end of the wires so gravity will pull the wires through to where they will later connect to the main circuit board and power source. The O-rings on the endcaps should all be lightly lubricated and the motor mount should only be tightened to hand-tight to create a water-tight seal and prevent breakage. If the acrylic face plate was removed from the endcap on the long section of the housing it should be replaced and secured again as described in the previous water test. Using freshwater, hold the housing underwater and look for any streams of bubbles. If any water enters the housing examine all O-rings and X-rings for dirtiness or signs of damage. If water does enter the housing and the motors become wet, remove from the housing and allow to dry thoroughly before using to prevent damage to the motors.
To install the 3D printed roller carriage for the pump heads, open the two unsealed pump head and remove the existing carriage wheel. Carefully pull apart the carriage wheel, remove the rollers and place on the 3D printed roller mount, and clip the shaft and rollers back into the original top piece of the carriage wheel. Using a synthetic lubricant, heavily lube the back of the carriage wheel and the rollers (See Image 11B) and then reinstall into the pump head. To mount the pump head onto the motor line up the flat edges of the motor shaft and the pump head shaft housing and then install the shaft into the pump head. Make sure that the pump head lines up with its outline on the motor face mount and then secure in place with two #6-32 x 1 1/8" screws (See Image 11C).
A step that will be useful when using the sampler later on is to label the housing next to the pumps “A” and “B” using a permanent marker or a waterproof label. This will help ensure that the pump is connected to the correct terminal and that the calibration settings for each pump are accurate. Similarly, labeling the KK connectors on the motor wires will also makes it easier to connect the pumps properly when that time comes.
Building the internal armature
Use a rough sandpaper to sand all surface of the 3D printed internal frame to smooth out surfaces and remove any resin tabs. Make sure that the face of the frame, where the OLED, IR sensor, and reed switch are mounted, is sanded until smooth and uniform, then use a high grit wet/dry sandpaper to wet sand the face of the frame further. Clean and dry the frame.
Remove only the center circle from the plastic layer on the laser cut acrylic face plate (See Image 12). Coat the face of the frame with a small amount of clear acrylic solvent cement and press the frame face onto the inner circle of the acrylic face plate, being careful to line up the frame face with the boundaries of the circle and the openings in the frame face with their matching shapes on the acylic. Weight the frame in place to create pressure on the frame/acrylic join and let the adhesive cure for 18 to 24 hours. Afterwards remove the plastic layer on the outer edge of the acrylic face plate and the smaller pieces inside. It may be necessary to use tweezers to remove the inner layers.
If the frame is not well lined up with the face plate during gluing the armature may not be able to be inserted into the housing fully.
Insert the Reed switch into the space on the face of the frame (See Image 13). Attach the reed switch using two #6-32 x 1/8 inch long screws. All components installed into the 3D printed frame should be no more than finger tight to avoid damaging threaded holes or the frame. Cut the wires of the Reed switch to be about four inches long and remove the last 1/8 inch of the insulated sleeve. Attach KK crimp terminals onto the ends of the two wires and plug the wires into a 2- hole female KK connector (the order does not matter).
Insert the Reed switch into the space on the face of the frame (See Image 13). Attach the reed switch using two #6-32 1/8 inch long screws. All components installed into the 3D printed frame should be no more than finger tight to avoid damaging threaded holes or the frame. Cut the wires of the Reed switch to be about four inches long and remove the last 1/8 inch of the insulated sleeve. Attach KK crimp terminals onto the ends of the two wires and plug the wires into a 2-hole female KK connector (the order does not matter). Insert the OLED into the space in the face of the frame, taking care to orient the screen properly and making sure it sits flat in the space (See Image 14), then attach the OLED to the frame using two #2-56 x 1/8 inch long screws at opposite corners. The OLED has a glass screen which is easily cracked if tightened too much, so only screw in the screen until there is some resistance, less than hand-tight.
Use a flat edge to bend the pins of the IR sensor at a right angle to the flat back of the sensor. Clip the pins so they’re 1/3 of an inch long. Lightly coat the outside edges of the sensor in two-part epoxy and place into the IR sensor hole in the face of the frame (See Image 14). A small piece of tape can hold the sensor in place while the epoxy cures for 18-24 hours.
Install the power connection
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.
Building the circuit board
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.
Use a flat edge to bend the pins of the Mosfets at a right angle. Install the Mosfets into the top of the board and solder the pins in place (See Image 25). Flip the board over and solder the pins into place on this side as well, then, use flush cutters to remove excess pins and solder. As with all the board’s components, be careful to heat both the board and the pins to ensure a good solder connection to avoid function and conductivity issues later on.
On the bottom of the board install the header pins for the temperature breakout board. Flip the board over and solder the header pins in place. Use flush cutters to remove excess pins and solder. Flip the board back over and solder the four indicated pins of the temperature breakout board to the header pins (See Image 26). Use the flush cutters to remove any excess pins and solder.
Install the RTC coin cell battery holder into the bottom of the board. Flip over the board and solder the battery holder pins in place. The short pins of the battery holder can make it difficult to get a good solder connection between the holder and the circuit board. To verify that the solder was done properly install a coin cell battery and use a voltmeter to verify current traveling between the two newly soldered pins. The next step will cover these pins with the teensy, so it’s important to check proper installation before moving on.
Place the Teensy microcontroller in position on the pins on the top of the board and carefully solder the pins (See Image 27). Use caution not to touch any of the other components of the Teensy which might damage the function of 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:
Once the text files have been added to the microSD card it can be inserted into the slot on the Teensy.
Install the sampler code to the Teensy 3.5
Putting it all together
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).