TITLE: Materials and assembly for a portable soil greenhouse gas flux collection case
AUTHORS: Rachel E. Clarkson, David Walla, Robert Harrison, Myron Coleman, Marty Schmer, VIRGINIA.JIN

[DESCRIPTION]
The collection of soil nitrous oxide, carbon dioxide, and methane greenhouse gas (GHG) flux measurements utilizing static chamber sampling methodology can be both time and labor intensive.  The development of an automated field sampling system would allow for the collection of soil GHG samples from multiple static chamber sites more quickly and efficiently (Arnold et al., 2001).  This document describes the material assembly of a modified version of the Chamber Automated Sampling Equipment (FluxCASE) from Davis et al., 2018.  This automated GHG case is compatible with existing soil GHG static hoods and requires minimal field training to use.  The automated GHG case main components are: one 12-volt marine battery, five solenoid valves with attached syringes, a microcontroller, and an actuator.  Estimated materials costs for assembly and building one automated GHG case is approximately $600.00 (2024 dollars).

[BEFORE_START]
It is recommended to read both the protocol and watch the videos prior to assembly.

[GUIDELINES]
Manufacturing of 3-D printed parts are required for the actuator assembly.
3-D materials used may affect the durability of the purge syringe with the actuator.
We recommend using pre-cut jump wires rather than spools of wire to save time.

[STEPS]
SECTION: Plumbing the Flux Case
1. Flip orientation of solenoid valves
 

SECTION: Plumbing the Flux Case
2. Insert and tighten the plastic plug in all five of the solenoid valves
2.1. Cut the Teflon tape in half lengthwise to create two thin strips.
SECTION: Plumbing the Flux Case
1.1. Remove the top screw from the solenoid valve using a medium Philips screwdriver, then carefully unplug the top wired portion making sure to keep the internal wiring tucked inside.
SECTION: Plumbing the Flux Case
1.2. Once apart from the base, remove the screw and carefully using a small screwdriver push the internal wiring slightly out of the valve top.
SECTION: Plumbing the Flux Case
1.3. Check the internal wiring to make sure it is well connected and tighten the internal screw.
SECTION: Plumbing the Flux Case
1.4. Rotate the top of the valve 180° and reinsert.  
SECTION: Plumbing the Flux Case
1.5. Rotation of the top valve will allow for the head to be reinstalled onto the valve in the opposite direction. Reinsert the screw and tighten with medium Philips screwdriver.
2.2. Wrap the Teflon tape around the plug twice in the opposite direction than it turns
into the valve (counterclockwise).
2.3. Carefully thread the plug into the hole on the valve, making sure it is inserted
straight.
2.4. Use a ¼ inch wrench to carefully tighten the plug, making sure it is tight, but without
stripping the threads on the plug.
2.5. Complete this on all five solenoid valves
3. Tighten the bolt with the plastic plugs inserted into them using an adjustable wrench until tight.
4. Connect the Purge and First Solenoid Valve.


4.1. First insert both long screws into the holes on the purge solenoid valve (Figure 1).
 

4.2. Flip the valve over and screw the back ends of the short screws onto the long screws (Figure 1).
4.3. Place the rubber o-ring in the larger opening of the solenoid valve (Figure 2) and then carefully place the first solenoid valve over the purge making sure to guide the screws through the holes on the first.
 

4.4. Screw the two nuts onto the ends of the short screws through the first solenoid valve.
4.5. Tighten the screws together using 2 medium size flat head screwdrivers until the two solenoid valves are fitted tightly together.
5. Connect the solenoid valves together using the aluminum threaded straight connectors.
5.1. Wrap the threads twice around using Teflon tape going the opposite direction of which the straight connector threads in.
5.2. Thread the straight connector into the right side of the first solenoid valve and tighten using a 6” crescent (adjustable) wrench.
5.3. Wrap the threads twice on the other end of the straight connector with Teflon tape going the opposite direction of which the straight connector threads in.
5.4. Thread the straight connector into the left side of the second solenoid valve and tighten it down, making sure the first and second solenoid valves are as straight as possible with each other.
6. Connect the Nylon Check Valve to the top of purge valve (Figure 3).

5.5. Repeat with the other two straight connectors (Figure 3).

 

6.1. Wrap the threads twice around using Teflon tape going in the opposite direction of which the check valve threads into.
6.2. Carefully thread the solid portion of the nylon check valve into the top tapped hole of the purge valve, making sure to thread straight into the purge valve.
6.3. Once the check valve is threaded into the top of the purge valve, tighten the check valve using a 6 inch crescent wrench taking caution to not over tighten and strip the plastic threads.
7. Connect the Luer-Lock straight sockets to the top of valves 1-4 (Figure 3). 
7.1. Wrap the threads twice around using Teflon tape going in the opposite direction which the Luer-lock socket threads in.
7.2. Carefully thread the Luer-lock socket into the top hole of Valve 1 (Figure 3), making sure it is threaded in straight.
7.3. Once the Luer-lock socket is threaded in, tighten it using a 6 inch crescent wrench, taking caution to not over tighten and strip the threads.
7.4. Repeat steps 7.1 to 7.3 for valves 2 through 4.
8. Connect the check valve with hose barb to the side of the purge solenoid valve (Figure 3).
8.1. Wrap the threads twice around using Teflon tape (going in the opposite direction of
which the check valve with barb threads into).
8.2. Carefully thread the check valve with hose barb into the purge valve tapped hole.
8.3. Once the check valve with hose barb is threaded in, tighten it using a 6 inch crescent wrench taking caution to not over tighten and strip the plastic threads.
9. Connect the barbed elbow to the side of solenoid valve 4 (Figure 3).
9.1. Wrap the threads twice around using Teflon tape going in the opposite direction of
which the barbed elbow threads into.
9.2. Carefully thread the barbed elbow into the tapped hole, making sure it goes in straight.
9.3. Once the barbed elbow is threaded in, tighten it using a 6” crescent wrench taking caution to not over tighten and strip the threads. When finished tightening, barbed elbow should be facing towards the back of the solenoid valves (away from from the Luer-Lock straight socket).
10. Video instruction for plumbing the flux case.

 

SECTION: Wiring the Flux Case
11. Wiring Steps
 

SECTION: Wiring the Flux Case
11.1. Cut the following wires to the designated length:
8-2 inch long black wire (solid copper #18)
4-8 inch long red wire (stranded #14 ANG)
1-8.5 inch long red wire (stranded #14 ANG)
1-7 inch long red wire (stranded #14 ANG)
1-11.5 inch long red wire (stranded #14 ANG)
SECTION: Wiring the Flux Case
11.2. Use the wire strippers to strip approximately 1/8” to 1/4” of the outer wire
insulator, exposing the inner wire. Complete this on both sides of all the wires cut in step 11.1.
SECTION: Wiring the Flux Case
11.3. Arrange the electrical components following Figure 4.  
 

SECTION: Wiring the Flux Case
11.4. Connect the terminals with the terminal barrier strips.
Remove the plastic cover on the terminals, then use a medium Philips screwdriver to
loosen the screws on one side of the strip. 
On one terminal insert a red (positive) terminal barrier strip, then tighten the screws using a medium Philips screwdriver.
Complete this with the other terminal strip, but instead with the black (negative)
terminal barrier strip.

SECTION: Wiring the Flux Case
11.5. Wire the valves, positive (red) to positive terminal (red-PT) following the connections chart below.

 
Once the wires are in place, tighten down the screws in the positive terminal using a medium Phillips screwdriver. Make sure the wired connections are secure.
SECTION: Wiring the Flux Case
11.6. Wire the valves, negative (black) to the relay module (Figure 5) following the connections chart below. 

 

 

SECTION: Wiring the Flux Case
11.7. Wire the actuator to the relay module following the connections chart below. 
 
 



SECTION: Wiring the Flux Case
11.8. Finish wiring the relay module (Figure 6) following the connections chart below: 

 

 

    Once all the wires are in place use a precision screwdriver with a Philips head to tighten down all the screws in the relay module.  Make sure the wired connections are tight and secure. Additionally, use a medium Philips screwdriver to tighten the screws in NT7 and PT7.
SECTION: Wiring the Flux Case
11.9. Wire the converter box following the connections chart below. 

 

 
Once all the wires are in place, use a medium Philips screwdriver to tighten down all the screws.  Make sure the connections are secure.
SECTION: Wiring the Flux Case
11.10. Connect the spades on the pre-soldered wires to the SW1 and SW2 positions on the rocker switch (Figure 7).
 
Wire the rocker switch following the connection chart below.

 
Securely connect a spade wire connector to the end of the red stranded wire so it can be connected to the negative battery terminal.
SECTION: Wiring the Flux Case
11.11. Wire the A/C Connector following the connections table below. 

 
The A/C connector should be negative on the outside and positive on the inside.
13. Video instruction for wiring the flux case.
 

SECTION: Connecting the Purge Syringe to the Actuator
14. Purge syringe (50 mL) and actuator assembly
 
    
SECTION: Wiring the Flux Case
11.12. Wire the connections for the positive battery terminal following the connections table below.

 
Securely connect a spade wire connector to the end of the red wire for connections to the positive battery terminal.
12. Wire the Arduino to the relay module.
12.1. Wire the Arduino to the relay module using jump wires by following the connections table below.

 

 

12.2. Use two small zip ties to connect the plastic base of the Arduino to the Arduino board.
Thread the zip ties through the base and tighten so that the head of the zip tie is located on the top of the Arduino.
Once tight, cut off the excess zip tie ends.
12.3. Plug the A/C connector into the Arduino (Figure 8)
 

12.4. Connect to the 12V battery
Once all the connections and double checked and correct connect the positive connection to the positive end of the battery and the negative connection to the negative end of the battery. 
SECTION: Connecting the Purge Syringe to the Actuator
14.1. Pull the plunger out of the 50mL syringe barrel and take off the rubber seal (Figure 9). 
 

SECTION: Connecting the Purge Syringe to the Actuator
14.2. Slide 3-D print part #3 (Figures 10, 11) onto the plunger with the ledge facing towards the plunger flange. 
 

SECTION: Connecting the Purge Syringe to the Actuator
14.3. Reattach the rubber seal on the plunger and press the plunger back into the barrel of the syringe.
SECTION: Connecting the Purge Syringe to the Actuator
14.4. Attach 3-D printed part #5 (Figure 10) onto the plunger flange (Figures 11, 12).  Ensure the circular flange fits into part #5.
 

SECTION: Connecting the Purge Syringe to the Actuator
14.5. Use small zip ties to secure 3-D printed parts #3 and #5 together over the plunger flange.  Insert the zip ties through part #3 out of part #5 and be sure to orient the zip ties in different directions so
pieces are pulled together equally in all directions. 
 

SECTION: Connecting the Purge Syringe to the Actuator
14.6. Attach 3-D printed part #4 and #6 around the syringe, making certain the syringe barrel numbers are
facing toward 3-D part 6 (Figure 12). Use (2) M3 machine screws and (2) M3 hex nuts to secure 3-D printed parts #4 and #6 together.

 


 

SECTION: Connecting the Purge Syringe to the Actuator
14.7. Insert 3-D printed part #2 through the hole at the top of the actuator.
SECTION: Connecting the Purge Syringe to the Actuator
14.8. Fit 3-D printed part #3 over the actuator facing the syringe so it lays over the actuator. Push part #3 down until the lines in the part line up with the holes on part #2. 
 

SECTION: Connecting the Purge Syringe to the Actuator
14.9. Insert one M3 machine screw through the smooth hole and one M3 hex nut through the opposite end (hexagonal hole shape) and tighten with a precision Philips screwdriver.
SECTION: Connecting the Purge Syringe to the Actuator
14.10. Configure 3-D printed part #1 so it lines up with part #4 around the actuator.
SECTION: Connecting the Purge Syringe to the Actuator
14.11. Insert (2) M3 machine screws through the smooth holes and (2) M3 hex nuts on the opposite side and tighten using a precision Philips screwdriver (Figure 13). 
 

 

SECTION: Connecting the Purge Syringe to the Actuator
15. Flip the rocker switch to test that the mounted parts and syringe are functioning properly prior to installation in the case.
SECTION: Installation into the Case
17. Installation case steps.

 

SECTION: Connecting the Purge Syringe to the Actuator
16. Video instructions on connecting the purge syringe to the actuator.
 

SECTION: Installation into the Case
17.1. Drill a hole in the lid of the case on the side of the case with the hinges using the 13/16 inch drill bit (Figure 14) for rocker switch placement.
 

SECTION: Installation into the Case
17.2. Drill a hole on the side of the case using a 1/4 inch drill bit (Figure 15). 
 

SECTION: Installation into the Case
17.3. Disconnect the battery from the wiring circuit.
SECTION: Installation into the Case
17.4. Disconnect the rocker switch electrical connection and insert into the 13/16 inch hole at the top of the case (Figure 14). 
SECTION: Installation into the Case
17.5. Cut Velcro to the following lengths:
(6)-0.75 inch wide by 2.25 inch long pieces.
(2)-1.5 inch wide by 2.25 inch long pieces.

SECTION: Installation into the Case
17.6. Attach the Loop (Soft) Velcro to the inside of the case (Figure 16).  
 

 

SECTION: Installation into the Case
17.7. Attach the Hook (Rough) Velcro to the back of each of the electronics as centered as possible. 
 

SECTION: Installation into the Case
17.8. The battery will be situated in the corner of the box below the 13/16” hole with the prongs facing into the middle of the case.  It will have Velcro on one side of the battery and on the bottom (1.5 inch by 2.25 inch Velcro size). See Figure 16.
SECTION: Installation into the Case
17.9. Cut plastic tubing to the following lengths.
Inside case tubing-8 inches long
Outside case tubing-8.5 inches long
SECTION: Installation into the Case
17.10. Attach a Quick-Turn tube coupling to the end of the 8 inch long tubing and attach an external quick-turn tube coupling to the 8.5 inch long tubing.
SECTION: Installation into the Case
17.11. Attach the end of the 8” tubing without the Quick-Turn coupling to the barbed elbow by pushing it onto the barb until the end of the tubing is flush with the back of the fitting.
SECTION: Installation into the Case
17.12. From the outside of the case, insert the 8.5 inch piece of tubing without the Quick-Turn coupling through the 1/4 inch hole on the side of the case (Step 17.2).
SECTION: Installation into the Case
17.13. Place the circuit assembly and solenoid valve assembly into the case and position it with the proper piece of Velcro it is meant to line up with (Figure 16).  Additionally, make sure the solenoid valve assembly is positioned that the check valve with barb is aligned with the plastic tubing located in the 1/4 inch drill hole.
SECTION: Installation into the Case
17.14. Push the check valve with barb into the plastic tubing (8.5 inch plastic tubing) so that it is flush with the back of the fitting. Align the check valve with barb so that it is located on the outside of the box through the 1/4 inch hole.
SECTION: Installation into the Case
17.15. Lift the actuator syringe piece and screw on the Quick-Turn tube coupling connected to the 8 inch long tubing piece, then place the actuator back into place.
SECTION: Installation into the Case
17.16. Reattach the rocker switch wires to the circuit, making sure to tighten down the screws as much as possible to hold the wires in place.
SECTION: Installation into the Case
17.17. Use a Velcro cable tie to wrap around the last straight connector on the solenoid valves then through the hole on the outside of the case and back over the Velcro to secure it in place.
SECTION: Installation into the Case
17.18. Place the battery into the case and attach the positive spade connector to the positive terminal of the battery and the negative spade connector to the negative terminal of the battery.
SECTION: Installation into the Case
18. Video instruction for installation into the case.
 

SECTION: Adding the Flux Case Software Program to the Arduino Board
19. Program upload
 

SECTION: Installation into the Case
17.19. Attach the (4) 30-mL syringes onto the Luer-Lock socket connectors located on the solenoid valves.
 

SECTION: Adding the Flux Case Software Program to the Arduino Board
19.1. Visit the Arduino website (https://www.arduino.cc/en/software) to download the Arduino software (2.1.0 or 2.1.1).
 


SECTION: Adding the Flux Case Software Program to the Arduino Board
19.2. Connect the computer to the Arduino board using a USB Type A connection cable.
SECTION: Adding the Flux Case Software Program to the Arduino Board
19.3. Pull up the Arduino software on the computer, click on the flux case program file, choose the program, and open it.
SECTION: Adding the Flux Case Software Program to the Arduino Board
19.4. Once the flux case program is opened in the software, click the arrow button at the top left of the screen to transfer the program to the Arduino board.
SECTION: Adding the Flux Case Software Program to the Arduino Board
19.5. Once the software program is successfully transferred, disconnect the USB Type A connection cable from the Arduino board.