Jun 12, 2024

Public workspaceMaterials and assembly for a portable soil greenhouse gas flux collection case V.2

DOI
dx.doi.org/10.17504/protocols.io.dm6gp3mkpvzp/v2
  • 1University of Nebraska-Lincoln;
  • 2USDA-ARS;
  • 3USDA-ARS (retired);
  • 4formerly USDA-ARS
Marty Schmer
Open access
DOI: dx.doi.org/10.17504/protocols.io.dm6gp3mkpvzp/v2
Protocol Citation: Rachel E. Clarkson, David Walla, Robert Harrison, Myron Coleman, Marty Schmer, VIRGINIA.JIN 2024. Materials and assembly for a portable soil greenhouse gas flux collection case. protocols.io https://dx.doi.org/10.17504/protocols.io.dm6gp3mkpvzp/v2Version created by Marty Schmer
License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License,  which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: Working
We use this protocol and it's working
Created: January 11, 2024
Last Modified: June 12, 2024
Protocol Integer ID: 93382
Keywords: carbon dioxide, greenhouse gas flux, long-term agroecosystem research network, LTAR, methane, nitrous oxide, NP 216, static chamber, USDA-ARS, Agroecosystem Management Research Unit
Disclaimer
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, family status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) USDA is an equal opportunity provider and employer. Mention of commercial products and organizations in this manuscript is solely to provide specific information. It does not constitute endorsement by USDA-ARS over other products and organizations not mentioned.
Abstract
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).
Image Attribution
Rachel E. Clarkson
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.
  • The terminal strips should be tightened as much as possible at installation. Wiring should be checked each time the flux case is used.
Materials

ABCDEFG
Item NameQuantity required per caseDetailsQuantity per orderManufacturerPotential SupplierPart/Model #
8 channel relay module11Progressive AutomationsProgressive AutomationsLC-202
solenoid valve51/8 NPT Direct Acting 3 Way Solenoid Valve (12VDC DIN), 200C coil6STC (Sizto Tech Corp)STC (Sizto Tech Corp)3V1-1/8-1-D
actuator1Input Voltage: 12VDC, Full Load: 35lbs, Type of Duty:25%, Stroke: 3, Degree of Protection. IP54 1Firgelli Automations FA-35-S-12-3 (5:1)
Nylon Plastic Check Valve with Barbed Fittings (Check Valve with Barb)1Ball, 1/8 Inlet Tube ID x 1/8 NPT Male Outlet1McMaster-CarrMcMaster-Carr6079T124
Plastic Pipe Fitting for Oil, Plug with External Hex Drive Style, 10-32 UNF Male (Plug)5Plug with External Hex Drive Style, 10-32 UNF Male1McMaster-CarrMcMaster-Carr8316T33
Compact Plastic Threaded Check Valve 1/8 NPT Male X 1/8 NPT Male (Check Valve)11/8 NPT Male X 1/8 NPT Male1McMaster-CarrMcMaster-Carr1424T11
Medium-Pressure Aluminum Threaded Pipe Fitting (Straight Connector)3Straight Connector, 1/8 NPT Male1McMaster-CarrMcMaster-Carr3861T81
Plastic Quick-Turn Tube Coupling (External Quick-Turn Tube Coupling)1Plugs, for 1/8 Barbed Tube ID, Nylon10McMaster-CarrMcMaster-Carr51525K123
Plastic Barbed Tube Fitting for Air and Water (Barbed Elbow)1Tight-Seal, Elbow, 1/8 ID x 1/8 NPT Male, White10McMaster-CarrMcMaster-Carr5463K485
Plastic Quick-Turn Tube Coupling (Luer Lock Socket)4Sockets, 1/8 NPT Male, White Nylon Plastic10McMaster-CarrMcMaster-Carr51525K439
Plastic Quick-Turn Tube Coupling (Quick-Turn Tube Coupling)1Sockets, for 1/8 Barbed Tube ID, Polycarbonate10McMaster-CarrMcMaster-Carr51525K283
Rustrictor Field Box Large1Rustrictor Field Box Large- 1612; UPC: 000240990098674PlanoCaprice ElectronicsPLA1612R
30 mL Syringes4Bulk Syringes, Nonsterile225AvantorBD MedicalBD 301033
50 mL Syringe150 mL Syringe Disposable Luer Lok Sterile40Midland ScientificMidland ScientificBD 309653
14 Red Stranded CU THHN Wire (Red Stranded #14 Wire) 5 feet (approx.)Wiring for outlets, switches and other loads; copper; 14 amps max50 feetSouthwireHome Depot22957583
18 Black Solid CU TFN Fixture Wire (Black Solid #18 Wire)2 feet (approx.)#18 AWG wiring; rated 600V500 feetSouthwireHome Depot26977906
Tygon S3 Lab Tubing (Plastic Tubing)approx. 1.5 feetE-3603 1/8 x 1/4100 feetSaint-GobainMidland LabsSAINT GOBAIN ACF02007
Machine Screw: M3 Thread Size, 35 mm Lg, Steel, Zinc Plated, Pan, Phillips, Metric (Machine Screw)5 100Grainger Grainger 6GE50
Hex Nut: M3-0.50 Thread, 5.5 mm Hex Wd, 2.4 mm Hex Ht, Steel, Class 6, Zinc Plated (Hex Nut)5 100Grainger Grainger 6CA69
20cm Length Jumper Wire/Dupont Cable Multicolored (10 Color) M to F, M to M, F to F Each 40pin for Prototype Breadboard/DIY/Raspberry Pi 3, 4/Orange pi/BBC Micro: bit/Makey makey (Jump Wires)11120HaitronicAmazonX00187CA4J
DC Converter Step Down (5V 3A 15W) (Converter Box)1 1Tobsum BinzetAmazonX002EJ5Q5F
Sealed Rechargeable Battery 1DC Power: Constant Voltage Charge, Cycle Use: 14.4-15V, Standby Use: 13.5-13.8V, Initial Current: 1.5A Max 1Power Sonic (PS)AmazonPS-1250 F1. 12 Volt
Terminal Strips 8p 15a (Terminal)2 6MilaPeakAmazonX001RH1R67 Or TB1508
Rocker Switch1Rated Voltage: 12V DC, Mounting Size:20mm, Rate Current:20A, Wire Length: 200mm4ApieleAmazonKCD1-8-101NW Green Or X002U187DP
Arduino Uno Rev.3 1 1ArduinoAmazonA000066
Plug Jack to Bare Wire Open End Pigtail (a/c Adaptor)1L-Shape replacement 5.5mm x 2.1mm DC power supply repair cable, 90-degree right angle plug to bare wire open end pigtail power cord.4FancaseeAmazon
ReadyWired USB Cord Cable for Arduino UNO R3 Mega2560 Mega328 Nano (USB Type A)1USB Type A1ReadyWiredAmazon
Spade Wire Connector Electrical Crimp Terminal (Spade Connector)2Female Quick Disconnect; Insulated; 16-14 AWG 6.3mm FDD 2-250 Blue 100Baomain Electric Inc.AmazonFDD 2-250
Black Electrical Tape13/4 (W) x 66' (L); Strong Self-Adhesive Waterproof Vinyl Tape 1GTSEAmazonGTSE-ULPVC2019BLA-SL
Teflon Tapeas needed1/2 (W) x 520 (L) per 1 roll; PTFE material4 rolls VotmellAmazonVTM-V004
Velcroapprox. 1 footVelcro Brand Heavy Duty Tape; 16' (L) x 1 1/2 (W); 16'Velcro USAAmazonVEL-30838-USA
Velcro Brand One-Wrap Cable Ties 18x1/2 Black Cord Organization Straps, Thin Pre-Cut Design,100Velcro USAAmazon91140
4 Zip Ties 6Zip Ties 4-inch, Small Zip Ties with 18lb Tensile Strength200TanttiAmazon
Male to male jump wire5Red 18 AWG Jumper Lead Pin to Pin Tin 8.86 (225.00mm) 10MolexDigikey2147622123
Material list for flux case assembly

Safety warnings
Attention
Do not attach the battery until you are certain everything is correctly wired, and you are done working with exposed wiring. Attaching the battery with incorrect wiring may short circuit the Arduino Board, rendering it useless. Additionally, attaching the battery to the circuit renders everything as “live” meaning any exposed wiring could result in an electrical shock.

It is recommended that no changes are made to the provided code for the Arduino unless completely confident and familiar with coding. Changes to the provided code may cause the automated GHG case to function incorrectly.
Before start
It is recommended to read both the protocol and watch the videos prior to assembly.
Plumbing the Flux Case
Plumbing the Flux Case
Flip orientation of solenoid valves
Note
Tools required:
(2) medium-sized straight screwdrivers
(1) medium-sized Philips screwdriver
1/4 inch wrench
6 inch (150 mm) crescent/adjustable wrench
precision screwdrivers

Materials:
(5) solenoid valves
(1) check valve with barb
(5) plugs
(1) check valve
(3) straight connectors
(1) Quick-Turn tube coupling
(1) barbed elbow
(4) Luer-lock sockets
(1) external Quick-Turn tube coupling
Teflon tape

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.
Once apart from the base, remove the screw and carefully (using a small screwdriver) push the internal wiring out of the valve top.
Check the internal wiring to make sure it is well connected and tighten the internal screw using a precision screwdriver.
Rotate the top of the valve 180° and reinsert.
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.
Insert and tighten the plastic plug in all five of the solenoid valves
Cut the Teflon tape lengthwise to create two thin strips.
Wrap the Teflon tape around the plug twice and in the opposite direction than it turns into the valve (counterclockwise).
Carefully thread the plug into the hole on the valve, making sure it is inserted straight.
Use a ¼ inch wrench to carefully tighten the plug. Ensure the plug is threaded tight, but without stripping the threads on the plug.
Complete steps 2.1 through 2.4 on all five solenoid valves.
Tighten the bolt with the plastic plugs inserted into them using an adjustable wrench.
Connect the Purge and First Solenoid Valve.


First insert both long screws into the holes on the purge solenoid valve (Figure 1).
Figure 1. Part sizing for solenoid valve connection (Nut-top left; short screw-middle left; long screw-bottom left; o-ring-bottom right) Nut, screws, and o-ring are included with solenoid valve.

Flip the valve over and screw the back ends of the short screws onto the long screws (Figure 1).
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 solenoid valve.
Figure 2. Connection of purge solenoid valve to the first solenoid valve

Screw the two nuts onto the ends of the short screws through the first solenoid valve.
Tighten the screws together using 2 medium size flat head screwdrivers until the two solenoid valves are fitted tightly together.
Connect the solenoid valves together using the aluminum threaded straight connectors.
Wrap the threads twice around using Teflon tape going in the opposite direction of which the straight connector threads into.
Thread the straight connector into the right side of the first solenoid valve and tighten using a 6-inch crescent (adjustable) wrench.
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 into.
Repeat with the other two straight connectors (Figure 3).
Figure 3. Solenoid valve plumbing assembly diagram.

Connect the Nylon Check Valve to the top of purge valve (Figure 3).

Wrap the threads twice around using Teflon tape going in the opposite direction of which the check valve threads into.
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.
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.
Connect the Luer-Lock straight sockets to the top of valves 1-4 (Figure 3).
Wrap the threads twice around using Teflon tape going in the opposite direction which the Luer-lock socket threads into.
Carefully thread the Luer-Lock socket into the top hole of Valve 1 (Figure 3), making sure it is threaded in straight.
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.
Repeat steps 7.1 to 7.3 for valves 2 through 4.
Connect the check valve with hose barb to the side of the purge solenoid valve (Figure 3).
Wrap the threads twice around using Teflon tape (going in the opposite direction of which the check valve with barb threads into).
Carefully thread the check valve with hose barb into the purge valve tapped hole.
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.
Connect the barbed elbow to the side of solenoid valve 4 (Figure 3).
Wrap the threads twice around using Teflon tape going in the opposite direction of which the barbed elbow threads into.
Carefully thread the barbed elbow into the tapped hole, making sure it goes in straight.
Once the barbed elbow is threaded in, tighten it using a 6-inch crescent wrench (take caution to not over tighten and strip the threads). When finished tightening, barbed elbow should be facing towards the front of the solenoid valves (in the same direction as the Luer-Lock straight socket).
Video instruction for plumbing the flux case.
Video

Wiring the Flux Case
Wiring the Flux Case
Wiring Steps
Note
Tools required:
wire cutter
wire strippers
precision screwdrivers
medium Philips screwdriver

Materials:
Assembled solenoid valve system
(1) 8-relay module
(1) actuator
red stranded #14 wire (58.5 inches)
black solid #18 wire (16 inches)
(1) convertor box
(11) jump wires
(1) terminal and red terminal barrier strip
(1) terminal and black terminal barrier strip
(1) 12V battery
(1) rocker switch
(2) jump wires with spade connectors
(1) Arduino
(1) a/c adaptor
(2) spade connectors
(2) 4-inch zip ties
electrical tape

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)
Use the wire strippers to strip approximately 1/8 inch to 1/4 inch of the outer wire insulator, exposing the inner wire. Complete this on both sides of all the wires cut in step 11.1.
Arrange the electrical components following Figure 4.
Figure 4. Electrical component arrangement.

Connect the terminals with the terminal barrier strips.
  1. Remove the plastic cover on the terminals, then use a medium Philips screwdriver to loosen the screws on one side of the strip.
  2. On one terminal insert a red (positive) terminal barrier strip, then tighten the screws using a medium Philips screwdriver.
  3. Complete this with the other terminal strip, but instead with the black (negative) terminal barrier strip.
Wire the valves, positive (red) to positive terminal (red-PT) following the connections chart below.

ABC
Positive valve wires (red)Positive terminal (red)
Purge>>>>PT2
Valve 1>>>>PT3
Valve 2>>>>PT3
Valve 3>>>>PT4
Valve 4>>>>PT4
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.
Wire the valves, negative (black) to the relay module (Figure 5) following the connections chart below.

ABC
Negative valves wire (black)Relay module
Purge>>>>K8:2
Valve 1>>>>K4:2
Valve 2>>>>K5:2
Valve 3>>>>K6:2
Valve 4>>>>K7:2


Figure 5. Solenoid valve wiring.

Wire the actuator to the relay module following the connections chart below.
ABC
ActuatorRelay module
Positive (red)>>>>K1:2
Negative (black)>>>>K2:2

Finish wiring the relay module (Figure 6) following the connections chart below:

ABC
Relay moduleNegative terminal
K1:1>>>>NT7 (8" red wire)
Relay modulePositive terminal
K2:3>>>>PT7 (8" red wire)
Relay moduleRelay module
K1:1>>>>K2:1 (2" black wire)
K2:1>>>>K3:3 (2" black wire)
K3:3>>>>K4:3 (2" black wire)
K4:3>>>>K5:3 (2" black wire)
K5:3>>>>K6:3 (2" black wire)
K6:3>>>>K7:3 (2" black wire)
K7:3>>>>K8:3 (2" black wire)
K1:3>>>>K2:3 (2" black wire)

Figure 6. Relay module wiring

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.
Wire the converter box following the connections chart below.

ABC
Converter boxConnection
12V>>>>PT5 (8" red wire)
24V>>>>NT6 (8" red wire)
5V>>>>GND (module) jump wire
3A>>>>JD-UCC (module) jump wire

Note
Before beginning to wire the last two jump wires on the relay module, remove the cap (yellow) from the relay module.
Once all the wires are in place, use a medium Philips screwdriver to tighten down all the screws. Make sure connections are secure.
Connect the spades on the pre-soldered wires to the SW1 and SW2 positions on the rocker switch (Figure 7).
Figure 7. Rocker switch connections
Wire the rocker switch following the connection chart below.

ABCD
Rocker switchTerminalWiring
SW1>>>>Negative batteryBlue connection with spliced red stranded wire (7 inches)
SW2>>>>NT1Black connection with spliced red stranded wire (11.5 inches)
SW3 (gold connection)No connection
Securely connect a spade wire connector to the end of the red stranded wire so it can be connected to the negative battery terminal.
Wire the A/C Connector following the connections table below.

ABC
A/C connectorTerminal
Positive (red)>>>>PT1
Negative (black)>>>>NT8
The A/C connector should be negative on the outside and positive on the inside.
Wire the connections for the positive battery terminal following the connections table below.

ABC
Battery terminalPositive terminal
Positive>>>>PT8 (8.5" red wire)
Securely connect a spade wire connector to the end of the red wire for connections to the positive battery terminal.
Wire the Arduino to the relay module.
Critical
Wire the Arduino to the relay module using jump wires by following the connections table below.

ABC
ArduinoRelay module
8>>>>IN1
9>>>>IN2
2>>>>IN3
3>>>>IN4
4>>>>IN5
5>>>>IN6
6>>>>IN7
7>>>>IN8
5V>>>>UCC

Note
Make sure all connections are in the correct order listed.

Use two small zip ties to connect the plastic base of the Arduino to the Arduino board.
  1. 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.
  2. Once tight, cut off the excess zip tie ends.
Plug the A/C connector into the Arduino (Figure 8)

Figure 8. Completed wiring of the flux case.


Video instruction for wiring the flux case
Video

Connecting the Purge Syringe to the Actuator
Connecting the Purge Syringe to the Actuator
Purge syringe (50 mL) and actuator assembly
Note
Tools required:
precision screwdriver
small file
needle nose pliers

Materials required:
(5) machine screws
(5) hex nuts
(1) 50 mL syringe
(4) small zip ties
(6) 3-D printed parts (available at https://github.com/marty-schmer/flux-case-3Dparts)

Pull the plunger out of the 50mL syringe barrel and take off the rubber seal (Figure 9).
Figure 9. Syringe components.

Slide 3-D print part #3 (Figures 10, 11) onto the plunger with the ledge facing towards the plunger flange.
Figure 10. 3-D printed parts for the syringe installation on the actuator

Note

Reattach the rubber seal on the plunger and press the plunger back into the barrel of the syringe.
Attach 3-D printed part #5 (Figure 10) onto the plunger flange (Figures 11, 12). Ensure the circular flange fits into part #5.
Figure 11. Syringe plunger with 3-D printed part 3 attached.

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.
Note
Use needle nose pliers to pull the zip ties to ensure a tight fit between 3-D printed parts #3 and #5.

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.

Figure 12. 3-D printed parts #4 and #6 attached to the syringe barrel.

Note
The M3 machine screws are inserted through Part #4 and attached to the M3 hex nuts through part #6. Use a precision (small) Philips screwdriver to tighten the machine screws until the 3-D printed parts #4 and #6 do not move on the syringe.

Insert 3-D printed part #2 through the hole at the top of the actuator.
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.
Note
Using a small file, file the inside of part #2 as necessary.

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.
Configure 3-D printed part #1 so it lines up with part #4 around the actuator.
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).
Figure 13. Syringe mounted onto the actuator using 3-D part #1. Ensure there is a gap between 3-D printed parts #1 and #4 on the flat or square side of the actuator.

Note
DO NOT OVERTIGHTEN: The rounded portion ends of the 3-D printed parts #1 and #4 will end up touching, but the 3-D printed parts on the square (flat side) of the actuator should not touch. Overtightening of the 3-D parts on the square side will result in breaks to the 3-D printed material.

Flip the rocker switch to test that the mounted parts and syringe are functioning properly prior to installation in the case.
Video instructions on connecting the purge syringe to the actuator.
Video

Installation into the Case
Installation into the Case
Installation case steps.

Note
Tools Required for this Section
Philips screwdriver (medium)
Scissors
13/16 inch drill bit
1/4 inch drill bit
Drill
Materials Required for this Section
Velcro (11.25 inches)
plastic tubing (14 inches)
external quick-turn coupling
quick-turn coupling
Velcro cable ties
(4) 30 mL syringes

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.
Figure 14. Recommended 13/16 inch drill location for rocker switch.

Drill a hole on the side of the case using a 1/4 inch drill bit (Figure 15) on the low speed setting.

Figure 15. Recommended location to drill a 1/4 inch hole on the side of the case.

Disconnect the battery from the wiring circuit.
Disconnect the rocker switch electrical connection and insert into the 13/16 inch hole at the top of the case (Figure 14).
Cut Velcro (loop and hook sides) 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.

Attach the Loop (Soft) Velcro to the inside of the case (Figure 16).


Figure 16. Velcro (soft side) placement in the case.

Attach the Hook (Rough) Velcro to the back of each of the electronics as centered as possible.
Note
The Arduino, relay module, positive terminal, negative terminal, converter box, and actuator will require one 0.75 inch by 2.25 inch piece of Velcro per item.

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.
Cut plastic tubing to the following lengths.
  • Inside case tubing-5.5 inches long
  • Outside case tubing-8.5 inches long
Attach a Quick-Turn tube coupling to the end of the 5.5 inch long tubing and attach an external quick-turn tube coupling to the 8.5 inch long tubing.
Attach the end of the 5.5 inch 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.
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).
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.
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.
Lift the actuator syringe piece and screw on the Quick-Turn tube coupling connected to the 5.5 inch long tubing piece, then place the actuator back into place.
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.
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.
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.
Attach the (4) 30-mL syringes onto the Luer-Lock socket connectors located on the solenoid valves.
Note
Overtightening the Luer-Lock socket connectors can cause thread stripping.

Video instruction for component installation into the case.
Video

Adding the Flux Case Software Program to the Arduino Board
Adding the Flux Case Software Program to the Arduino Board
Program upload
Note
Tools required for this section
USB to USB Type A connection cable

Software
Software to run the flux case can be found at: https://github.com/marty-schmer/flux-case

Visit the Arduino website (https://www.arduino.cc/en/software) to download the Arduino software
Connect the computer to the Arduino board using a USB Type A connection cable.
Open the Arduino software on the computer, click on the flux case program file, choose the program, and open it.

Note
Flux case software can be found at: https://github.com/marty-schmer/flux-case

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.
Once the software program is successfully transferred, disconnect the USB Type A connection cable from the Arduino board.
This completes the assembly of the automated flux case.
Please check for stranded wires prior to initiating the flux case.
Protocol references
Arnold, S. L., Parkin, T. B., Doran, J. W., Eghball, B., & Mosier, A. R. (2001). Automated Gas Sampling System for Laboratory Analysis of CH 4 and N 2 O †. Communications in Soil Science and Plant Analysis, 32(17–18), 2795–2807. https://doi.org/10.1081/CSS-120000962

Davis, M. P., Groh, T. A., Parkin, T. B., Williams, R. J., Isenhart, T. M., & Hofmockel, K. S. (2018). Portable Automation of Static Chamber Sample Collection for Quantifying Soil Gas Flux. Journal of Environmental Quality, 47(2), 270–275. https://doi.org/10.2134/jeq2017.10.0387