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Sensor

This repository describes the steps needed to build a DIYSCO2 Sensor. Both, the hardware and software components are covered here. Please note that the hardware setup is subject to change and therefore the documentation will update accordingly.

Table of Contents generated with DocToc

Hardware: Build A DIYSCO2

Parts & Components

Before you start, you are going to need the following items:

  • IRGA:
    • 1 x Licor Li-820 infrared gas analyzer
  • Microcontroller System:
    • 1 x Arduino Mega microcontroller
    • 1 x Adafruit Ultimate GPS Logger Shield with GPS Module
    • 2 x Maxum Integrated One Wire Gitial Temperature Sensor DS18B20
    • 1 x Custom hardware board (contact us!)
    • 3 x LED lights
    • 1 x 8 or 16gb microSD card
    • 2 x standard A-B USB cable, for USB 1.1 or 2.0 (1 for connecting to your computer and one to modify to deliver power to arduino)
  • Custom Hardware Board:
    • 1 x DC/DC power supply (PXE30-12S12)
    • 1 x 4-pin RS232 connector (header)
    • A handful of single row Socket pins
    • A handful of 8-pin headers
    • 1 x Relay driver socket
    • 1 x resistor network
    • 1x diode (DS1)
    • 4 x resistors (2 x 10k, 2 x 5k)
    • 3 x fuses
    • 1 x LED light
    • 2 x Relays
    • 2 x capacitors
    • 1 x 7805
    • 1 x fuse holder
    • 2 x 8 position black connectors
    • 1 x UNL2803A
  • RS232- Cable (PC to Arduino)
    • 1 x Jtron Mini TTL to RS232 MAX3232
    • 1 x Connector to Arduino (Model EC100F-4-D; Newark:36B6799 )
    • Heat Shring 2.5'' ( 1/2'' FIT221 or similar)
    • 1 x Ribbon cable: 9 conductor, #28 Str., 0.05 pitch 3M 3302/9SF
    • 1 x D9F, Amphenol (Newark #99K7473 or 46F2695)
  • Inlet tube system & filter:
    • 1 x 3m long inlet tube (6.35mm diameter, Synflex, polythelene-aluminum composite)
    • 1 x KNF NMP015 microdiaphragm pump
    • 1 x Balston Disposable filter unit (DFU)
    • 1 x Swagelok needle valve
    • a handful of tube fittings (https://www.swagelok.com/en/catalog/Fittings)
  • Box container:
    • 1 x weatherproof Nanuk 910 case or equivalent
  • Power supply:
  • Additional components:
  • Other considerations:
    • Drill
    • heat gun
    • nuts and bolts
    • crimper for molex fittings and pins

Putting together your Custom Hardware Board

The custom hardware board instructions will be improved in the near future. For now, please refer to the instructions here.

Assembling the Arduino Components

Adafruit GPS

Your adafruit GPS will come with break away headers. You will need to solder the pins in order to connect it to the custom hardware board.

The diagram below shows which pins should be soldered for our use case.

Standard A-B USB cable to power the Arduino Mega

The Arduino Mega is powered by 5V which is fed in through the USB port. In order to feed power into the Arduino Mega, follow the steps below:

  1. Cut the USB cable to the X cm, keeping the side which plugs into the Arduino and discarding the other end.
  2. Strip the shrink wrapping around the cut end to expose the wires below - there should be a red and black wire.
  3. Strip the shrink wrapping around the red and the black wire

Temperature Sensors

There are 2 temperature sensors that are part of the system. One thermometer goes within the box to monitor the internal box temperature and the other thermometer goes outside next to the inlet. You will need to add wire to each temperature sensor to elongate them. The internal thermometer will be extended to ~25-30cm and the external thermometer to ~3m in length.

RS232 to Arduino Connector Cable

The instructions for creating the connector cable from the li-820 to the arduino can be found here.

Power Supply:

We rely on an input 12V power supply for the DIYSCO2 system. You may choose to power your systems however you'd like, but we suggest the following setup:

You will take your wires for your sensor and attach 2-pin molex fittings (http://cablesandconnectors.com/PIX/moljr2pin.jpg) - the male side will go on the wires attached to your DIYSCO2 and the female fittings will go to where the power is coming from.

NOTE: You will need a crimper to crimp the pins to the ends of the wires.

Inlet Tube System, Pump, & Filter

The inlet tube system is composed of a 3m long inlet tube, the balston filter, and the pump. In this section we will see how to add this to our DIYSCO2 Box.

Inlet tube:

Outlet tube:

Repeat the steps above to create an outlet tube (if desired). Our experience was that it reduced the noise generated from the pump of the sensor and also releases the samples outside of the vehicle.

Intermediate tube between inlet and filter:

Balston filter:

  • You will attach one end of the balston tube to the Pneumatic Straight Union Tube OD Push to Connect Fitting which is connected to the intermediate tube you just made above.
  • On the other end, you will attach more another Pneumatic Straight Union Tube OD Push to Connect Fitting.

Tubing from Balston Filter into the sample-in of the Li-820 irga

  • Based on the length that now exists between the filter and the sample-in of the li-820, cut a length of tube.
  • You will slip the li-820 nut over the tube and then firmly squeeze the tube over the sample-in nozzle.
  • Pull the nut over the threads of the sample-in nozzle and then tighten.

Tubing from Li-820 to pump and the outlet

  • Cut a short length of tube (~7-10cm)
  • attach one end to the in-direction (it should just slip on - careful, you don't want to break the nozzle)
  • slip a li-820 nut onto the tube faced outward
  • firmly squeeze the tube over the sample-in nose and screw the nut onto the li-820.
  • last, you will prepare a tube for the outlet of the samples.
  • First cut a tube length of the remaining distance between the outlet of the pump to the outlet of the box.
  • place a ferrule and a nut on one end and secure it to the tube.
  • connect the free end of the tube to the out-direction of the pump.

NOTE: you may use a heating gun to bend the tube so that it fits easier/nicer into the box and around the nozzles.

Wiring Everything up:

If you've made it this far, bravo! Now it's time to wire everything up (woo!). Please refer to the following diagram to see where all of the wires go.

Software: Arduino & Li-820

The DIYSCO2 Software & Arduino

Install the libraries

Install the sensor library dependencies in the Arduino/libraries directory to your machine. Follow the instructions listed here to make the libraries available on your machine.

Upload the DIYSCO2 logger program

To upload the li_820 logger program to the arduino board:

  1. open the Arduino/LI820_Logger/LI820_Logger.ino in the Arduino IDE
  2. Plug your arduino mega into the computer using the USB cable
  3. click upload

Upload Li-820 Configurations

You will need to make sure that the Li-820 has the right configurations uploaded. To do this you will need hyperterminal (only on windows)

Check your system

To check what the current config of your system - send this via hyperterminal:

  1. First: connect to the instrument (look for the little telephone icon) - you will need to connect the rs232 cable with your computer's rs232 port.

  2. Second: copy 1 of the following commands from a text editor:

     This should send you back the current configuration of your system.
 
 <LI820> <CFG> ? </CFG> </LI820>
     
 or
     
 <LI820>?</LI820>

  3. Third: edit --> paste to terminal (or something like this)

  4. Forth: get the current config of your system

Sync your system

Using hyperterminal or any other RS-232 communication program - send this config to the LI-820:

Once you know what the config is, make sure that this config is the same for all systems - particularly, be sure that the filter rate is 1 second.

  1. First: connect to the instrument (look for the little telephone icon)

  2. Second: copy 1 of the following commands from a text editor:

     <LI820>
  <CFG>
     <OUTRATE>1</OUTRATE>
     <PCOMP>TRUE</PCOMP>
     <HEATER>TRUE</HEATER>
     <FILTER>1</FILTER>
     <BENCH>14</BENCH>
     <ALARMS>
         <ENABLED>FALSE</ENABLED>
         <HIGH>900</HIGH>
         <HDEAD>-1</HDEAD>
         <LOW>300</LOW>
         <LDEAD>-1</LDEAD>
     </ALARMS>
     <DACS>
         <RANGE>5.0</RANGE>
         <D1>CO2</D1>
     </DACS>
  </CFG>
  <RS232>
      <CO2>TRUE</CO2>
      <CO2ABS>TRUE</CO2ABS>
      <CELLTEMP>TRUE</CELLTEMP>
      <CELLPRES>TRUE</CELLPRES>
      <IVOLT>TRUE</IVOLT>
      <STRIP>FALSE</STRIP>
      <ECHO>TRUE</ECHO>
      <RAW>FALSE</RAW>
  </RS232>
 </LI820>

  3. Third: edit --> paste to terminal (or something like this)

  4. Fourth: Make sure the tags = "TRUE" --> this confirms that the configuration was received and valid.

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