Setup

To get the Mobile Measurement System up and running you need to install its software and to connect the measurement equipment. First you need to get the software up an running.

Software installation

System architectures

  • linux/386

  • linux/amd64

  • linux/arm/v6

  • linux/arm/v7

  • linux/arm64

Installation

Prepare your system

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install docker docker-compose git -qq -y
sudo addgroup docker
sudo usermod -aG docker $USER
sudo service docker start
sudo systemctl enable docker

Note

On some systems docker might not be available in the standard distribution repositories. Check the internet for guidance!

Copy the code base

git clone https://gitlab.dlr.de/as-boa/mobile-measurement-system.git

If you are planing to use I²C oder SPI sensors (standard use case) you need to register FTDI udev-rules

cd mobile-measurement-system/setup
bash ./install_usb.sh

Download and start the container stack:

cd ..
sudo docker-compose up -d

As a sanity check make sure four containers with an identifier MMS_* are up and running (no restarting)

sudo docker ps

This should look similar to:

[...]   IMAGE                              [...]   STATUS         PORTS                                       NAMES
[...]   nginx:1.17                         [...]   Up 1 second    0.0.0.0:80->80/tcp, :::80->80/tcp           MMS_NGINX
[...]   niehaus/mms:latest                 [...]   Up 1 second                                                MMS_SENSOR
[...]   niehaus/mms:latest                 [...]   Up 2 seconds   0.0.0.0:8000->8000/tcp, :::8000->8000/tcp   MMS_GUI
[...]   timescale/timescaledb:1.7.4-pg12   [...]   Up 3 seconds   0.0.0.0:5432->5432/tcp, :::5432->5432/tcp   MMS_DB

The MMS is installed now and can be accessed on the hosting machine via the browser using http://localhost or via other devices on the network via http://<host-ip>/. Please refer to the user manual for operating instructions. Sensor datasheets can be found in the documentation section of the web interface or the hardware description of this documentation.

Software update

To specify the new software version change the MMS_VERSION variable in your .env file to equal your desired version. Use the latest tag to refer to the most recent stable release associated to the main-Branch. Use the dev tag to get the current devolopment version. An overview of all release tags can be found on Docker Hub Registry. If you want to ensure consistency or to avoid incompatiblity issues due to i.e. api-deprecations make sure not to use latest and pin the version instead.

Online systems

Updating a mobile measurement system with access to the internet to a new release via:

cd <directory of docker-compose.yml>
docker-compose pull
docker-compose up -d

Note

When using shared IP adresses you might be prompted that your docker quota is exceeded. Workaround: Signup at Docker Hub and after confirming your account run docker login in your terminal and enter your credentials. You now have a personal quota.

Offline systems

Switch to an online system download the desired docker image. Note that you need docker on that online system to be installed, too. For downloading the image use

docker pull niehaus/mms:<version>

where <version> shall be replaced with your intended version tag.

Consequently, you need to save the image to file

docker save -o mmsOfflineImage.img niehaus/mms:<version>

Now transfer the file to your offline system and load the image

docker load -i mmsOfflineImage.img

Update MMS_VERSION in the .env file on your offline system and run the update

docker-compose up -d
docker-compose restart

Uninstall

Stop all container and remove

docker-compose rm -vfs

Remove unused volumes

docker volume prune

Delete /var/lib/mms via

sudo rm -rf /var/lib/mms

Troubleshooting

Use docker ps to check if all containers are running. If a container keeps restarting check out the

docker logs <CONTAINER NAME>

For the container responsible for reading data from measurement devices use

docker logs MMS_SENSOR

To navigate inside a running container and to execute commands from within use

docker run -it --net=mms2_default --privileged <CONTAINER NAME> bash

Raspberry Pis

Control buttons

Buttons to initialize a sensor search and to start/stop a measurement are supported using its GPIOs. Further LEDs are used to indicate a successful initialization and an ongoing measurement. The corresponding container can be installed via To add LED support an additional container needs to be registered:

docker-compose -f docker-compose.yml -f docker-compose-pi.yml

The pins are identical throughout all Pi versions. If the use of buttons is activated, buttons have to be connected.

  • The initialization button has to be connected to GPIO 7 and GND.

  • The measurement button has to be connected to GPIO 27 and GND.

LED indicators are all optional.

  • The init indicator has to be wired to GPIO 7 and GND.

  • The measurement indicator has to be connected to GPIO 10 and GND.

To start the initialization process, push the initialization button. The initialization indicator will start to blink (1/2Hz). When the initialization process has finished successfully, the blinking stops and the initialization LED is continuously active. To start a measurement, the initialization process has to be finished. If a measurement is ready to be started, the measurement LED is active. After pushing the measurement button the measurement starts and the measurement indicator will blink (1/2Hz). To stop a measurement, push the button again. The blinking will stop and the measurement ends. During measurements the initialization button is deactivated. Vice versa the measurement button is deactivated when the system performs an initialization. The web interface reflects all state changes evoked by the push buttons. Measurements are labeled according to the system time and can be found in the ‘Data’ tab of the ‘Settings’ menu.

When using a RPi 4 make sure to add proper pull up resistors to both buttons.

Wifi Client

A wifi access point for Raspberry Pis can be installed on the system level using the installation script in the setup directory setup/install_pi_ap.sh. Default parameters:

  • Gateway/Device IP: 192.168.4.1

  • SSID: YOUR_SSID

  • Password: YOUR_SECURE_PASSWORD

  • max. 20 dhcp clients

To alter these settings modify

  • hostapd configuration file at setup/setup_files/hostapd.conf

  • name server configuration at setup/setup_files/dnsmasq.conf

  • network translation at setup/setup_files/nat_config.conf

Also usefull

After cloning images shrink using:

https://github.com/Drewsif/PiShrink

Hardware

A list of supported devices and where they can be ordered is presented in the following

Sensors

A full list is included in the featured sensor section. The following subset can be ordered directly of the shelf.

Sensor type

Quantities

Supplier

Article Number

Note

SHT 85

Temperature

Digi Key

1649-1110-ND

Humidity

SFM3000

Volume flow

Mouser

403-SFM3000-200C

add socket cap

SFM3200

Volume flow

Mouser

403-SFM3200-AW

add socket cap

SFM3300

Volume flow

Mouser

403-SFM3300-AW

add socket cap

SFM4100

Volume flow

Mouser

403-SFM4100AIR

SFM4200

Volume flow

Mouser

403-SFM4200AIR

SDP810 (125Pa)

Differential pressure

Digi Key

1649-1073-ND

add socket cap

Temperature

SDP810 (500Pa)

Differential pressure

Digi Key

1649-1074-ND

add socket cap

Temperature

BME280

Absolute pressure

Digi Key

1568-1706-ND

Qwiic compatible

Temperature

Humidity

MAX31865

Temperatue

Digi Key

1528-1804-ND

Add 4-Wire PT100 RTD

SCD30

CO2 concentration

Digi Key

1649-1098-ND

Temperature

Humidity

SCD41

CO2 concentration

Digi Key

1649-SEK-SCD41-SENSOR-ND

Temperature

Humidity

SMGAir 2

Volume flow

Ingenieurs Büro Peter Stehle

Temperature

Abs. pressure

S8000

Dewpoint

Michell Instruments

Temperature

ADS1015

Voltage

Mouser

474-DEV-15334

NAU 7802

Bridge Sensor

Mouser

474-SEN-15242

SPS30

Particle matter sensor

Mouser

403-SPS30

Periphery

To connect I2C to the Host devices USB port a FTDI232 is used in combination with an I2C multiplexer to allow for identical sensor types on the same I2C bus. Bill of materials (1 mux box):

Part

Supplier

ID

Note

FT232H

Digi Key

1528-1449-ND

Any breakout board will work

BOB-16784

Digi Key

1568-BOB-16784-ND

All TCA9548A boards will work

Qwiic Cable to Wire

Digi Key

1568-PRT-17260-ND

Cut in half and solder to FTDI232 Breakout board

Note

In the future a PCB with FTDI and TCA9548A would make manual soldering obsolete and would reduce its dimensions.

Cables

In general it is adviced to keep cable connections as short as possible to reduce the risk of electromagnetic interferences (EMI). Further it is adviced to favor longer USB cables over long I2C cables. Cables that were used successfully:

Part

Supplier

ID

Qwiic - Qwiic 500mm

Digi key

1568-1713-ND

Qwiic - Qwiic 100mm

Digi key

1528-4210-ND

SHT85 - Qwiic

ESTO

custom made

SFM/SDP - Qwiic

ESTO

custom made

Raspberry Pi

Base parts

Note

Supplier

Order ID

Raspberry Pi 4

min. 4GB

Digi Key

1690-RASPBERRYPI4B/4GB-ND

5V power supply

Digi Key

1690-RPIUSB-CPOWERSUPPLYBLACKEU-ND

Case (Din-Rail)

Digi Key

1778-DINH03-ND

Real Time Clock

Digi Key

1597-1391-ND

LED-Button

red

Conrad

4016139335087

LED-Button

green

Conrad

4016139335148

Set FTDI Identifiers

If you are planing to use FT232 USB to I2C/SPI converters you need to assign unique device identifiers. This is well documented in the pyFTDI project. An example script can be found in the pyserialsensor subproject which is responsible for the sensor communication.

Minimum working examples

In the following the minimal working example for different interfaces is described

UART

Material:
Steps:

  1. Connect to the host device by entering its network address in the web browser of a device within the same local network.

  2. Connect the SPS30 to the host device. The number of COM-ports in the interface footer should increment.

  3. Navigate to the setup menu and click the yellow button in the center to start an initialization process. After completion the sensor should be recognized and a green start button on the top right of the header menu should be visible.

  4. Click on the start button. It should switch to a red stop button and a red Live menu entry should appear in the header menu.

  5. The live menu displays current measurement values. If you want to see a visualization of the measurement values, navigate to the visualization menu.

I2C

Material:
Wiring:

  • SDA: Connect D1 and D2 to the blue wire (Data in and Data out)

  • SCL: Connect D0 to the yellow wire (Clock)

  • Vin: Connect 5V to the red wire (supply voltage)

  • GND: Connect GND to the red wire

  • Connect D0 and D7 (clock stretch)

  • If you are not using a Sparkfun TCA9548 breakout board connect D0 and 5V with a 4.7kOhm resistor and D1 and 5V with a 4.7kOhm resistor

Pt100 breakout boxes

This projects supports the use of 4-wire Pt100 RTD probes. The measurement of the sensor resistance together with a analog to digital conversion is done on a MAX31865 IC and is evaluated via SPI. There are two different implementations supported by the mobile measurement system.

  • up to 5 Pt100 using one GPIO per MAX31865 as channel select

  • up to 16 Pt100 using channel select multiplexing (via CD74HC4067M)

You can either use only 5 channel versions or 16 channel pcb versions of the breakout boxes simultaneously.

5 channel Pt100 box

This can be set up easily on a breadboard for quick testing purposes. For a more reliable version use the 16 channel version.

Bill of Materials

Wiring

  • D0 pin of the FT232H to each CLK of the MAX31865 breakout board.

  • D1 pin of the FT232H to each SDI of the MAX31865 breakout board.

  • D2 pin of the FT232H to each SDO of the MAX31865 breakout board.

  • For each MAX31865 connect CS to one of the D3 to D7 pin of the FT232H

  • For each MAX31865 connect F- and RTD- to one side of the 4-wire Pt100 and F+ and RTD+ to the other.

In Settings/General select SPI mode GPIO to indicate you are using the 5 channel version.

16 channel Pt100 box

_images/max31865_16_pt100_front.png

The layout of the PCB, the KiCAD project and the gerber-export can be found here.

Bill of Materials

  • Multiplexer CD74HC4067M

  • Pt100 transducer MAX31865xAP

  • Capacitor CAP CER 0.1UF 50V X7R 0805

  • FERRITE BEAD 120 OHM 0805 1LN

  • Reference resistor (for Pt100) ERA-6AEB431V - RES 430 OHM 0.1% 1/8W 0805

  • Resistor RES 10K OHM 1% 1/4W 0805

  • Conn_01x12_Female

  • PIN - Socket B4B-ZR(LF)(SN)

Wiring

Solder a pin row to each side of an upside down Adafruit FT232H breakout board. Plug the FT232H into the socket rows of the PCB. Make sure to connect the correct pins (12 Pins on the socket and 11 pins on the the Adafruit FT232H) and double check if GND matches GND and 3.3V matches 3.3V on the FT232H.

Next you need to connect the 4-wire Pt100 to the board. For each channel connect pins 1+3 to one side of the Pt100 and 2+4 to the other. You can use JST PHR Female 2mm, 4-pin 1 row (RS Components, Farnell, DigiKey) with self or pre-crimped wires.

A layout of a breakout box can be found here. The boxes can be built using the following parts