WatsOn

This page contains technical details and construction manuals for our measurement device WatsOn. For more details, please click on the respective tile.

Software

The software consists of several parts which provide a user interface and manage the connection to the hardware.

Different components of the software:

• GUI(graphical user interface): with the graphical interface the user can take images and time lapse of the chips in the device. The software is written in C++. It makes use of the Qt-Library[http://qt-project.org/] to provide a clear interface and a comfortable way to manage various software aspects such as handling images and establishing network connections. An advantage resulting from the utilization of Qt-Library is the multi-platform support for Windows, MacOS and Linux. Additionally Qt is available with an Open-source license which can be used for free. The software can be used locally on the Raspberry Pi or remotely from a device in the same network.
• Features:
  • change settings:
    • the user can specify the iso-value and the shutter speed of the camera
    • custom settings can be labeled and saved for future usage
    • existing settings can be updated or deleted unless they are no default configurations
    • the excitation of the LEDs for GFP(480nm) and iLOV(450nm) can be selected
  • take image/s:
    • the GUI offers two possibilities to take images:
      • take single image with the active camera setting
      • take time lapse shootings with the active camera settings and the specified interval. When activated the images are saved automatically to a user defined directory with ascending filenames
    • the last image which was taken by the camera is shown in the GUI, information containing the timestamp and used camera settings are displayed next to the image. Previous images can be selected with the arrow buttons.
  • analyse image
    • the image is analysed by an image segmentation algorithm and shows whether the pathogen Pseudomonas aeruginosa is present on the chip or not

• Backend: The backend is a software that runs on the Raspberry Pi and is responsible for the connection between the GUI and the hardware. If the user interface is executed on another device e.g. a notebook it has to be in the same network as the Raspberry Pi. The backend works like a webserver that receives commands and acts corresponding to the submitted parameters. It can take images and returns them to the GUI.

Before an image is taken the backend turns on the specified LEDs by sending a command to the connected Arduino board. Afterwards the LEDs are turned off using the same mechanism. These steps are repeated in the given interval for a time lapse shooting.

Hardware

Hardware components

• Raspberry Pi : The Raspberry Pi is a small single-board computer which runs a Linux operating system from an inserted SD-card. The steps which are required to have a fully working system are described here[###]. The main purpose of the Raspberry Pi is to run the software described above, control the attached camera and to present the GUI on the display. The big advantage of this board is that it is very powerful for its size and cheap but perfectly fits our needs.

• Raspberry Pi camera: The camera is directly connected to the Raspberry Pi board and takes the images of the chips.

• Arduino: The arduino board sets the current and thus the temperature of the Peltier heater by evaluating the received values from the temperature sensors for the interior and the aluminium block. Additionally it receives commands from the Raspberry Pi to turn the LEDs on and off.

• Relay: The 2-channel relay works like two light switches which either are turned on or off and control the 480nm LEDs or 450nm LEDs. The channels are connected and turned on and off by the arduino board.

• Peltier heater: A Peltier component transform an applied current to a hot surface on one site of the heater. To incubate the sensing cells at 37°C the arduino receives the temperatur of the temperature sensors on the aluminium block and in the interior. Then it controls the Peltier to get the desired temperature.

• Display: The display is connected to the arduino board and shows the current interior temperature

• Filter slides: To block the light that is emitted from the LEDs a filter slide is placed in front of the camera. The characteristic of the filter slide is selected depending on the frequency of the LEDs which are either 480 or 450nm ones. We used the filter '010 Medium Yellow' for the 480nm LEDs and '505 Sally Green' for the 450nm LEDs.

DIY: How To Build Your Own WatsOn

If you want to create your own WatsOn first take a look at the following list of necessary components. All parts except the laser cutted acrylic glass only need to be bought.

You can find more economical information for WatsOn and the project on our Economical View page.

Wiring of our device

	Start building your own WatsOn by assembling the base plate, the sides and the interior wall.
	Fix the Peltier heater on the back of the aluminum block and place it in the hole of the interior wall. Arrange the 4x4 450nm LEDs and the 2x3 480nm LEDs
	Assemble the camera holder with the camera and the corresponding filter slide on the lower part. Over the camera you can place the temperature sensor for measuring the indoor temperature. Finally put the fan on the back of the camera holder.
	Connect the electronic components on the outside and the inside according to the wiring diagramm.
	Put together the drawer.
	Position the front panel and insert the drawer.
	Place the temperature sensor for the aluminium block temperature directly on the block and put the back panel in front of it.
	Setup the power supply and connect all devices to either 5V or 12V.
	Mount the device on top of the power supply casing. Add the display and apply some stickers to enjoy your custom-made WatsOn.