The purpose of the project is to monitor the effort, stress, panic or myocardial predecessor moments based on impedance of skin. Taking the impedance of skin we can interpret the variation of this in time. We know the impedance of skin is inversely with effort or sickness. Also the project can be use like lie detector as well.
The graphics and impedance variation will be taken by a data acquisition system which will deliver the information to a processing system. All these data will be saved on a SD card to be interpreted.
Step 1: Bill of Materials
1 x ChipKit Cmod from Digilent
1 x Digilent PmodIA
2 x Digilent PmodRF2
1 x Digilent PmodOLED
1 x Zybo FPGA
1 x SHT 25
1 x Impedance sensors
1 x LiPo battery
1 x charger
Step 2: Wireless Sensor Node (bracelet)
The bracelet is used to keep together all the elements of data acquisition system necessary for impedance sampling. Also this keeps impedance sensor fixed on skin. We put on this bracelet the impedance sensor, ChipKit Cmod, PmodIA, PmodRF2, Temperature and Humidity Sensor, LiPo Battery, Charger.
The impedance sensor is made by a PCB board and a copper wire sticket in a spiral form to make a good contact with the skin. This sensor is connected to PmodIA - impedance analyzer.
Step 3: Wireless Sensor Node - Connections
Connect all the elements as in the pictures. For a minimal design of the components, remove all Pmod connectors and use only wires instead of them.
Step 4: ChipKit Cmod - Software
We need to compile the source code and upload the program for sampling and transmitting data on CHIPKIT CMOD microcontroller, “heart” of the acquisition system. This program will take care of getting and sending skin impedance, temperature and humidity to the processing system (ZYBO development board), through the PmodRF2 module. To program the ChipKit Cmod we need MPIDE software.
Step 5: Setting Up the Base Station
First of all, connect the OLED display and the radio tranceiver to ZYBO as in the diagrams. Also place a memory card into the slot.
Further we need to configure the ZYBO development board. We will use two specialized programs to do this.
1. Vivado is used for hardware design and configuration (FPGA part).
2. Xilinx SDK is used for software development, to program and configure the ZYBO platform.
For this step, you have to use mainly the Xilinx SDK for hardware configuration and software uploading.
Step 6: Display and Saving the Information
All information (values ) is displayed using an OLED display. The impedance is plotted on the first screen. Also you can use the push buttons to navigate through the menu and view the actual values of impedance, temperature, humidity and sampling frequency. There is also a settings menu.
Step 7: Data Processing
This is the most beautifull part of the project. At this step we will test our creation and will see the variation of skin impedance when the subject is doing his daily activities.
As you can see in the picture, the skin impedance decreases with the effort, stress or panic. Also the skin temperature is increasing in such conditions.
Thank you! :)