## 2 Materials and Methods
### Test Objects
#### 2.1.2 Dedicated Electronic Controller for TEM Power Supply  
An essential part of the developed PCS is the controller, which is a dedicated embedded electronic system whose main role is to provide a controlled electric power supply to the TEMs. The electric energy is drawn from a powerbank with a 5 V output voltage. The controller is connected to an undergarment temperature sensor, and it executes a program for the temperature and power regulation [5]. This regulation is performed independently in each of its three output channels, with two TEMs connected to each channel.  
The block diagram of the electronic system is shown in Figure 4. Its main components are:  
* an auxiliary DC/DC switched-mode power converter (SMPC) with an integrated analog controller--to supply the control electronics with a 3.3 V voltage;
* a semiconductor power switch--for turning on and off the auxiliary SMPC;
* a power-button-pressing detector with a latched output state--for controlling the power switch;
* three digitally controlled output DC/DC SMPCs (one per output channel)--for supplying the TEMs in each channel;
* current sensors (one per channel) in the form of shunt resistors with dedicated voltage amplifiers--for measuring the channel output currents;
* a microcontroller;
* a three-button keyboard;
* a light-emitting diode (LED) bar display;
* a Micro Secure Digital (SD) card interface--for configuration and measurement data storage;
* a UWB radio module--for communicating with the rest of the smart work environment infrastructure using the NGIoT architecture.  
The output power converters employ the buck topology, with each one containing a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) switch, a Schottky diode, and an LC (inductance-capacitance) filter. The MOSFET switches are driven by pulse-width-modulated (PWM) signals generated by the microcontroller, with variable duty cycles \(D_{[1..3]}\) that are continuously updated according to the control program. The LC filters ensure constant output voltages with low ripple, which is crucial for an efficient TEM operation.  
Figure 3: High-visibility protective clothing intended for a use with active clothing: (**a**) T-shirt; (**b**) trousers.  
The microcontroller measures the output channel voltages \(U_{Q[1..3]}\) and currents \(I_{Q[1..3]}\) using a built-in analog-to-digital converter (ADC) to obtain feedback information on the output power in each channel. It also communicates with the undergarment temperature sensor via the Inter-Integrated Circuit (FC) interface as well as with the SD card and the UWB module via the Serial Peripheral Interface (SPI) bus. Two buttons of the keyboard are polled by the microcontroller to check if the user wants to increase or decrease the cooling intensity. The current setting of the TEM power levels is indicated on the LED bar display.  
The TEMs operate in an alternating mode, as described in more detail in [5]. The supply power per module is either regulated to obtain the requested temperature, with a maximum limit of 1.5 W, or to bring it down to a standby value of 0.5 W. The duration of each of these phases is 60 s.