The goal of this bachelor thesis is to build a simple lie detector with the help of Arduino technology. The lie detector was achieved on an Arduino UNO microcontroller platform and a combination of a module for measuring heartbeat, two light-emitting diodes to visually show the results and a 10 kΩ resistor to help regulate electric current. The lie detector determines if the person is telling the truth or if he is lying, based on two physiological reactions: electrodermal activity and pulse. The pulse is measured with the help of the photo module for measuring heartbeat, while the electrodermal activity is measured with the help of two free electrodes, connected to the Arduino microcontroller via the (10 kΩ) resistor. A program code in the Arduino integrated development environment allows a visual display of the measured physiological reactions in the Arduino serial plotter. The interrogator first measures the pulse and the electrodermal activity of the subject that is being tested, then he determines the upper limit for which he thinks the subject is lying and finally he conducts the interrogation. To determine a lie, the subject's electrodermal activity or pulse needs to accelerate over the previously determined limits. If none of the subjects physiological reactions crosses the defined limit, a green diode will light up. However, if at least one of the physiological reactions crosses the limit, a red diode will light up. The lie detector has been tested and its functionality has been established and its accuracy has been determined with experimental testing.