ELECTRICAL DRIVE AND CONTROL OF AN ELECTRIC MOTOR STEP BY STEP BY STEP BIPOLAR

"PWM, (Pulse Width Modulation) is the most effective way to control analog circuits using numerical outputs by changing the duration and frequency of the signal. The duration of each state t1 and t2, so the filling factor, where T = t1 + t2 = constant. If only one of the times (t1 or t2) varies, then the Tt period of a cycle varies, so the f = 1 / T frequency varies. The PWM signal is actually a modulated rectangular signal over the duration by modifying the duration of each period t1, t2 of the cycle as well as the change in frequency. The maximum benefit of a stepper motor can only be obtained if it is ordered correctly, this requiring a direct current source, an electronic switch and a controlled pulse generator (numerical information). The frequency of the CLOCK cycle is measured in Hz and the filling factor is measured in percentage (%). The amplitude of the output signal is constant even if the amplitude of signals producing the fill factor varies. "

DETERMINATION OF SOIL TROPHICITY BY ELECTROPHYSICAL METHOD. MESSAGE 1. DEVICE AND LABORATORY TECHNIQUE

The purpose of this work was to develop a device and technique for determining the soil trophiсity using the electrophysical method based on the measurement of the soil specific resistivity (SR). In the proposed device the F. Wenner installation is used as a sensor. The device has a modular design and includes a voltage boosting module, a PWM generator of rectangular pulses, a rectangular signal inverter and an H-bridge that switches the polarity of the power supply in order to prevent polarization of the electrodes. The metrological characteristics of the specific resistivity measurement as well as the influence of the electrodes immersion depth in the substrate studied are determined. Its significant influence and nonlinear character which was well approximated by the power function were established. The simplest equations for bringing the measured values of the RS to a certain depth of the electrodes in the object studied are proposed.