Design and testing of electronic circuits to improve performance of automatic adjustment systems which equip sprinkling machinery

Abstract

The use of electronic regulators, in order to correlate the working parameters at sprinkling machines, requires a study to assess the performances of the regulation process in working conditions. Given that the parameters to be correlated are physical sizes, the equipment must be fitted with appropriate sensors to perform the conversion into electrical sizes. Processing the input information, present in the form of electrical voltages, can be achieved only by a specialized circuit of comparator type. To operate properly the liquid flow control valve, this circuit will have to generate different commands in the form of electrical signals. Having low values, these signals are not at the required level to operate the electric motor used for actuating the control valve. Therefore, it is necessary to amplify them to an appropriate level by a power amplifier. The amplifier must be able to put the motor rotor in short-circuit mode with the cancellation of each adjustment command. This mode of operation ensures strong braking and stoppage almost instantaneously of the rotor. This fact has favourable consequences on accuracy of flow adjustment. For optimum operation of the equipment, the design of these circuits was done so as to ensure a maximum sensitivity by eliminating self-oscillating work regimes. Experiments were performed simulating on adequate stands the real working process of a sprayer, equipped with such a regulator. Testing in laboratory conditions has the following purposes: checking the functioning of some important electronic circuits, which are components of the adjusting system; establishing the performances of the adjustment system, from the point of the quality of the adjusting process. Analysis of the obtained results from the tests demonstrates that the hysteresis of the comparator circuit is10 mV, in accordance with the setting, ensuring a good sensitivity during operation and also the elimination of the over-adjustment phenomenon. Amplifying the signals at the 9 V value, the power amplifier ensures a proper reversal of the sense of rotation of the actuating electric motor and putting in short-circuit mode for its quick stop. Due to the correct operation of the designed circuits, the adjustment function is performed correctly, the deviation from the prescribed adjustment report being just 0.2 %.