Pressure control system block diagram as shown:
The system can be adjusted by the amount of water storage tanks. Reservoir pressure within the pipe to pass through the sensor, the sensor to output a voltage proportional to the pressure to be monitored signal (Uo), sent to the comparator. Select the user by changing the pressure on the output of the reference voltage circuit (UREF) to set the pressure. Compared with the UREF will Uo, then through the motor drive circuit to control the motor / pump on or off. When the reservoir pressure below the set pressure to open the motor / pump, a water injection to increase reservoir pressure. Once the pressure reaches the set value, immediately turn off the motor / pump.
A practical circuit pressure control system as shown. 12V power supply through the 78L05 (IC2) to obtain 5V voltage, a separate power supply to the MPX5100. The remaining circuits are used 12V power supply. MC33033 (IC1) for the motor controller, MC34272 (IC3) for dual op amp (now only one of the op amp.) To improve efficiency, the motor drive circuit using a MPM3002-type drive module, the internal P-channel power by the two FET (V1, V2) and two N-channel power FET (V3, V4) composed of H bridge, drive current up to 4A. Can drive DC brush motors. To avoid noise or due to system pressure fluctuations caused by small measurement errors, but also specifically to increase the delay circuit, using MC33033 internal error amplifier and external resistors R8 ~ R10, form a hysteresis comparator. Its working principle is open when the motor when the UoUREF; With rising pressure tank, when the sensor output voltage is equal to the reference voltage and the hysteresis voltage (UH) of and, that is, when Uo = UREF UH off the motor, the system reduces the pressure . Since then, the sensor output voltage will always be equal to the motor is turned down to the reference voltage. Take R8 = R9 = 10kO, R10 = 300kO, the hysteresis voltage is 0.3V, corresponding to the lag pressure 7.5kPa. Circuit switch S can be used to control the motor forward or reverse.