circuit explanation of stepper motor

  
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Darlington connection-type transistor is used for the drive of the coil. As for the Darlington connection, 2 stages of transistors are connected inside in series. The `hfe` of this transistor is the multiplication of the `hfe` of each transistor inside. In case of 2SD1209K which was used this time, the hfe is over 4000. Because the ratio of the in
circuit explanation of stepper motor - schematic

put electric current and the output current is big, the rising edge and the falling edge of the control signal can be made sharp. The diode to be putting between the collector and the power is for the protection of the transistor. When the transistor becomes OFF from ON, the coil of the motor tries to continue to pass an electric current and generates high voltage. An electric current by this voltage is applied to the diode and the high voltage which applies over the transistor is prevented. TR1 becomes ON condition when RB7 becomes H level. In this condition, the electric charge of capacitor C1 flows through the transistor and the voltage of the both edges of the capacitor becomes 0 V almost. When RB7 becomes an L level, the transistor becomes OFF condition. In this condition, the electric current flows through VR1 and R4 into capacitor C1 and the charging to the capacitor begins. The voltage of the both edges of the capacitor becomes high gradually as charging is done. As for the change of this voltage, refer to "Integration circuit". The voltage of the capacitor is detected by RB5. The software of PIC interrupts the control of the motor until it checks RB5 after making RB7 an L level and RB5 becomes H level. When making the value of VR1 small, the charging time of the capacitor is short and the control of the motor becomes quick. The control of the motor becomes slow when making VR1 big. The speed control range can be...



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