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Parts explanation of Stepper Motor controller

Stepper motor ( 42SPM-24DCZA )

This is a 2-phase unipolar PM type stepper motor with 48-poles.
Step angle:7.5 degrees ( 360 degrees/48 )
Drive voltage:5 to 6V
Coil current:250mA(5V)/2 coils


The control of the stepper motor is done by this PIC. To have explained in the operation principle, coil, coil, coil and coil are controlled by the software.

3 terminal regulator ( 78L05 )

This is used to make the stable voltage of +5V.
A 100-mA type is used.

Motor drive transistor ( 2SD1209K )

This is a Darlington connection-type transistor.

At first, I used 2SD1590 ( 8A type ) as the transistor for the drive. However, in case of the motor which was used this time, the coil current was about 250 mA. So, I changed into the small type transistor. The maximum collector current of 2SD1209K is 1A and "hfe" is more than 4000.

Transistor for the motor speed control ( 2SC1815 )

This is the transistor to control the speed of the motor.

Diode for the transistor protection

This is the diode to protect a transistor from the back electromotive force which occurs with the coil of the stepper motor. It depends on the kind of the stepper motor but it is to be OK if it is possible to pass a hundreds-of-mA electric current.

Baton switch

This is a switch for the clockwise rotating, the counterclockwise rotating or making a motor stop.

IC socket

This is the socket to mount PIC16F84A.


This is a 4 MHz resonator.

Variable resistor for the speed control

B type is used.


It is to be OK at 1/8 W.

Resistor for pull up

This is the series resistor to be using for start/stop switch pull up.

Multilayer ceramic capacitor

This capacitor is used to bypass the high frequency noise of the input and output of the power supply.

Electrolytic capacitor

This capacitor is used as the ripple filter capacitor of the power circuit.

Printed board

This is an universal printed board with 15 x 25 halls.

Wiring terminal

This terminal is used to connect a power supply wire and the variable resistor for the speed control.

Connector for the stepper motor connection

A 6-pin connector is used to connect a stepper motor.
The motor used this time, 5-pin connector is OK. Because the power of the X coil and the Y coil is connected inside the motor. However, a power line is divided by the kind of the motor. So, 6-pin are used for two power lines to be able to be connected.


This is used as the leg of the printed board.