PIC controller controls the electric motor

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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The PIC controller controls the motor. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electric motors

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This compilation is about two designs on a PIC controller, described on the website of the Japanese radio amateur Seiichi Inoue. The first of them is designed to control the speed of the DC motor, the second - the stepper motor.

Schematic diagram of the DC motor shaft speed controller is shown in fig. 1 (a detailed description in English can be found at ).

PIC controller controls the electric motor

The device is made on the microcontroller (MK) PIC16F873. Its clock frequency (10 MHz) is set by a ZQ1 quartz resonator. Power is supplied to the main electric motor M1 through a powerful field-effect transistor VT2, the gate of which receives rectangular pulses from the output of the microcontroller CCP1 through a matching stage on the transistor VT1. The pulse frequency is constant, and the duty cycle can be changed, thus adjusting the speed of the motor rotor.

The shaft of the electric motor M1 is mechanically (through a 1:1 gear two-stage transmission) connected to the second electric motor, which is used as a generator. The voltage generated by it through the diode bridge VD1 and the voltage divider R1 - R3 is fed to the input AN0 of the analog-to-digital converter, which is part of the MK. Zener diode VD2 with a stabilization voltage of 5 V protects this input from damage, capacitor C5 smoothes out the ripple of the rectified voltage.

The required speed is set by a variable resistor R2 with a functional characteristic A.

An increase in the voltage supplied to the AN0 input indicates that the motor shaft speed is increasing. In response to this, the MK reduces the duration of the pulses at the output of the SSR1, and the rotational speed returns to the previous value. When the voltage generated by the motor-generator decreases, the duration of the pulses increases and the rotational speed increases.

The line of LEDs HL1 - HL8 allows you to visually control the speed of the motor shaft: the number of luminous LEDs increases with its increase.

The device is powered by a stabilized voltage of 5 V, taken from the output of the integral stabilizer DA1. The motor M1 receives an unstabilized voltage from a separate source.

The controller is assembled on a 70x45 mm breadboard.

Stepper motor control devices usually contain shift registers that form the necessary sequence of pulses supplied to the windings. The proposed device on the PIC controller also allows you to change the direction and adjust the speed of the rotor. Description of the design, drawing of the circuit board and commented source codes of the microcontroller program are located at .

The schematic diagram of the device is shown in fig. 2.

PIC controller controls the electric motor

The main one is MK PIC16F84A. The clock frequency (4 MHz) sets the quartz resonator ZQ1. On the elements R8-R10, C6 and the transistor VT5, a generator is assembled, the frequency of which can be smoothly changed by a variable resistor R9 with a functional characteristic A. The voltage from the capacitor C6 is fed to the input of RB5 MK DD1. After it exceeds the threshold, a high level voltage appears at the output of RB7. The opened transistor VT5 discharges the capacitor, after which the cycle repeats.

When moving the engine of the resistor R9 from one extreme position to another, the engine speed M1 changes from 27 to 128 min-1. It should be noted that with increasing speed, the torque on the motor shaft decreases. The device has no feedback, so the rotational speed depends both on the resistance of the input part of the resistor R9, and on the load on the shaft.

The outputs RA0 - RA3 MK through the keys, made on composite transistors VT1 - VT4, switch the voltage on the windings of the stepper motor. Diodes VD1 - VD4 protect transistors from breakdown by voltage pulses that occur at the moment they are closed.

Buttons SB0 - SB2 are connected to the first three bits of the RB port (RB1 - RB3) of the MK, with the help of which they change the direction of rotation of the motor shaft and stop it.

All parts (with the exception of the motor and variable resistor) are mounted on a 70x45mm breadboard. The appearance of the device is shown in fig. 3.

PIC controller controls the electric motor

Stabilizers 78L05 and 7805 are replaceable by domestic KR142EN5A (B), transistor 2SC1815 - by any of the KT3102 series, zener diode RD-5A - by domestic KC147A. Transistors VT1-VT4 (see Fig. 2) must withstand the current of the motor windings and have a base current transfer coefficient of about 4000. The VD1 rectifier bridge (see Fig. 1) is KTS407A or assembled from low-power silicon diodes. LEDs HL1 - HL8 - any of the AL307 series.

Source texts of programs

See other articles Section Electric motors.

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