After the BLDC motor driver, had been introduced, its demand and use has increased past the mid- 20th century. Be it because of its flexibility that it can be converted into small size, or is it because it is much lighter than the conventional dc motor with brushes, the product is in the most preferred list of people.
The device demands information about the rotor- position to set the favorable commutation angle. And, for this purpose a Hall effect sensor is employed in the project. However, doing so can increase the overall project cost. And, therefore we often prefer a sensor-less option. A simple DRV10866 driver IC just serves our purpose right. It drives a BLDC rotor and eradicates the use of position sensors in the circuit. The fact which makes this project quite interesting is that the speed of fan used in this project can be altered smoothly unlike the speed changing mechanism in normal AC fan.
Circuit and Working of BLDC Motor Driver Circuit
The entire layout of the above proposed project; BLDC Motor Driver Circuit is given in fig.1. As illustrated in the figure, the chief component is a NE555(IC1) and other components like a DRV10866 (IC2) accompany the chief component to reach the goal of the project.
IC2 that controls the fan does the work of driving a small three-phase BLDC motor (M1). Probably you get it now, the circuit depicts a clear picture of sensor-less three-phase motor driver. The circuit also includes power MOSFETs that have current driving capacity up to 680mA peak value. Keeping the concept of project in mind, IC2 is selected since it is manufactured for low noise and low component-count fan-motor drive applications.
To keep control of three-phase motor, a 150° sensor-less back emf scheme is used.
Talking about the BLDC Motor Driver Circuit set up details, as stated earlier IC2 is the central- component. Pin 1 of IC2 is fixed with a 100k pull-up resistor (R2). Similarly, pins 2,4,6 and 7 of IC2 are connected to common, phase A, phase C and phase B of the BLDC motor, respectively. Two ICs; IC1 and IC2 are bonded by the path established by connecting pin 10 of IC2 with pin 7 of IC1. This bond ensures the production of pulse-width modulated (PWM) signal from IC1 which helps to control the speed of the BLDC motor incorporated in the circuit.
Thus, PWM signal reaches the pin 7(DIS) of IC1 and is available at that pin only not at the assigned output pin 3 of that particular IC. The duty cycle of the PWM signal is recorded to be approximately 25kHz. It can be varied in between 5% to 95% with the use of potentiometer VR1. Changing the duty cycle of PWM signal also affects the speed of the BLDC motor. A clockwise variation in potentiometer lowers the duty cycle and slows down the fan speed and anti-clockwise variation increases both duty cycle and fan speed.
Construction of BLDC Motor Driver Circuit
Figure 2 shows actual-size, single-side PCB design for the BLDC motor driver circuit. Figure 3 depicts component layout for the same. As shown in the BLDC motor driver circuit place all the components in the assigned order and avoid any possible errors which may degrade the implementation process. As shown in figure, IC2 must be fixed on solder side of the PCB.
Figure 2: Solder Side PCB Design for BLDC Motor Driver Circuit
Figure 3: Component Side PCB for BLDC Motor Driver Circuit
Once the assembling process is completed, check for possible errors and then provide the circuit with a 5V power at CON1 connector.
PARTS LIST OF BLDC MOTOR DRIVER CIRCUIT
|Resistor (all ¼-watt, ± 5% Carbon)|
|R1 = 10 KΩ
R2 = 100 KΩ
R3 = 3.8 KΩ
VR1 = 5 KΩ
|C1, C3 = 10nF
C2 = 0.1 µF
C4 = 2.2 µF
|IC1 = NE555
IC2 = DRV10866
ZD1, ZD2 = BAT41
|M1 = Brush Less DC Motor (BLDC motor)|