fact, a high frequency PWM wave produces, in a coil, a voltage whose amplitude value is the mean va-

lue of the square wave.

The motor data sheet displayed in fig. 2, clearly shows that "U-W" phase must be supplied positive

when sensor "H1" is high, "W-V" when sensor "H2" is high and so on. This is true because the triangular

connection was preferred in the coils arrangement. AND output is, then, a Pulse train whose duration is

the same of the Hall signal. This pulses train is used to drive each leg of the bridge L298.

L298 is a monolithic dual full-bridge driver designed to accept standard TTL logic levels and drive induc-

tive loads such as relays, solenoids, DC and stepping motors. Enable input signals are available to allow

a software protection. Internal circuitry provides the appropriate dead-time in order to avoid a "cross-con-

duction" along the leg.

ST52x301 provides, by means of an internal peripheral, a PWM wave that can be varied by software.

ST52x301 PWM frequency is chosen as compromise between acoustic noise in the motor and losses in

the power stages of the bridge. A 19 KHz wave frequency was used in the implemented application.

SOFTWARE DESCRIPTION

Before to discuss about ST52x301 software configuration, it is important to note some HW connections

in the schematic. Bit "0" (pin 9) of the parallel port is used to enable the power stage only after power-on

reset, then parallel port must be configured in OUT mode. The analog input AIN0 (pin 43) is used to read

the voltage reference. A voltage between 0 + 2.5 V present on this pin, is converted in the range 0 +

255.

External INTerrupt pin (27) is used to read one Hall sensor signal period in order to calculate the instan-

taneous speed. This digital input will be configured both in negative or positive edge trigger to produce

an internal software interrupt.

Fig. 8 displays how to configure A/D peripheral with 3 inputs, TRIAC peripheral in PWM mode at 19 KHz,

the used global variables.

The following figure reports the main program in term of graphical programming. The appendix at the

Figure 8 . Peripheral configuration

®

Brushless Motor Fuzzy Control by using ST52x301

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