Delta Electronics Ethernet Extension Module DOP Dokumentacja Pobierz pdf (Strona 140)

Chapt er 5 Ex am ples of Pr o gramming

5-1 3

5.4 PWM─Sprayer Valve Control Program

25%

50%

100%

X2 X3 X4

START

STOP

1. Control purpose

 In order to reduce the energy lost during the gradual shut-down/start-up process, we apply

the switching method which immediately turns on and turns off the current valve. The

switching method is somewhat like cutting off a current, and is therefore called a clipper.

However, in the practical application we put a transistor between the power and the motor to

perfom the function of a clipper. A pulse signal will be applied to the base of the transistor so

as to generate a pulse current between the base and the emitter. The input voltage of motor

is in proportion to the t

off

value. Therefore, the motor voltage could be adjusted by

modulating the t

off

value. There are various methods for modulating this value, and the

most common one is to adjust the time (t

) for which the valve is ON rather than adjusting

the number of times the valve is ON during a a particular length of time. The method is

called PWM (Pulse-width modulation).

 Users can control the the degree to which the sprayer vale is opened by adjusting the t

off

value of PWM (24 V). The opening degrees which can be selected are 25%, 50%, and

100%.

2. Devices

Device Function

X0 X0 is ON when the START button is pressed.

X1 X1 is ON when the STOP button is pressed.

X2 X2 is ON when the 25% button is pressed.

X3 X3 is ON when the 50% button is pressed.

X4 X4 is ON when the 100% button is pressed.

Y0 Controlling the degree to which the the valve is opened

The degree to which the the valve is opened

is stored in

D0.

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Delta Electronics Ethernet Extension Module DOP Dokumentacja Strona 140