The steam light on the soot blower requires an indicator lamp that blinks at two different frequencies. When a steam fault occurs, the steam light starts blinking rapidly (2 Hz). After acknowledging the steam fault, the light blinks slowly (1 Hz) if the failure persists. When the fault disappears, the light stops blinking and instead indicates the status of the steam sensor.

An application example below demonstrates this behavior:

• If in1 = '1', the light blinks slowly (500 ms on, 500 ms off, 1 Hz)
• If in2 = '1', the light blinks rapidly (250 ms on, 250 ms off, 2 Hz)
• If in3 = '1', the light remains constantly on
• If all inputs in1, in2, in3 are '0', the light remains constantly off

Note that if more than one input is activated simultaneously, in2 overrides in1, and in3 overrides both in1 and in2.

Function

The application's function is based on the bo data type, which consists of the members bv (Binary Value) and pw (Pulse Width). The bv member defines the current status of the binary bit, while pw controls or indicates the duration for which this status is maintained.

In the example, fast blinking is achieved by writing a binary '1' with a 250 ms duration to a BOU8 channel. This write operation occurs once per module execution, which takes place every 500 ms (Suoritus = Execution parameter at the top of the module is set to 500 ms). The status of the BOU8 channel returns to '0' after 250 ms, causing it to oscillate at a frequency of 2 Hz.