Echelon LonPoint Application and Plug-In - Manual (Page 33)

The LonPoint Application and Plug-in Guide 3-7
output goes On and the count as reported by the Analog network variable is set
to 0. Cans continue: 1, 2…, then, some downstream device controlling the boxing
process sees the Digital network variable to be on, boxes the cans, and sends
CLEAR
to the Control network variable. The digital output goes Off. Cans
continue three, zero and the process repeats.
There are no race conditions, however there is a performance requirement – the
Control network variable must be cleared before the terminal count is reached a
second time in order to get a new signal. If the Control network variable is not
cleared before the terminal count is reached, counting will continue between zero
and the terminal count, the Digital network variable will remain on, and the
overrange bit of the object status for the Digital Input/Counter function block will
be set. This status bit can be used as an indicator that the control loop is not
being closed. If the Control network variable is not connected, the overrange
status bit will not be set.
It is good design practice for the output network variable that updates the
Control input network variable to have a send heartbeat so that the loop works
even if some messages are lost.
Control TC
Analog
Can Counter
LoadBox FB
Boxing Machine
D1 Index
DE- 1
On-Time
Measures the accumulated on-time of the hardware input. A typical application
for this mode is monitoring equipment usage time in order to determine when
maintenance is due. Each half-second, an internal counter is incremented if the
input is on. The count value is processed and sent to the Analog network
variable (an appropriate network variable type for the Analog output network
variable in this mode is SNVT_time_f; the units are seconds). The Control
network variable governs processing. The input is sampled and the Digital
network variable is updated at 500ms intervals.
The maximum on time that can be measured in this mode is 20 years.
The on-time value is kept in RAM. The value is copied to non-volatile EEPROM
once per day just past midnight as determined by the node object, whenever the
node is sent offline, and whenever the functional block is commanded to go to the
disabled state. Power cycles or watchdog timeouts will lose the RAM on-time
values. After recovery from any of these events the last count stored in EEPROM
will be loaded into the RAM counter
If the hardware input has been configured for Dry Contact the input may be
configured to be debounced with a configurable time period. If the hardware
input has been configured for voltage input (5V, 12V, 24V, or 31V) debounce is
not supported