Configuring DL05 Event Logging and Serial Printer Output

The Photohelics already switch signal lamps when a pressure zone leaves specification, but a lamp and counter alone cannot record when an excursion started, how long it lasted, or provide a run-related printout. Treat this as an event-logging job: detect each transition, preserve a timestamped record, and send that record to a serial output path.

Define what counts as one pressure excursion

Before adding hardware, agree on the event boundary. A practical definition is one excursion per transition from in-spec to out-of-spec; the return to in-spec closes that event and supplies its duration. If the customer instead wants separate counts for each pressure switch transition, document that explicitly. Counting both edges as separate excursions doubles the apparent event count.

The Photohelic signals provide the state transitions for the lamps and the event logic. The PLC must distinguish the transition into an excursion from the continuing out-of-spec state; otherwise, a scan-based counter may increment repeatedly while the contact remains active. Confirm whether each Photohelic output is a maintained state or a momentary signal, and confirm the PLC input wiring and electrical compatibility before programming.

Check: With a controlled test input or approved process test, confirm that the lamp changes state as expected and that one out-of-spec entry produces exactly one event start.

Choose the logger before buying a counter

A standalone counter can show a total and provide a reset, but it does not by itself meet the added requirement for event time, duration, and process-run printout. The DL05 is a possible PLC-based approach, but the record requirements—not the counter display—should determine the architecture.

Do not select a PLC on the assumption that it automatically supplies a valid wall-clock timestamp or retains an unlimited event history. Check the unit’s documentation and installed configuration for a usable time source, retention behavior, and available memory. If those checks fail the requirement, change the architecture before commissioning.

Check: Approve a written record layout that names each required field—zone, event start, event end or duration, and process-run identifier—then verify that the chosen hardware and interface can supply each field.

Build the event state and duration logic

Implement event capture as a state change, not as a continuously true condition. For each pressure zone, detect the in-spec-to-out-of-spec transition, capture the start time once, and mark the event active. On the return transition, capture the end time or calculate elapsed time from the start, then close the event. The event count should increment at the agreed point, normally at entry if the count means excursion starts.

1. Read the Photohelic input and establish its normal/in-spec state.
2. On the transition into out-of-spec, create one event record and capture the start time.
3. While the input remains out-of-spec, keep the event active without incrementing the count again.
4. On return to in-spec, capture the end time or duration, close the record, and make it available for the selected display or print path.

Define what the logic does after a power interruption or a state transition while the PLC is restarting. Also decide how to handle an event that is still active at shift or process-run end: print an open event status, or wait until the return transition. These are application decisions; do not silently treat an unfinished event as having a known duration.

Check: Simulate one complete excursion and a prolonged out-of-spec input. Confirm a single count, one start time, and one closure only when the pressure returns in spec.

Set up Port 2 for the serial device

The described DL05 print arrangement uses a serial printer on Port 2; a dumb terminal or a PC running HyperTerminal was also identified as a receiving option. A parallel printer is not the described connection. Configure the secondary communication port protocol as Non-Sequence, then set the baud rate, data bits, parity, and other serial parameters to match the receiving device.

1. Check the printer or terminal manual for its serial interface settings and connector requirements.
2. Set the PLC secondary communication port to Non-Sequence and match the documented serial parameters at both ends.
3. Connect a serial receiver and test basic communication before integrating event logic.
4. Consider XON/XOFF only when the receiver supports it; it was suggested for printers with a small buffer, not as a universal requirement.

Do not troubleshoot print formatting until the port mode and serial settings match. A receiver configured for different baud, data bits, or parity can produce unreadable characters or no usable output even when the program issues a print instruction.

Check: Send a short test string and confirm that the receiver displays or prints the same characters cleanly. If it does not, recheck port protocol and matching serial settings before proceeding.

Format a readable event record

The cited DL05 method uses the PRINT instruction. The example below illustrates literal text, a register value, a BCD-formatted value, and $N as carriage return/line feed; it is a syntax example, not a complete event logger.

PRINT K2 "This is V2000 " V2000 "$NThis is V2001 in BCD " V2000:B "$N "

The example output contains the text and values on separate lines. Build the actual record around the fields the operator needs to reconcile an excursion with a process run. Include clear labels and a record boundary so a printed page remains interpretable after the run. Verify the exact operand and formatting rules in the DirectSOFT PRINT help or the applicable 05 user manual before entering production code.

Printing is not the same as retaining history. Decide whether the printer is the official record, whether the PLC must retain records until they print, and what should happen if the printer is disconnected or stops accepting data. Do not clear a pending record merely because a print command was attempted; verify the chosen design’s acknowledgment or operator recovery method.

Check: Print a test record containing representative values and compare every label, line break, numeric format, and record boundary with the approved layout.

Control reset access and daily totals

If the operator needs only a daily total, provide a clear daily reset method and define who may use it. A display pushbutton was proposed where unauthorized reset protection was not needed; a pushbutton enclosure with a keyswitch was proposed where reset access should be restricted. A reset is an operational control, not a substitute for event records.

Separate the daily counter reset from event closure and from any stored or printed history. Resetting a display total must not erase an active excursion’s start time or discard an unprinted event unless that is an explicitly approved behavior. If the customer needs auditability, define how the reset is recorded and how the total is associated with the process run.

Check: Test the normal reset method and, where fitted, the restricted reset method. Confirm the daily total changes as intended while active and completed event records remain available according to the approved design.

Commission the complete event-to-print path

Commission with a controlled test for each pressure zone and with the actual receiving device. A successful lamp test proves only the discrete signal path; it does not prove timing, record retention, process-run association, or serial output.

1. Verify each zone’s normal state, out-of-spec transition, and lamp indication.
2. Generate a complete excursion and compare the count, start time, end time or duration, and zone identity with the test sequence.
3. Run a second excursion while the first event input remains active long enough to prove the counter does not repeat-count.
4. Exercise the daily reset and confirm it does not corrupt the event record.
5. Print the record and reconcile its values and run association against the display and test observations.
6. Disconnect or inhibit the receiver in a controlled test and verify the documented recovery path for pending output.

If time or duration is wrong, first compare the event transitions and time source against the test sequence. If records are correct in the PLC but print output is wrong, isolate Port 2 settings and formatting separately. Change one layer at a time and repeat the same test sequence.

Check: Release the system only after the test log, displayed values, and printed records agree for entry, return-to-spec, reset, and receiver recovery.

FAQ