Siemens LOGO! V8 Fertigation Programming: 4x Daily 10-Min Cycles

Siemens LOGO! V8 Fertigation Programming: 4x Daily 10-Min Cycles

Fertigation is the combined injection of fertilizer into an irrigation line. The canonical control requirement is "run the pump four times per day, each cycle for ten minutes", synchronized to local civil time. The Siemens LOGO! V8 (the 8th-generation 6ED1052 family, marketed as LOGO! 8.3 / FS4) is sized exactly for this class of machine: a built-in real-time clock with daylight-saving compensation, weekly and yearly timers, an astronomic option on the timer blocks, and (on FS4) NTP client support over Ethernet. This reference builds the program from primitives, validates it in simulation, and addresses the most common failure modes seen when commissioning a first-time LOGO! project.

1. Hardware Identification Before You Program

Confirm the exact order number (MLFB) printed on the front of the base module, because behavior differs across revisions:

Verify the feature set under LOGO!Soft Comfort > Tools > Select Device or by reading the device's Diagnostics > FW Version web page once it is on the network. NTP and astronomic timers are gated behind FS4+; if your base module is FS02/FS03, plan to use the weekly timer block driven by the local RTC and an external NTP-to-Modbus gateway, or accept manual time drift correction.

2. Fertigation System I/O Plan

Map the physical actuators to LOGO! digital outputs. A minimal fertigation skid has three outputs: main irrigation pump, fertilizer doser pump, and a master enable indicator. Reserve one input for a low-pressure safety interlock so a dry-run shuts the pump off without the LOGO! continuing to count cycle time.

The relay-version base module (R suffix in the order number, e.g. 6ED1052-1HB08-0BA0) is recommended for inductive contactor coils. The transistor (T) variant is for 24 V signals only.

3. LOGO!Soft Comfort Workspace Setup

1. Open LOGO!Soft Comfort V8.x (matching the FW of your base module — V8.3 for FS4, V8.4 for FS5). Mismatched versions reject the LSC file with a dialog box; this is the most common reason a starter cannot open a downloaded program.
2. Select File > New. In the Properties dialog set the device to the exact MLFB printed on the front of your LOGO!.
3. Open Tools > Options > Simulation and confirm the simulator clock is unlocked. This is what lets you step time by one minute in five-second simulation ticks.
4. Set the PC clock and timezone in Tools > Options > General. The simulation runs against the PC clock, not against a manual offset.

4. Time Base Selection: Why "Hours as Seconds" Hurts You

It is a common shortcut during simulation to set a "10-hour" timer and run the simulation for 10 seconds. The shortcut is fine for the on-delay block, but it is the wrong tool for a daily-schedule problem: a 10-hour on-delay is a one-shot, not a repeating daily trigger. The correct primitive is the Weekly Timer (block B13 in the LOGO! function-block list, Special Functions > Timers > Weekly Timer), which compares the LOGO! internal RTC against up to three on/off cam pairs per week.

5. Building the 4x Daily 10-Minute Schedule with Weekly Timers

Configure four independent Weekly Timer blocks, one per irrigation window. Each block has three on/off cams; you only need one cam per block. For a typical 06:00, 12:00, 18:00, 00:00 schedule:

The pulse output of each weekly timer becomes the trigger input of a shared 10-minute on-delay (B04). The on-delay's output drives the pump contactor Q1 via an AND with the low-pressure interlock I1 and the manual-stop I3. The off-delay (B05) is left at zero — its job is to keep the cycle on a hard 10-minute cap even if a subsequent 12:00 cam arrives early because of a network time correction.

5.1 Ladder-Logic Equivalent in FBD View

[ B13a ] -- ( B04 = 10:00 min ) -- ( AND I1 /\ ~I3 ) -- ( Q1 )
[ B13b ] ----/
[ B13c ] ----/
[ B13d ] ----/

[ Q1 ] -- ( AND ) -- ( B06 off-delay = 30 s ) -- ( Q2 doser )

5.2 Why OR the Four Timers

The four weekly timers are evaluated in parallel; their outputs are wire-OR'd into the trigger of the on-delay. Any one of the four rising edges starts the 10-minute run. If two cycles were configured at the same minute, the second rising edge is ignored because the on-delay is already timing out — this is the desired behavior and prevents overlapping irrigation windows.

6. Real-Time Clock and Timezone Configuration

The LOGO! internal RTC is set from one of three sources, in priority order:

1. NTP (FS4+ only): Configured in LOGO! > Settings > Time/Date > NTP on the LOGO! web interface. Point to up to two NTP servers (e.g. 0.pool.ntp.org, 1.pool.ntp.org). Polling interval defaults to 60 s.
2. LOGO!Soft Comfort online clock: When connected via Ethernet/USB, the LSC toolbar Online > Set Time button writes the PC clock to the LOGO!.
3. LOGO!Soft Comfort SD card auto-load: A project on a Siemens SITOP / SD card with the time offset written will set the RTC at boot.

Daylight saving time is handled automatically on FS4 and later via the Time/Date > DST checkbox. On FS02/FS03 the clock does not auto-advance, and a one-hour slip will occur twice per year. Compensate by adding a Yearly Timer (block B14) on the spring/fall DST boundaries that drives a hidden B04 with a 60-minute on-delay to nudge downstream calculations, or accept the slip and re-sync quarterly.

7. NTP Time Sync on FS4 (Step-by-Step)

1. Connect the LOGO! Ethernet port to a routable network. Default IP is 192.168.0.10 on the first power-up; change it via LSC Tools > Ethernet Connections or via the on-board web UI.
2. Open a browser to http://<LOGO_IP>. Default credentials: user LOGO, password LOGO (change on first login).
3. Navigate to System > Time / Date. Enable NTP. Enter two NTP servers. Set timezone to your UTC offset.
4. Click Apply. The LOGO! will synchronize within one poll cycle. Verify by reloading the page — the displayed time should match an internet reference clock to within ±1 s.
5. Block diagram: the time-source flag is exposed to the program as a digital marker (M30 in the default symbol table) that can be used to blink a heartbeat LED when the clock is healthy.

8. Simulation Workflow

The Tools > Simulation (F3) toolbar in LOGO!Soft Comfort advances time against the PC clock by 1:1, so a 10-minute on-delay will take 10 minutes of wall time in simulation. To compress, do one of the following:

• Temporarily change the B04 setpoint to 00:00:10 (10 seconds) for test only. The simulation is intended for logic verification, not for proving real-time behavior. After verification, restore the B04 setpoint to 10:00 min before downloading.
• Use Simulation > Set Time of Day to set the PC clock near the next cam time, then step the simulator in 1-minute increments. The weekly timer will fire exactly on the cam minute.
• Use the Trigger Cam button on the simulation panel of the weekly timer to force a rising edge for logic-only testing.

Run the simulation for at least one full civil day (00:00:00 → 23:59:59) to confirm that all four cams fire and that overlapping cams do not start a second on-delay. The Diagram > Watch Window should show Q1 high for 10 minutes, four times.

9. Download Issues Specific to Starter LSC Files

The most common LSC download failure is a credentials prompt. Siemens Industry Online Support requires a registered Siemens account before any ZIP file will stream. The workarounds, in order of preference:

1. Create a free Siemens Industry Online Support account at the support portal. The same credentials are used to download the LSC installation package and every Knowledge Base article sample.
2. If you must access a project from a public forum, ask the original author to export via File > Export > LOGO! Project Archive, which produces a single .lma file. This file does not require an account to email and can be opened in any matching LSC version.
3. When the project opens with "file corrupted" or "unsupported block", the version mismatch is the cause. Update LSC from the support portal — it is freely downloadable after registration.

10. Verification & Commissioning Checklist

11. Troubleshooting Matrix

12. Extending the System

Once the four-cycle base system is stable, the same primitives scale to:

• Seasonal schedule — replace the four weekly timers with a single Yearly Timer (B14) and gate the 10-minute run by month. This is the typical summer/winter fertigation pattern.
• Dosing profile — add an analog input (LOGO! AM2 module) reading a flow meter on the main line, and multiply the 10-minute run by a scale factor to keep the fertilizer concentration constant as the irrigation flow changes.
• Remote start — on FS4, expose a webserver page on the LOGO! that lets an operator trigger an extra cycle on demand. The page is enabled under System > Webserver > User-defined page; binding Q1 to a VM (variable memory) address makes it visible to the page.
• Alarm SMS — a low-pressure fault can be written to a digital marker, polled by a Siemens LOGO! CMR (cellular router) and forwarded as an SMS or email alert.

13. Program-Block Map (Reference)