LOGO! 0BA6 Astronomical Clock: Troubleshooting Download Errors

Problem Summary

The Siemens LOGO! 0BA6 generation does not contain a native Astronomical Clock (Astro-Uhr / ASTO) function block in its firmware image. When a program built in LOGO! Soft Comfort references this block, the compiler accepts the program (because LOGO! Soft Comfort 7.x and 8.x ship with the block library active), but the transfer step fails on hardware 0BA6 with errors such as "Unknown function block," "Program incompatible with device," or "Block not supported by target hardware."

Two paths resolve the issue: (a) reconstruct sunrise/sunset logic with available 0BA6 blocks using a polynomial regression or seasonal table, or (b) migrate the project to LOGO! 0BA7 or 0BA8 where the native Astronomical Clock block is implemented in firmware. This article documents both paths and the verification procedure.

Affected Hardware and Firmware Matrix

The native Astronomical Clock block appears in the palette as B020 - Astronomical Clock from LOGO! Soft Comfort 8.0 onward. It is hidden when the active hardware target is set to 0BA4, 0BA5, or 0BA6.

Root Cause Analysis

Three independent faults generate the "Cannot download Astro-clock in 0BA6" symptom reported in the field:

1. Hardware-target mismatch. The project was authored against a 0BA7/0BA8 device and is being downloaded to a 0BA6 base module or expansion. LOGO! Soft Comfort only validates the hardware target during the PC → LOGO! transfer, not during FBD editing.
2. Firmware image older than 0BA7 on the device. The label on the unit may show 0BA6 even if the catalog number ends in -0BA7; conversely, early 0BA6 stock shipped pre-0BA7 firmware. Read the firmware string with LOGO! → Diagnostics → Device Information in Soft Comfort, or via the LOGO! display menu ESC → Diagnostics → SW Version.
3. Corrupted program memory or incompatible module cluster. Mixed clusters (e.g., DM8 on a 0BA6 base + DM16 on a 0BA8 expansion) reject transfers that contain blocks unique to one generation.

Step 1 - Select the Correct Hardware Target

1. Open the project in LOGO! Soft Comfort.
2. Press Ctrl+H or choose Tools → Select Hardware.
3. In the dialog, pick the exact catalog number printed on the front of the LOGO! base module (for example 6ED1052-1MD08-0BA8 for a 0BA8 with display and Ethernet).
4. Confirm with OK. The block palette refreshes; any block the target cannot run is greyed out.
5. Re-open the program. Blocks incompatible with the selected hardware now display a yellow exclamation mark.

Step 2 - Read the Device Firmware Version

1. Connect LOGO! Soft Comfort to the device via Ethernet or USB cable.
2. Choose LOGO! → Diagnostics → Device Information.
3. Record the FW version, Type, and Order number fields.
4. Compare the FW string with the table below.

If the device is 0BA6 and you need the native block, plan a hardware migration to 0BA7 or 0BA8 (catalog numbers listed above) before authoring new programs that depend on the Astro block.

Step 3 - Polynomial Regression Workaround for 0BA6

When the project must stay on 0BA6 hardware, derive sunrise and sunset minutes-from-midnight (local time) as two analog values that update once per day at 00:02 local. The reference implementation uses a 9th-degree Chebyshev polynomial fitted to NOAA solar position tables; coefficients are computed once in a spreadsheet and pasted into the LOGO! program as constants.

1. In Excel, compute sunrise_min(day_of_year, latitude) and sunset_min(day_of_year, latitude) using the SPA algorithm or NOAA's solpos model.
2. Fit two polynomials P_sunrise(d) and P_sunset(d) where d = (day_of_year - 1) / 365.
3. Truncate to degree 8 or 9; residual error below 90 s for π/3 < latitude < 5π/6 is typical.
4. Export coefficients c₀ ... c₈ as constants.
5. In LOGO! Soft Comfort for 0BA6, implement the polynomial with the Analog Math (B015) and Analog Multiplexer blocks chained:

y = c0 + c1*d + c2*d^2 + c3*d^3 + c4*d^4
      + c5*d^5 + c6*d^6 + c7*d^7 + c8*d^8 + c9*d^9

The single block diagram uses nine Analog Math instances, each adding one term; the cumulative sum drives an Analog Threshold Trigger (B007) compared to a real-time clock hour:minute value to switch the digital output Q1.

Step 4 - Native Solution: Migrate to LOGO! 0BA7 or 0BA8

1. Open the existing 0BA6 project in LOGO! Soft Comfort 8.x.
2. Press Ctrl+H, pick a 0BA8 catalog number (for example 6ED1052-1MD08-0BA8 for a 24 V DC, 8 DI / 4 DO, Ethernet variant).
3. The conversion wizard flags unsupported blocks; the Astro block on 0BA6 was a workaround, so it can be removed and replaced with B020 - Astronomical Clock.
4. Insert the Astro block and configure:
   • Latitude: signed decimal degrees, range -90 .. +90
   • Longitude: signed decimal degrees, range -180 .. +180 (East positive, West negative)
   • Time zone: offset in minutes from UTC, e.g. +60 for CET
   • DST: "EU", "US", or "Off" depending on region
5. Download to the new device. The Astro block delivers sunrise and sunset as digital outputs Q₁ and Q₂ of the block.

Astronomical Clock Block Parameters

Daylight Saving Time (DST) Handling on 0BA7 and 0BA8

The Astro block on 0BA7 firmware ES10 and later and on 0BA8 firmware FS:01 and later respects the DST rule set in the device. The clock block (B019) handles the actual hour step. If the LOGO! is set to "EU" DST but the application runs in a region with fixed UTC offset, set DST to Off and supply the local standard offset via the Time zone parameter.

Step 5 - Verification and Commissioning Checklist

1. After download, open LOGO! → Online Test and verify Q1 of the Astro block toggles within ±90 s of computed sunrise.
2. Compare the LOGO! on-screen sunset time against a reference (e.g. NOAA solar calculator) for the configured coordinates; deviation must stay below 2 minutes at solstice.
3. Force the time forward by 23:59 and observe the next day's transition; confirm the day-of-year counter advances and no rollover glitch occurs.
4. For the polynomial workaround, log the computed minutes-from-midnight via the LOGO! Data Log feature to a microSD card and verify against an Excel reference for at least three seasonal dates.
5. Power-cycle the LOGO! and confirm the sunrise/sunset schedule resumes without manual time re-entry.

Troubleshooting Matrix

Field-Proven Notes

Engineers porting 0BA6 polynomial programs to 0BA8 frequently observe the following:

• The Astro block on 0BA8 firmware FS:02+ honours leap seconds; 0BA6 firmware never tracks them, so long-running installations accumulate up to one minute of drift per decade.
• Battery-backed RTC on 0BA6 holds time for about 1 week without power; 0BA8 retains for up to 4 weeks. If the application loses power frequently, fit a fresh CR2032 backup cell before relying on Astro accuracy.
• Where the LOGO! is networked, enable NTP via the LOGO! CSK or a 4G router; the Astro block recalculates instantly on time correction, while the polynomial workaround still uses yesterday's day-of-year until 00:02.