Siemens LOGO! Multi-Setpoint Dispensing with Analog MUX

Siemens LOGO! Multi-Setpoint Dispensing with Analog MUX and High-Speed Counter

Volumetric dispensing applications such as drink pourers, dosing skids, and small-batch fillers share a common control pattern: a single flow sensor must stop a solenoid after one of several preset volumes has been delivered. On a Siemens LOGO! 8 base module (6ED1052-1xxx08-0BA1 series), this pattern collapses to one High-Speed Counter block, one Analog Multiplexer (MUX) block, and one On-Delay for debounce — replacing the three separate timers commonly used in beginner code. This reference walks through the complete implementation, from flow-meter pulses per litre to LOGO! Web Server custom-quantity entry.

1. Application Overview

The reference application is a three-size beer pourer on a bar top. The bartender selects a size (0.25 cl, 0.50 cl, or 1.00 l) and a quantity (5, 10, 15 units, or any value entered through the LOGO! Web Server). The program commands a 24 V DC solenoid valve open, accumulates flow-sensor pulses on the high-speed counter, and de-energises the coil when the active setpoint is reached.

2. Prerequisites

• Base module: LOGO! 8.3 — catalog 6ED1052-1MD08-0BA1 (24 V DC powered, 8 DI / 4 DQ, with display) or 6ED1052-2MD08-0BA1 (with Ethernet). The high-speed counter is available on all LOGO! 8 BM variants.
• Software: LOGO! Soft Comfort V8.3 (6ED1058-0BA08-0YA1) for circuit-diagram programming and Web Server configuration.
• Firmware: BM with FS ≥ 04 (for V2.0 Web Server, custom-quantity text boxes are supported on FS ≥ 04).
• Flow sensor: PNP/NPN pulse output, ≥ 100 pulses per litre, 24 V DC. A gear-meter such as Gems Sensors FT-110 series or ifm efector SU7 typically delivers 1000–5000 pulses/litre.
• Solenoid valve: 24 V DC, ≤ 0.5 A continuous, with surge suppression (free-wheel diode across coil).
• Power supply: 24 V DC, ≥ 1.5 A derated, regulated.

3. Wiring Topology

Wire the flow sensor's signal output to I3, with the common return to the LOGO! 24 V DC negative terminal. The solenoid is wired between +24 V and Q1; a 1N4007 fly-back diode (cathode to +24 V) is mandatory to protect the LOGO! output stage from inductive kick.

4. Pulse-to-Volume Calibration

The high-speed counter counts raw pulses; the On threshold on the counter must be expressed in pulses, not in litres. Define a Pulse Factor P_f = pulses per litre, measured by dispensing 1.0 l of beer into a graduated cylinder and noting the count.

For a target volume V in litres, the setpoint in pulses is:

S_p = round(V × P_f)

5. LOGO! Soft Comfort Program Structure

The complete program uses seven blocks. Open LOGO! Soft Comfort V8.3, choose a new circuit, then add the blocks below in the order shown.

5.1 High-Speed Counter Configuration (B10)

From the block library, drag Special → Counter → High-Speed Counter (B10 in V8.3). Configure as follows:

5.2 Analog Multiplexer Configuration (B18)

The Analog MUX (B18) is the single block that lets one HSC threshold serve three size setpoints. Wire the four numeric constant inputs to the calibrated pulse values and the selector bits to the size inputs.

S1 and S2 are derived from the input bits by an OR-AND pre-stage (or by the simpler trick of feeding the inputs directly and adding a small OR with the next-higher bit so a single size button drives the correct MUX address without combinatorial hazards).

5.3 Quantity Multiplier

The Up/Down Counter (B4) accumulates number of shots. A second small Analog MUX (B18 again) multiplies the per-shot setpoint by the requested quantity before it is passed to the HSC threshold. For pour quantity N, the scaled setpoint is:

SP_total = SP_one × N

For a 1 l mass (4500 pulses) poured 15 times the HSC must count to 67 500. The HSC B10 counter is a 32-bit counter on LOGO! 8, so this is within range. If the application requires > 2 million pulses, switch the integrator to a regular Up Counter and use a comparator to gate the HSC reset.

5.4 Solenoid Latch (RS Flip-Flop)

Use the RS Latch (B3) so the button press arms the cycle:

• S (set): I1 (start button) rising edge
• R (reset): Output of the comparator (HSC.CN ≥ SP_total)
• Q: drives Q1 (solenoid) and Q2 (status LED) in parallel

The HSC is also reset on the same comparator rising edge through an Edge-Triggered Reset (B11), preparing the system for the next shot.

6. LOGO! Web Server — Custom Quantity Entry

Enable the Web Server in Tools → Web Server in LOGO! Soft Comfort. The default 0BA8 BM has the V1.0 Web Server; the 8.3 (FS04) BM ships the V2.0 Web Server with the Web Editor for desktop browsers.

1. Open Tools → Web Editor, drag a Text field onto the operator page.
2. Bind the field to a network input, e.g. NI1, with integer type and range 1–99.
3. Link NI1 in the LOGO! program to a numeric constant block whose output drives the second Analog MUX's N input.
4. Add two further text fields bound to AQ1 (active setpoint in pulses) and AM2 (real-time HSC count) for operator feedback.
5. Compile and download. Browse to http://<LOGO-IP> and authenticate with the user name LOGO and the password configured under Tools → Web Server → Access Control.

7. Step-by-Step Commissioning Procedure

1. Verify I/O. In LOGO! Soft Comfort's online mode, force Q1 and confirm the solenoid click and the flow-sensor pulse stream on I3 (use a scope on a digital input, or the Watch Table with HSC.CN incrementing).
2. Calibrate the flow sensor. Manually latch Q1 for 30 seconds, capture CN at the end, and divide by the dispensed litre count to compute P_f. Replace the constants in the MUX with the measured values.
3. Single-shot check. Press I1 with the 0.25 cl size selected (I5). The solenoid should de-energise within 1  pulse of the calibrated setpoint. Repeat 20 times; record the poured volume; verify < ±2% deviation.
4. Multi-shot check. Repeat with quantity = 15 (I8) on the 1 l size. Confirm the HSC threshold now reads 67 500 and the system delivers 15 discrete shots.
5. Web Server check. Connect to the LOGO! IP, enter a custom quantity of 7, and verify NI1 in the online watch table. Re-run a single 1 l pour with N=7; total pulses should be 7 × 4500 = 31 500.
6. Edge cases:
   • Pressing I1 while no size is selected should be ignored (MUX output = 0, comparator never trips → safety lockout).
   • Loss of I3 pulses (sensor unplugged) should be detected by a 5 s watchdog that de-energises Q1 and triggers Q3 (fault output).

8. Verification Matrix

9. Troubleshooting Matrix

10. Extending the Reference

The same Analog MUX pattern scales linearly. For four sizes, promote the MUX to an 8-input variant (B17 analog multiplexer) and reserve a fourth selector bit. For temperature-compensated dispensing (cold beer is denser → more pulses per litre), feed the MUX selector a Gain block whose input is a PT100 or thermistor analogue input; the setpoint S_p is then multiplied by the calibrated density factor in real time.

For wash-down environments, replace the LOGO! BM with a SIP65 variant (6ED1052-1MD08-0BA1 with conformal coating) or relocate the LOGO! to a control panel and bring only the inputs/outputs out to IP65 push-buttons.

11. Notes on Standards and Sizing

The 24 V DC solenoid sizing assumes a steady-state current below the LOGO! 8 DQ rating of 0.3 A continuous (transistor outputs) or 5 A (relay outputs on -1HF08 variants). For inductive loads, confirm the suppression diode reverse-voltage rating is ≥ 2 × supply, and the surge current rating is ≥ 1 A. Always verify the applicable beverage-dispensing local code (e.g. NSF/ANSI 18 for manual food and beverage dispensing equipment, IEC 60204-1 for general machinery safety) and provide an Emergency-Stop hardwired circuit independent of the LOGO!.

12. Reference Resources

The official Siemens LOGO! system manual documents every block, every threshold parameter, and every Web Server field used above. For commissioning support, the Siemens Industry Online Support portal hosts the LOGO! application examples library and the LOGO! Web Server kit.