PCB สำหรับระบบอัตโนมัติในโรงงาน: คู่มือ PLC, Motor Drive และ Sensor Integration

# PCB สำหรับระบบอัตโนมัติในโรงงาน: คู่มือฉบับสมบูรณ์

อุตสาหกรรม Industrial Automation มูลค่ากว่า 200 พันล้านดอลลาร์ เป็นกระดูกสันหลังของ Industry 4.0 PCB สำหรับ automation ต้องทำงานใน harsh environment, มี reliability สูงมาก, และทนทานต่อ EMI/EMC ที่รุนแรง

> จากประสบการณ์โรงงาน: "Industrial automation PCB ต้อง design for reliability ไม่ใช่แค่ function เพราะถ้า PLC ล่มสายการผลิตทั้งหมดหยุด ความเสียหายวันละล้านบาทได้ เราต้องคิดเรื่อง MTBF ตั้งแต่วันแรกของ design" — Hommer Zhao, Engineering Director

---

สารบัญ

1. Industrial Automation Overview
2. PLC Design
3. Motor Drive & VFD
4. Sensor Interface
5. Industrial Communication
6. Power Supply Design
7. Harsh Environment
8. EMC & Safety
9. Reliability & Testing
10. Case Studies

---

1. Industrial Automation Overview {#overview}

Market Landscape

```

Industrial Automation PCB Market 2024

═══════════════════════════════════════════════════════════

By Product Type:

├── PLC/PAC ██████████████ 28% ($56B)

├── Motor Drives/VFD ████████████ 24% ($48B)

├── Industrial Sensors ██████████ 20% ($40B)

├── HMI/Displays ██████ 12% ($24B)

├── Industrial PC ████ 8% ($16B)

└── Others ████ 8% ($16B)

By Industry:

├── Automotive manufacturing - 25%

├── Food & Beverage - 18%

├── Packaging - 15%

├── Semiconductor - 12%

├── Oil & Gas - 10%

└── Others - 20%

Growth: 8-10% CAGR (Industry 4.0 driven)

═══════════════════════════════════════════════════════════

```

Key Requirements Comparison

---

2. PLC Design {#plc}

PLC Architecture

```

Modern PLC System Architecture

═══════════════════════════════════════════════════════════

┌────────────────────────────────────────────────────┐

│ BACKPLANE │

│ ┌─────────┬─────────┬─────────┬─────────────┐ │

│ │ Power │ CPU │ I/O │ Comm │ │

│ │ Supply │ Module │ Modules │ Modules │ │

│ └────┬────┴────┬────┴────┬────┴──────┬──────┘ │

│ │ │ │ │ │

│ ┌────┴─────────┴─────────┴───────────┴────┐ │

│ │ System Bus │ │

│ │ Power + Data + High-speed Backplane │ │

│ └──────────────────────────────────────────┘ │

└────────────────────────────────────────────────────┘

CPU Module (typical 4-6 layer):

┌────────────────────────────────────┐

│ ┌─────────────────────────────┐ │

│ │ Processor (ARM/x86) │ │

│ │ + Memory (DDR3/4) │ │

│ └─────────────────────────────┘ │

│ │

│ ┌──────────┐ ┌──────────────┐ │

│ │ RTC/NVRAM│ │ Comm Bridge │ │

│ └──────────┘ │ (FPGA/ASIC) │ │

│ └──────────────┘ │

│ │

│ ┌──────────────────────────────┐ │

│ │ Backplane Connector │ │

│ └──────────────────────────────┘ │

└────────────────────────────────────┘

═══════════════════════════════════════════════════════════

```

I/O Module Design

PLC PCB Design Guidelines

```

PLC Module Design Checklist

═══════════════════════════════════════════════════════════

□ Isolation Design

├── Digital isolation (optocoupler/digital isolator)

├── Analog isolation (transformer coupled)

├── Creepage/clearance per IEC 61131-2

└── Ground plane splits

□ I/O Protection

├── TVS diodes on all inputs

├── Polyfuse or PTC on outputs

├── ESD protection to ±15kV

└── Reverse polarity protection

□ EMC Design

├── Filtered connectors

├── Common mode chokes

├── Guard rings around sensitive circuits

└── 360° shield grounding

□ Thermal Design

├── Heat spreading layers

├── Thermal vias under hot components

├── Natural convection optimization

└── No fans (maintenance concern)

═══════════════════════════════════════════════════════════

```

---

3. Motor Drive & VFD {#motor-drive}

VFD Power Stage

```

Variable Frequency Drive Architecture

═══════════════════════════════════════════════════════════

AC Input Rectifier DC Link Inverter Motor

(3-phase) (3-phase)

│ ┌─────┐ ┌─────┐ ┌─────┐ │

────┼───────────┤ ├─────┤ ├──────┤ ├────────┼────

L1 │ │ │ │ │ │ │ U │

────┼───────────┤ AC │ │ DC │ │ ├────────┼────

L2 │ │ to │ │ Bus │ │ │ V │

────┼───────────┤ DC │ │ │ │ DC ├────────┼────

L3 │ │ │ │ │ │ to │ W │

│ └─────┘ └─────┘ │ AC │ │

│ │ │ │ │

│ ┌────────────┴─────┐ └─────┘ │

│ │ DC Bus Caps │ │ │

│ │ (Film caps) │ │ │

│ └──────────────────┘ │ │

│ │ │

└─────────────────────────────────────────┴─────────┘

│

┌─────┴─────┐

│ Control │

│ Board │

│ (DSP/MCU) │

└───────────┘

PCB Separation:

├── Power board (high voltage, high current)

├── Gate driver board (interface)

└── Control board (low voltage logic)

═══════════════════════════════════════════════════════════

```

Power PCB Requirements

Gate Driver Design

```

Gate Driver PCB Layout

═══════════════════════════════════════════════════════════

Critical Layout Rules:

┌─────────────────────────────────────────────────────┐

│ │

│ ┌──────────┐ ┌──────────────────────┐ │

│ │ Gate │◄────────┤ Decoupling Caps │ │

│ │ Driver │ │ (100nF//10μF) │ │

│ │ IC │ │ <5mm from IC │ │

│ └────┬─────┘ └──────────────────────┘ │

│ │ │

│ │ Gate line: short, wide, minimize Lg │

│ │ │

│ ▼ │

│ ┌─────────────────────────────────────────┐ │

│ │ IGBT/MOSFET Gate Pin │ │

│ │ Kelvin source connection │ │

│ └─────────────────────────────────────────┘ │

│ │

│ Return path: │

│ ├── Separate Kelvin source pin │

│ ├── Low inductance return │

│ └── Avoid common impedance │

│ │

└─────────────────────────────────────────────────────┘

Key Parameters:

├── Gate loop inductance: <10nH

├── Miller capacitance handling

├── dv/dt immunity: >50V/ns

└── Isolation: 1500Vrms or higher

═══════════════════════════════════════════════════════════

```

---

4. Sensor Interface {#sensor}

Industrial Sensor Types

```

Common Industrial Sensors & Interfaces

═══════════════════════════════════════════════════════════

┌──────────────────┬─────────────┬──────────────────────┐

│ Sensor Type │ Interface │ PCB Considerations │

├──────────────────┼─────────────┼──────────────────────┤

│ Proximity │ PNP/NPN │ ESD protection │

│ (Inductive) │ 10-30VDC │ Surge handling │

├──────────────────┼─────────────┼──────────────────────┤

│ Temperature │ 4-20mA │ EMI filtering │

│ (RTD/TC) │ 0-10V │ Cold junction comp │

├──────────────────┼─────────────┼──────────────────────┤

│ Pressure │ 4-20mA │ Isolation │

│ (Strain gauge) │ RS485 │ Precision routing │

├──────────────────┼─────────────┼──────────────────────┤

│ Flow │ Pulse │ High-speed capture │

│ (Turbine) │ 4-20mA │ Pulse conditioning │

├──────────────────┼─────────────┼──────────────────────┤

│ Vision/Camera │ GigE/USB3 │ Impedance matching │

│ │ Camera Link │ High-speed routing │

├──────────────────┼─────────────┼──────────────────────┤

│ Encoder │ RS422 diff │ Noise immunity │

│ (Rotary) │ SSI/BiSS │ High-speed digital │

└──────────────────┴─────────────┴──────────────────────┘

═══════════════════════════════════════════════════════════

```

4-20mA Loop Design

---

5. Industrial Communication {#communication}

Fieldbus Comparison

```

Industrial Communication Standards

═══════════════════════════════════════════════════════════

Protocol Speed Distance Topology Adoption

──────────────────────────────────────────────────────────

PROFINET 100Mbps 100m Star/Line ████████ High

EtherNet/IP 100Mbps 100m Star/Ring ███████ High

EtherCAT 100Mbps 100m Line ██████ High

PROFIBUS-DP 12Mbps 1200m Bus ██████ Legacy

Modbus RTU 115kbps 1200m Bus ████ Common

DeviceNet 500kbps 500m Bus ███ Legacy

CANopen 1Mbps 40-500m Bus ████ Growing

CC-Link IE 1Gbps 100m Star ███ Japan

PCB Requirements:

├── Ethernet-based: RJ45 + magnetics + PHY

├── RS485-based: Transceiver + termination

├── CAN-based: CAN controller + transceiver

└── All: ESD protection, isolation optional

═══════════════════════════════════════════════════════════

```

Ethernet PHY Layout

```

Industrial Ethernet PCB Layout

═══════════════════════════════════════════════════════════

┌────────────────────────────────────────────────────┐

│ │

│ ┌─────────┐ ┌──────────┐ ┌─────────────┐ │

│ │ MAC │◄──►│ PHY │◄──►│ Magnetics │◄─┼─► RJ45

│ │ (CPU) │ │ (RMII) │ │ (Bob Smith │ │

│ └─────────┘ └──────────┘ │ center tap)│ │

│ └─────────────┘ │

│ │

│ Layout Rules: │

│ ├── PHY to Magnetics: <25mm │

│ ├── Differential pairs: 100Ω ±10% │

│ ├── Tight length matching: <5mm │

│ ├── Reference plane unbroken │

│ └── ESD protection near RJ45 │

│ │

│ Industrial Additions: │

│ ├── M12 connector option │

│ ├── IP67 sealed RJ45 │

│ ├── 1500V port isolation (optional) │

│ └── Surge protection (gas discharge + TVS) │

│ │

└────────────────────────────────────────────────────┘

═══════════════════════════════════════════════════════════

```

RS485 Design

---

6. Power Supply Design {#power}

Industrial Power Architecture

```

Industrial Power Supply Architecture

═══════════════════════════════════════════════════════════

AC Input (85-264VAC)

│

▼

┌──────────────┐

│ EMI Filter │ ← Common mode + differential mode

│ + Inrush │

└──────┬───────┘

│

▼

┌──────────────┐

│ PFC Stage │ ← Active PFC (CCM or CrM)

│ (Boost) │ PF>0.95, THD<10%

└──────┬───────┘

│

│ 380-400VDC bus

▼

┌──────────────┐

│ Isolated │ ← LLC or flyback

│ DC-DC │ Efficiency >90%

└──────┬───────┘

│

│ 24VDC (main rail)

▼

┌──────────────┐

│ POL │ ← Buck converters

│ Regulators │ 5V, 3.3V, 1.8V, etc.

└─────────────┘

Protection Features:

├── OVP/UVP (input and output)

├── OCP/OPP (current/power limiting)

├── OTP (thermal shutdown)

├── Short circuit protection

└── Inrush current limiting

═══════════════════════════════════════════════════════════

```

24VDC Industrial Standard

---

7. Harsh Environment {#environment}

Environmental Challenges

```

Industrial Environment PCB Challenges

═══════════════════════════════════════════════════════════

Temperature:

├── Ambient: -40°C to +85°C

├── Internal rise: +30-50°C

├── Thermal cycling stress

└── Solution: Wide temp components, thermal management

Humidity:

├── 10-95% RH non-condensing

├── Condensation risk

├── Electrochemical migration

└── Solution: Conformal coating, proper spacing

Vibration:

├── 5-500Hz, 2-10G

├── Random and sine vibration

├── Shock: 15-50G

└── Solution: Secure mounting, no tall components

Contamination:

├── Dust (IP6X)

├── Oil mist

├── Chemical vapors

├── Solution: Sealed enclosure, PTFE coating

EMI Environment:

├── VFD switching noise

├── Motor inrush

├── Welding transients

└── Solution: Shielding, filtering, isolation

═══════════════════════════════════════════════════════════

```

Conformal Coating Options

---

8. EMC & Safety {#emc}

EMC Standards

```

Industrial EMC Requirements

═══════════════════════════════════════════════════════════

Emission Standards (Must Not Interfere):

├── IEC 61000-6-4 (Generic industrial emissions)

├── EN 55011/32 (Equipment class)

└── FCC Part 15 Class A

Immunity Standards (Must Withstand):

├── IEC 61000-6-2 (Generic industrial immunity)

├── IEC 61000-4-2: ESD ±8kV contact, ±15kV air

├── IEC 61000-4-3: Radiated immunity 10V/m

├── IEC 61000-4-4: EFT/Burst ±2kV

├── IEC 61000-4-5: Surge ±2kV line-to-line

├── IEC 61000-4-6: Conducted immunity 10V

└── IEC 61000-4-11: Voltage dips/interrupts

PCB Design Countermeasures:

├── EMI: Filtering, shielding, proper grounding

├── ESD: TVS diodes, guard rings, air gaps

├── EFT: Decoupling, ferrites, proper layout

└── Surge: MOVs, TVS, isolation, spacing

═══════════════════════════════════════════════════════════

```

Safety Standards

> Safety First: "Industrial equipment ต้องผ่าน safety certification เสมอ ไม่ว่าจะเป็น CE, UL หรือ TÜV การออกแบบ PCB ต้องคำนึงถึง creepage, clearance, และ isolation ตั้งแต่ต้น แก้ทีหลังแพงมาก" — Hommer Zhao

---

9. Reliability & Testing {#reliability}

MTBF Calculation

```

MTBF Estimation for Industrial PCB

═══════════════════════════════════════════════════════════

Calculation Method (MIL-HDBK-217F):

λ_total = Σ(λ_component × π_factors)

Component Failure Rates (per billion hours):

├── Capacitor (ceramic): 5-50

├── Capacitor (electrolytic): 100-500

├── Resistor (chip): 1-10

├── IC (digital): 50-200

├── IC (analog): 100-300

├── Connector: 10-50

├── PCB (per cm²): 0.1-1

└── Solder joints: 0.1-5 each

π Factors:

├── Temperature: 1-10× (higher temp = higher rate)

├── Environment: 1-20× (industrial = higher)

├── Quality level: 0.5-2×

└── Stress: 1-5× (higher current/voltage = higher)

Target MTBF:

├── Safety controller: >200,000 hours

├── Standard PLC: >100,000 hours

├── Motor drive: >50,000 hours

└── General I/O: >100,000 hours

═══════════════════════════════════════════════════════════

```

Testing Requirements

---

10. Case Studies {#cases}

Case 1: Motor Drive Control Board

```

Project: 75kW VFD Control Board

═══════════════════════════════════════════════════════════

Challenge:

├── High dv/dt from IGBT switching (10kV/μs)

├── EMI coupling to control circuits

├── Operating temp: 0 to +55°C ambient

└── Required MTBF: >50,000 hours

Design Solution:

├── 4-layer PCB with dedicated ground plane

├── Gate driver isolation: 2.5kV

├── Control/power ground star topology

├── Shielded connectors all interfaces

├── Conformal coating (silicone)

└── Heavy copper (3oz) for power paths

Results:

├── EMC: Passed IEC 61800-3 Category C2

├── MTBF: Calculated 85,000 hours

├── Operating temp: -10 to +60°C verified

└── Field return rate: <0.3% in 3 years

═══════════════════════════════════════════════════════════

```

Case 2: Industrial IoT Gateway

Case 3: Safety PLC Module

```

Project: SIL2 Safety Controller

═══════════════════════════════════════════════════════════

Requirements:

├── SIL2 (Safety Integrity Level 2)

├── IEC 61508 compliance

├── Dual-channel architecture

├── Self-diagnostics >99% DC

└── MTBF >200,000 hours

Design Features:

├── Redundant processors

├── Cross-checking between channels

├── Watchdog on each channel

├── Safe state on any failure

├── Galvanic isolation between channels

└── Separate power domains

PCB Design:

├── 6-layer board

├── Separated zones per channel

├── Careful routing to prevent common cause

├── Enhanced creepage (2× standard)

└── 100% tested production

Certification:

├── TÜV SÜD certified SIL2

├── UL 508 / EN 61010

└── CE marking complete

═══════════════════════════════════════════════════════════

```

---

บริการของเรา

PCB Thailand เชี่ยวชาญการผลิต PCB สำหรับ Industrial Automation:

• FR-4 PCB - Standard และ high-Tg
• Aluminum PCB - Power applications
• Turnkey Assembly - ครบวงจร

> Industrial Experience: "เราทำงานกับลูกค้า automation มากว่า 10 ปี เข้าใจ requirements เฉพาะทาง ทั้ง EMC, safety standards, และ reliability targets ทีมเราพร้อมให้คำปรึกษาตั้งแต่ design stage" — Hommer Zhao

ขอใบเสนอราคา สำหรับโปรเจค Industrial ของคุณ

---

บทความที่เกี่ยวข้อง

• DFM Guidelines
• EMC Design
• Thermal Management