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Control Signals for 3-Position Pneumatic Actuators
To operate a 3-position pneumatic actuator (Open-Neutral-Close), the following control signals are typically required:
1. Electrical Control Signals
Digital (On/Off) Control:
- Two solenoid valves (e.g., 5/3-way) – one for each direction (Open/Close)
- 24V DC or 120V AC power supply for coil energization
Analog (Proportional) Control:
- 4–20mA or 0–10V signal to regulate pressure via I/P converter or proportional valve
2. Pneumatic Signals
- Dual air supply lines (typically 4–6 bar) for bidirectional movement
- Balanced pressure (equal pressure on both sides) to hold the neutral position
3. Feedback & Positioning Signals
- Limit switches (for digital position confirmation)
- Potentiometer or encoder (for analog position feedback in closed-loop systems)
4. PLC/Controller Interface
- Discrete I/O (for solenoid control)
- Analog I/O (for proportional positioning)
- Fieldbus protocols (PROFIBUS, Modbus) for smart actuators
Applications:
- Process control (throttling, mixing)
- Safety systems (fail-neutral positions)
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