Introduction
Incremental rotary encoders are essential components in modern automation and motion control systems. These devices measure:
- Rotational position
- Speed
- Direction of movement
Whether you’re working with:
- Industrial machinery
- Robotics
- CNC equipment
- DIY electronics projects
Understanding incremental encoders will help you choose and use them effectively.
How Incremental Encoders Work
Basic Operation Principle
Incremental encoders generate pulse signals as the shaft rotates. Unlike absolute encoders, they:
✔ Only track movement (not absolute position)
✔ Require a reference point (index pulse)
✔ Provide two square-wave signals (A and B channels) 90° out of phase
Key Components
- Code disc: Patterned disk that interrupts light
- LED light source: Creates optical signals
- Photodetector: Reads light patterns
- Signal processor: Converts to digital output
Incremental vs. Absolute Encoders
| Feature | Incremental Encoder | Absolute Encoder |
|---|---|---|
| Position Tracking | Relative movement only | Exact position always known |
| Power Loss | Requires homing | Retains position |
| Complexity | Simpler design | More complex |
| Cost | More affordable | More expensive |
| Best For | Speed measurement | Position-critical applications |
Types
1. Optical Encoders
✔ Highest resolution available
✔ Excellent accuracy
✖ Sensitive to contamination
2. Magnetic Encoders
✔ Durable in harsh environments
✔ Resistant to dust/moisture
✖ Lower resolution than optical
3. Mechanical Encoders
✔ Most affordable option
✔ Simple construction
✖ Limited lifespan (contact wear)
Top 5
1. Omron E6B2-CWZ6C (Optical)
✔ Pros:
- 2000 PPR resolution
- IP50 dust protection
- Reliable performance
✔ Cons: - Not waterproof
- Requires careful handling
Best for: Industrial automation
2. Bourns EMS22A (Magnetic)
✔ Pros:
- 512 CPR resolution
- Rugged construction
- Wide temperature range
✔ Cons: - Lower resolution than optical
- More expensive than basic models
Best for: Harsh environments
3. Autonics E40S (Compact Optical)
✔ Pros:
- Small form factor
- 100-5000 PPR options
- Cost-effective
✔ Cons: - Limited environmental protection
- Basic features only
Best for: DIY projects and small machines
4. Hengstler RI 58 (Heavy-Duty)
✔ Pros:
- Industrial-grade durability
- Up to 10,000 PPR
- Multiple output options
✔ Cons: - Large size
- Premium price
Best for: CNC and high-precision applications
5. US Digital E2 (Budget Optical)
✔ Pros:
- Affordable price
- 100-2000 CPR options
- Easy to interface
✔ Cons: - Basic protection only
- Limited resolution options
Best for: Hobbyists and education
Key Specifications Explained
1. Resolution (PPR/CPR)
- Pulses/Counts per Revolution
- Higher numbers = more precision
- Typical range: 100-10,000 PPR
2. Output Signals
- Quadrature (A/B channels): Standard for direction detection
- Index (Z channel): Reference pulse per revolution
- Output types: TTL, HTL, RS422
3. Mechanical Specifications
- Shaft type (solid/hollow)
- Bearing quality
- Maximum RPM rating
4. Environmental Protection
- IP ratings for dust/water resistance
- Temperature range
- Vibration tolerance
Incremental Encoder Buying Guide
1. Determine Your Resolution Needs
- Basic motion detection: 100-500 PPR
- Precision control: 1000-5000 PPR
- High-end applications: 5000+ PPR
2. Choose the Right Technology
- Clean environments: Optical for best accuracy
- Dusty/moist areas: Magnetic for durability
- Budget projects: Mechanical (with shorter lifespan)
3. Consider Output Requirements
- Microcontroller projects: TTL output
- Industrial PLCs: HTL or RS-422
- Long cable runs: Differential outputs
4. Environmental Factors
- IP rating needed?
- Temperature extremes?
- Vibration exposure?
5. Mounting Options
- Shaft size compatibility
- Through-bore vs. solid shaft
- Flange mounting requirements
Installation and Wiring Tips
Basic Connection Guide
- Power supply (typically 5V or 12V)
- Channel A output
- Channel B output
- Index/Z channel (if used)
- Ground connection
Common Pitfalls to Avoid
- Incorrect voltage supply
- Poor cable shielding (noise issues)
- Mechanical misalignment
- Exceeding maximum RPM
Personal Experience: Choosing Encoders for CNC
When building my CNC router, I initially chose a cheap mechanical encoder. The problems I encountered:
- Rapid wear from continuous use
- Lost steps during high-speed movements
- Inconsistent performance
Switching to an Omron optical encoder solved these issues immediately. The higher resolution (2000 PPR) provided smoother operation, and the reliability improved my machine’s accuracy dramatically.
For my 3D printer project, I used a US Digital E2 – the affordable price and easy Arduino compatibility made it perfect for this application.
Incremental Encoder FAQs
Q: How do I determine direction with an incremental encoder?
A: By monitoring the phase relationship between A and B channels (which signal leads determines direction).
Q: What’s the difference between PPR and CPR?
A: PPR (Pulses Per Revolution) counts physical marks, while CPR (Counts Per Revolution) includes electronic multiplication.
Q: Do incremental encoders need special drivers?
A: Most microcontrollers can read them directly, though some high-speed applications benefit from dedicated encoder interface chips.
Q: Can I replace an absolute encoder with an incremental one?
A: Only if your system can handle the homing routine required after power loss.
Q: How long do incremental encoders typically last?
A: Optical encoders: 50,000+ hours; Magnetic: 100,000+ hours; Mechanical: 10,000-50,000 cycles.
Future Trends in Encoder Technology
Emerging developments to watch:
- Integrated smart sensors with built-in diagnostics
- Higher resolutions in compact packages
- Wireless encoder options
- Improved durability for extreme environments
Final Recommendations
For industrial use, Omron or Hengstler optical encoders offer the best reliability.
For harsh environments, Bourns magnetic encoders provide excellent durability.
For hobbyists, US Digital or Autonics offer great value for money.
Remember to match your encoder to your specific requirements for resolution, environment, and interface needs.
Read More: rotary optical encoder
