Understanding whether you need an encoder for your optical scanner is a critical question in the design process—one that we often explore with our customers at Waterloo Optics. The answer hinges on how crucial it is to know the scanner’s position at any given time.
Types of Encoders: A Quick Overview
- Absolute Encoders: When queried, these devices report the exact angle or position of your optical scanner. Communication is typically handled via digital protocols like the Serial Peripheral Interface (SPI), ensuring precise, real-time data.
- Incremental Encoders: These encoders detect and report each tiny shift in your scanner’s position as it rotates. For instance, using quadrature encoding, our scanners can distinguish every slight rotation, providing detailed feedback on speed, position, and acceleration through multiple output signals.
Incremental Quadrature Encoding: A Closer Look
Our most utilized method in optical scanners is incremental quadrature encoding. This technique provides:
- Index Signal: Occurs once per rotation, marking a clear reference point for the scanner’s position.
- A and B Channels: These signals occur multiple times per rotation. By analyzing the phase relationship between A and B, the direction of rotation can be deduced, while monitoring the cycles of the channels allows one to determine the precise speed and positioning.
The diagram shown here illustrates the channels of an incremental encoder. The number of output cycles that each channel outputs may be specified, such as 256, 1024, etc. For example, in a 1024 cycle encoder, Channel A will output 1024 cycles per revolution (CPR). Channels B will output 1024 cycles per revolution (CPR). The diagram show a cycle as “C”. Measured together, in quadrature, yields 4096 measurement events per revolution (voltage rise or voltage fall being a measurement event). The index channel I produces one pulse per revolution.
When You Might Not Need an Encoder
Opting out of using an encoder is also a viable strategy. For example, by integrating a single pole pair brushless DC motor in your design, the hall sensors themselves can act as index signals, simplifying the system while still providing the ability to estimate position based on speed and elapsed time.
Choosing the Right Encoder Technology
At Waterloo Optics, we specialize in both optical and magnetic encoder technologies:
- Optical Encoders: Offer superior precision and are ideal for controlled environments. May be susceptible to interference from dust or humidity if present.
- Magnetic Encoders: Robust against environmental conditions but can be sensitive to magnetic interference.
Let’s Make Your Scanner Stand Out
Every application is unique, and so should be your solution. Whether you’re dealing with a polygon or monogon scanner, our team at Waterloo Optics is dedicated to ensuring your project not only meets but exceeds expectations. Contact us today to discover how our tailored solutions can enhance your product’s performance and reliability.