Panel Mount Encoders
C14 and ACZ Series



Introduction

Welcome to the CUI Product Spotlight on panel mount encoders. Learn about CUI's C14 and ACZ panel mount encoder series, including their applications, specifications and the available products in CUI's broad line of encoders.

Objectives

  • To explain how panel mount rotary encoders fundamentally work and provid definitions to key specification and principles
  • Describe the difference between mechanical and optical encoder technology
  • Describe the key features of CUI's ACZ and C14 series
  • Detail typical applications in which these encoders are used

What are Encoders?

There are many types of encoders. In this product spotlight we will focus on rotary encoders. Rotary encoders can be defined as transducers designed to turn a rotational displacement into an electrical signal which can be read by a microprocessor.

  • Encoders are a type of sensor designed to provide rotation information
  • An encoder sends out a pulse each time it is moved a certain number of degrees
  • A microprocessor counts these pulses and calculates rotation

What are Panel Mount Encoders?

Panel mount encoders are a type of rotary encoder. They are primarily used for human interface purposes, i.e., a volume knob on a stereo. They give the user the ability to control various system parameters by providing the link between the user and the system processor.

  • Panel mount encoders are designed for use in human interface applications
  • They provide an accurate and inexpensive method for user manipulation of electronic products

Why an Encoder?

Panel mount rotary encoders are rapidly gaining popularity over potentiometers which are the other, major panel mount components used to translate rotational movement into a readable signal. The first advantage that encoders offer over potentiometers is consistency. Potentiometer manufacturing tolerances are large, leading to inconsistencies between units in the same batch. Accuracy is tied to consistency. Secondly, digital outputs are more compatible with today's digital devices and require no analog to digital converters, reducing cost and preventing errors.

Digital (Encoders):

  • Consistent
  • Accurate
  • Digital

Analog (Potentiometers):

  • Inconsistent
  • Accuracy is hardware dependent
  • Analog

Applications

Panel mount encoders are used in many applications across numerous industries, including defense & aerospace, medical, consumer goods, and test & measurement to name a few

Defense & Aerospace

  • Simulators, cockpit control
  • Handheld, mobile, fixed radios
  • Ground control, weapon control
  • Marine applications

Rescue & Security

  • CCTV (closed circuit TV)
  • Handheld, mobile, fixed radios
  • Rescue tools and equipment


Light & Sound

  • Studio mixers and cutting
  • PA and on-stage equipment
  • On-site transmission equipment


Infrastructure Control

  • Traffic control for car, railway
  • Traffic information systems
  • Power plant and energy distribution
  • Communication network control

Research & Science

  • Electronic lab and instrumentation
  • Meteorology and geology measures
  • Petro and pharmaceutical measures
  • Other physical measures

Industrial Automation

  • Motor drives
  • PLCs and control systems
  • Remote control units
  • Tooling machines

Transportation Vehichle

  • Construction machinery cockpits
  • Remote control for construction
  • Rail car and ship cockpits
  • Car side passenger information

Building & Facilities

  • Heater and air conditioning
  • Lock and access systems
  • Remote control units
  • Illumination control

Consumer

  • Audio equipment/home entertainment
  • White goods (Washer/Dryer)
  • Espresso machine
  • Fitness and wellness equipment

Medical

  • Surgery tools
  • Analysis devices
  • X-ray, ultrasonic and MRI
  • Life recovery and sustainment

Key Specifications

There are several key specifications to consider when talking about rotary encoders. PPR (pulses per revolution) determines the encoder's resolution, which is defined as the number of square wave pulses per 360 degree rotation of the encoder. Additionally, we define PPR as the number of low to high transitions per channel per revolution. Occasionally, an encoder's resolution is specified as CPR (counts per revolution), which is simply the number of quadrature state changes per revolution, CPR= PPR x 4.

Detents are useful in providing feedback to the user by “clicking” into place as the shaft is rotated. Detents are specified as the number of clicks per 360 degree rotation.

The push switch feature simply provides another user input signal. It is often used to select the function to be manipulated by turning the encoder knob.

  • PPR (pulses per revolution) - The number of square wave pulses per revolution of the encoder shaft per channel, this measure is also known as “resolution”
  • CPR (counts per revolution) - The number of quadrature state changes per revolution, or PPR x 4
  • Detents - These prevent unwanted rotation and provide a “click” every time the shaft is rotated a certain number of degrees
  • Push Switch - The encoder shaft can be pressed down to actuate a simple SPST switch

Pulses


CUI's rotary encoders output a square wave signal. The signal is comprised of a series of pulses, which are defined as one full square wave cycle, or a transition from low to high back to low, or high to low back to high. Simply stated, a pulse is a measure of the waveform from one identical point to the next.

Output


CUI's rotary encoders utilize square waves with two channels that are offset 90 electrical degrees from each other. By detecting which channel is leading the other, direction can be monitored.

  • Square wave output over two channels
  • The signals are identical except they are slightly offset
  • By detecting which signal is leading, the direction of rotation can be monitored

Most applications will use quadrature state changes to increase the counts per revolution. Increasing the counts per revolution increases the effective resolution of the encoder. In this case, one cycle is a transition from low to high back to low on both channels.


Microcontrollers use different methods for counting:

  • Pulses on one channel - 1 count per pulse
  • Pulses on two channels - Using both channels doubles the number of counts
  • Quadrature state changes - 4 counts per cycle

Sinking and Sourcing

Most panel mount encoders need to be connected to a microcontroller that can source current. The microcontroller provides a path to V+ and the encoder provides a path to ground creating a complete circuit. Another term commonly used for sinks is “open collector.” This means the collector of the output transistor is external to the unit.

  • Sinks provide paths to ground
  • Sources provide paths to a voltage
  • A sink needs a source to work and vice versa. A faucet needs a sink, and a sink needs a faucet
  • CUI Inc panel mount encoders sink current, requiring a source to work properly

Mechanical vs. Optical Technology

Mechanical encoders are less expensive and can handle a wider range of voltages. However, they require de-bounce circuitry to produce a clean signal and have a shorter life cycle. Optical encoders, on the other hand, are typically more expensive but have a higher life cycle and provide a cleaner output signal that does not require de-bounce circuitry. Additionally, for precision applications, optical encoders can provide higher resolutions.

Mechanical

  • Inexpensive
  • Rugged
  • Variable source coltage levels

Optical

  • Cleaner output
  • Longer lasting
  • Less external circuitry
  • Higher resolution

How Optical Encoders Work


Optical encoders are made up of three basic parts: a light source, a light detector, and a code wheel. The source shines light through slits in the code wheel and the detector senses this light. The code wheel has evenly spaced slits which transmit and alternately block the light source. Internal circuitry enables and disables an output depending on whether or not the light is being detected or blocked.

  • Attached to the shaft, inside the encoder body is a wheel a with slits cut in at regular intervals
  • A beam of light is aimed across the code wheel
  • A detector on the other side is used to tell if the beam is being transmitted through a slit or blocked by the material between slits
  • As the shaft is turned, the light beam is alternately blocked (state=0) or transmitted (state=1)

How Mechanical Encoders Work


Mechanical encoders are essentially a series of switches. The code wheel contains contacts spaced evenly along its outer edge. Another contact is stationary and mounted on the encoder chassis. As the code wheel turns it makes, then breaks, contact with the code wheel contacts, one at a time.  This making and breaking of a circuit generates a voltage pulse which can be read by a microcontroller.

  • A code wheel with contacts turns inside the unit as the encoder shaft is turned
  • When contact is made the voltage at the output is pulled up
  • When contact is broken the output is pulled low

Switch Bounce and Debounce


In a perfect world, a switch is characterized by having two states, on and off. Unfortunately, in the real world, switches can hover or bounce between the two states, creating a distorted signal. Switch bounce can be incorrectly read as additional pulses by a microcontroller. To prevent this debounce, circuitry is used to “square up” the output. Because mechanical encoders are essentially a series of mechanical switches, they require debounce circuitry and programming to ensure that the output can be used.

  • An ideal switch will have two states, on and off, and it will instantly move to one of these positions
  • In the real world a switch will hover, or bounce, between these states during switching operations
  • To compensate for this effect, switches need “debounce” circuitry and/or programming

Available Products
C14 Optical Encoder Series


The C14 optical encoder series holds some advantages when compared to other optical encoders on the market. It is compact, measuring 15 mm across. The body and shaft feature metal construction, creating a rugged package that can be further protected with the optional IP65 rating. The C14 outputs a crisp, clean square wave, making interpolation easier and more accurate for the microprocessor. Finally, with a rotational and push button life of 1 million cycles, the C14 is built to last.

The series is available in 30 configurations. Some of the key options include 16 and 32 pulses per revolution, configurations with and without push button, with and without detent, multiple shaft styles, and three different mounting orientations.

C14 Optical Encoder Options

  • 16 & 32 PPR (64 & 128 CPR)
  • Push switch or no switch
  • Detents or no detents
  • 6 different termination types
  • 3.175, 6, 6.35 mm shaft diameter
  • 5 different mounting types
  • Optional IP65 rating

Product Benefits

  • Compact – 15 mm width
  • Rugged – Metal body construction and optional IP65 rating
  • Quadrature output
  • Clean square wave output
  • Life – 1,000,000 cycles

ACZ Mechanical Encoder Series


The ACZ mechanical encoder series is available in 40+ configurations. Some of the key options include various resolutions, configurations with and without push button, with and without detent, multiple shaft styles, and two different PCB mounting orientations.

C14 Optical Encoder Options

  • 12, 15, 20 ,30 PPR
  • Push switch or no switch
  • Detents or no detents
  • 15, 20, 25 mm shaft length
  • Horizontal or vertical mounting

Summary

CUI's ACZ and C14 Encoder series are designed to provide an accurate and inexpensive method for user input across a wide range of applications. The ACZ series utilizes mechanical encoder technology, offering a rugged, low cost solution. The C14 series on the other hand utilizes optical encoder technology, offering a clean signal and long life cycle for high precision applications. Overall, CUI's wide range of options and features provides a reliable solution for virtually any customer need. For more information, please see our website.


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