06/12/2016
ENCODER – SOLVING AUTOMATION SHOP FLOOR APPLICATIONS IS OUR PRIMARY COMMITMENT
M.D. Micro Detectors, leader in design, development and manufacture of photoelectric, ultrasonic, inductive, capacitive and area sensors as well as safety products. In order to be recognized as a complete product supplier for all the typical industrial automation shop floor applications offering a more complete range is glad to introduce a NEW OPTICAL INCREMENTAL ENCODER SERIES.

Working principle

An encoder is a rotary transducer that converts an angular movement into a series of electrical digital pulses. If associated to racks or endless screws, these generated pulses can be used to control angular or linear movements. During rotation, electrical signals can be elaborated by nu¬merical controls (CNC), programmable logic controls (PLC), control systems, etc. Main applica¬tions of these transducers are: machinery, robots, motor feedback, measurement and control devices.

The encoder is formed by: :
  • Mechanical interface
  • Code wheel (or magnetic actuator or linear scale)
  • Optoelectronic receiver or magnetic sensors
  • Electronic interface


Encoders use two main technologies to detect the signals: :
  • Photoelectrical or optical scanning
  • Magnetic field variation


In M.D. Micro Detectors encoders, the angular movement transduction is based on the photo¬electric scanning principle. The reading system is based on the rotation of a radial graduated disk formed by opaque windows and transparent ones alternated. The system is perpendicularly illuminated by an infrared light source.

The light projects the disk image on the receiver’s surface which is covered by a grating called a collimator having the same disk steps. The receivers transduce the occurring light variations caused by the disk shifting and convert them into their corresponding electrical variations. Electrical signals, raised to generate squared pulses without any interference, must be electronically processed. The reading system is always carried out in differential modality, that is comparing different signals nearly identical but out of phase of 180 electrical degrees. That in order to increase quality and stability of output signals. The reading is performed by comparing the difference between the two channels, to remove the noise known as “common mode”, because signals are overlapped in equal way on each wave.

Incremental encoder

The incremental encoder usually gives two types of squared waves out of phase of 90 electrical degrees. They are usually called channel A and B. The first channel gives information about the rotation speed while the second, basing on the state sequence produced by the two signals, provides the direction of rotation. A further signal, called Z or zero channel, is also available. It gives the absolute zero position of the encoder shaft. This signal is a squared pulse with phase and width centered on A channel.

The incremental encoder accuracy depends on mechanical and electrical factors. These errors could be: grating division, disk eccentricity, bearings eccentricity, electronic reading and optical inaccuracy. The measurement unit to define encoder accuracy is the electrical degree. It deter¬minates the division of the impulse generated by the encoder: 360 electrical degrees correspond to the mechanical rotation of the shaft which is necessary to carry out a complete cycle. To know how many mechanical degrees correspond to 360 electrical degrees the following formula has to be applied:
Elettrical 360° = (Mechanical 360° )/((n° pulses)⁄turn)
The encoder division error is given from the maximum shifting shown in the electrical degrees of two consecutive edges. This error exists in any encoder and is due to the above mentioned factors. On M.D. Micro Detectors encoders pulse error is ±18° and max. on full operating range, which corresponds to a ±10% from nominal value. Regarding the 90 electrical degrees phase relation between the two channels, it differs in ±35 electrical degrees max which corresponds to ±10% respect to signal period.

Mechanical Interface

The mechanical interface consists in all those components that allow the coupling of the encoder to the machine or device of application, which are:
  1. An axle, connected to the shaft of the machine in rotation, designed in accordance to the type of fixing: solid shaft, blind and through hollow shaft;
  2. A flange, which fixes and adjusts the encoder to its support;
  3. A case (or body), which contains and protects the disc and the electronic components.
Elastic couplings can also be employed to adapt the fixing between the motor shaft and the encoder.

Electronic Interface

The electronic interface consists in all the input and output components that allow both the power supply and the transmission of electric pulses of the encoder.

In the incremental system, the transmission of output signals occurs through one or more channels and could be of different kinds:
  • NPN and NPN open collector
  • PNP and PNP open collector
  • Push-Pull
  • Line driver
In the absolute system, the transmission of output signals could be parallel, serial (SSI), or of field-bus type (Profibus DP communication protocol for example).

Incremental Encoder Electronic Interface

NPN and NPN open collector

This type of electronic output is composed by a NPN transistor and a pull-up resistor used to match the output voltage to the power supply when the transistor is off. It has low saturation levels at 0Vdc and close to 0 at the positive. It is proportionally influenced by the cable length, pulses frequency and by the load, so these factors should be considered to meet the application’s needs.
The open collector variant differs since it has no pull-up resistor, therefore the collector of the transistor is free from the constraint of the encoder power supply, allowing to obtain signals with different voltage.

PNP and PNP open collector

Main characteristics and limitations of the PNP interface are the same as for NPN electronics. The main difference lies in the transistor, which is a PNP type. The resistor, if present, is a pull-down one. Therefore, it is connected between the output and 0V.

Push-pull

In NPN or PNP electronics the major limitations are caused by the resistor, which works with a much higher impedance than a transistor. To overcome this issue, the Push-Pull circuit uses a complementary transistor, so the impedance is lower for commutation to positive and to zero. This solution increases frequency performances allowing longer cable connections and an optimal data transmission even at high working speed. Saturation signals are low, though higher than in NPN and PNP electronics. It is anyhow possible to apply indifferently the Push-Pull electronics also to NPN or PNP receivers, which is also TTL compatible (5Vdc power supply).

Line-driver

The Line-Driver output is employed when operating environments are particularly exposed to electrical interferences or when the encoder is quite far from the receiver system. Data transmission and reception work on two complementary channels, so the noise caused by the cross-talk from other cables is reduced. In Line-Driver instead, signals are transmitted and received in «differential» way; in other words, the communication works based on the difference of voltage between complementary channels. This type of transmission is used in 5Vdc systems and is compatible also with RS422; it’s also available with power supplies up to 24Vdc for harsh environments applications.

Output stage protection

A highly integrated driver is used to protect outputs from short circuits. This solution is based on an active sensor which controls instantly the temperature reached by the element to be protected. In this way, protection is very effective. Moreover, it ensures a constant protection against repetitive and permanent short circuits, which is why it is strongly suggested for heavy duty applications. It’s available for Line-Driver and Push-Pull electronics.

M.D. MICRO DETECTORS ENCODER OFFER The new MDI series is DIRECT REFLECTION optical working principle based. Differently from classical TRANSMISSION based, these ones are definitely better in respect of transmission frequency, resolution, reliability, robustness, response time, temperature stability and much more compact. M.D. Micro Detectors offer is made by three SOLID SHAFT incremental encoder families:
  • MDI40A
  • MDI58B/C
  • MDI63A/D
Together with three HOLLOW SHAFT incremental encoder families:
  • MDI38F/G
  • MDI58F/G
  • MDI63F/G
Each product line is provided with several different models, depending on resolution, flange type, flange dimension, electronic output logic and output type.

MDI40A Series

MDI40A series is made by solid shaft models, 42mm dimension with Flange Type A with 6mm shaft dimension. Models with and without ZERO PULSE are available together with models Push-Pull or Line Driver output logic. Standard mechanical protection is IP54 but models with IP66 protection are available equipped with special bearings All MDI40A are with standard 0.5m radial cable exit. Longer cable models are available on demand.

MDI58B/C Series

MDI58B/C series is made by solid shaft models, 58mm dimension with Flange Type B and Type C with 6mm and 10mm shaft dimension. Models with and without ZERO PULSE are available together with models Push-Pull or Line Driver output logic. Standard mechanical protection is IP54 but models with IP66 protection are available equipped with special bearings MDI58B/C series provides: Standard 1.5 m radial cable exit versions. Longer cable models are available on demand. 7-poles Type M Amphenol MS3102-E-16-S (for Push-Pull models) or 10-polse M Amphenol MS3102-E-18-1 (for Line Driver models) RADIAL or AXIAL MILITARY (MIL) Connector. 5-poles (for Push-Pull models) or 8-poles (for Line Driver models) RADIAL or AXIAL standard M12 connector;

MDI63A/D Series

MDI63A/D series is made by solid shaft models, 63mm dimension with Flange Type A and Type D with 9mm and 10mm shaft dimension. Models with and without ZERO PULSE are available together with models Push-Pull or Line Driver output logic. Standard mechanical protection is IP54 but models with IP66 protection are available equipped with special bearings MDI63A/D series provides: Standard 1.5m radial cable exit versions. Longer cable models are available on demand. 7-poles Type M Amphenol MS3102-E-16-S (for Push-Pull models) or 10-polse M Amphenol MS3102-E-18-1 (for Line Driver models) RADIAL or AXIAL MILITARY (MIL) Connector. 5-poles (for Push-Pull models) or 8-poles (for Line Driver models) RADIAL or AXIAL standard M12 connector;

MDI38F/G Series

MDI38F/G series is made by hollow shaft models, 38mm dimension with Flange Type F and Type G with 6mm, 8mm and 10mm hole dimension. Models with and without ZERO PULSE are available together with models Push-Pull or Line Driver output logic. Standard mechanical protection is IP54 but models with IP66 protection are available equipped with special bearings MDI38F/G series provides: Standard 0.5m radial cable exit versions. Longer cable models are available on demand. 7-poles Type M Amphenol MS3102-E-16-S (for Push-Pull models) or 10-polse M Amphenol MS3102-E-18-1 (for Line Driver models) RADIAL MILITARY (MIL) PIG-TAIL Connector are available ON DEMAND. 5-poles (for Push-Pull models) or 8-poles (for Line Driver models) RADIAL standard M12 connector are available ON DEMAND;

MDI58F/G Series

MDI58F/G series is made by hollow shaft models, 58mm dimension with Flange Type F and Type G with 6mm and 10mm hole dimension. Models with and without ZERO PULSE are available together with models Push-Pull or Line Driver output logic. Standard mechanical protection is IP54 but models with IP66 protection are available equipped with special bearings

MDI58F/G series provides: Standard 1.5m radial cable exit versions. Longer cable models are available on demand. 7-poles Type M Amphenol MS3102-E-16-S (for Push-Pull models) or 10-polse M Amphenol MS3102-E-18-1 (for Line Driver models) RADIAL or AXIAL MILITARY (MIL) Connector. 5-poles (for Push-Pull models) or 8-poles (for Line Driver models) RADIAL or AXIAL standard M12 connector;

MDI63F/G Series

MDI63F/G series is made by hollow shaft models, 63mm dimension with Flange Type F and Type G with 6mm and 10mm hole dimension. Models with and without ZERO PULSE are available together with models Push-Pull or Line Driver output logic. Standard mechanical protection is IP54 but models with IP66 protection are available equipped with special bearings MDI63F/G series provides: Standard 1.5m radial cable exit versions. Longer cable models are available on demand. 7-poles Type M Amphenol MS3102-E-16-S (for Push-Pull models) or 10-polse M Amphenol MS3102-E-18-1 (for Line Driver models) RADIAL or AXIAL MILITARY (MIL) Connector. 5-poles (for Push-Pull models) or 8-poles (for Line Driver models) RADIAL or AXIAL standard M12 connector; Ease of Use, great functional flexibility but mostly wide and complete applicative coverage are distinctive characteristics of this new Encoder family.

Main Features



MECHANICS:

  • Solid and Hollow Shaft
  • A,B,C,D,F,G Flange Type
  • 6,8,9,10 mm Shaft or Hole Dimension
  • IP54 or IP66 mechanical protection
  • Plastic or Metal housing

    ELECTRONICS:

  • Line Driver (differential) TTL or Push Pull HTL output logic
  • 5/30Vdc Power Supply
  • With or Without ZERO PULSE

    RESOLUTION:

  • From 100 up to 2500 pulse per revolution

    Applications/sectors

  • Logistic/material handling
  • Automatic warehouse
  • Woodworking Machinery
  • Robotics
  • Packaging
  • Engines
  • Agricultural vehicles
  • Elevators and lifts
  • Biomedical

    Special and Custom models

    The encoder application scenario is extensive and detailed. In order to meet customer requirements, we are often faced with the need to provide the product with particular mechanical, fixing holes of size and positions related to the mechanics of the machine itself and also the flange and the shaft may vary in size, shape and features. In addition, the electronics, the connectivity and even the pin-out of the electrical signals can be customized in order to minimize the impact of encoder installation. M.D. Micro Detectors, thanks to its flexibility and ability to create customized and personalized versions based on the demands and needs of its customers, even on the encoder family is able to provide special versions that match the best mechanical and electrical characteristics of the machine.

    By combining expertise in the various technologies (proximity, photoelectric, ultrasonic, area and safety sensors and now Encoder) M.D. Micro Detectors is recognized as sole supplier for the sensors to be used on your machines. This is not only due to the high quality and technology expressed in our products but also due to aspects like flexibility, speed, quality and above all excellent levels of service, features that cannot be ignored in the complex and demanding market of industrial automation.
  • Back to news