1. Encoders and Resolvers Series:
Motion Feedback 101
Select the Right Feedback for Your Application by Knowing the Basics

2.  This webinar will be available afterwards at
designworldonline.com & email
 Q&A at the end of the presentation
 Hashtag for this webinar: #DWwebinar
Before We Start

3. Moderator
Miles Budimir
Design World
Presenter
Mark Langille
Technology Planner, Dynapar Corp.

4. Mark Langille is the Technology Planner for Dynapar. He has worked in the
encoder industry for 15years both on the manufacturing and commercial side of
the business, with 7 years spent as a manufacturing engineer. He holds a BS in
Industrial Technology with an emphasis in manufacturing from Iowa State
University.

5. Closed-loop feedback can deliver:
 Speed data—spindle applications,
CNC tools, conveyor belts
 Velocity data—web applications
 Position data—packaging, pick-and-place
You can close the loop on:
 Shaft velocity/position provided from an
encoder or resolver
 The motor torque via motor current
 The load—high-performance apps
o removes lost motion, hysteresis
Knowledge is Power
position velocity

6.  Resolution (optical versus magnetic)
 Accuracy (optical or magnetic subtype)
 Velocity ripple- Symmetry specification
 Uptime/reliability (incremental
versus absolute)
 Cost of material/time during reset
(incremental versus absolute)
 Mechanical constraints—shaft type, speed
 Environmental constraints (IP ratings)
How to Choose…

7. Different Horses for Different Courses
Encoders vs. Resolvers

8.  Special type of rotary
transformer
o Stationary stator, rotor moves
with the load
o Voltage from input winding
couples to output winding
o Ratio of voltages gives
angular position
Resolvers
Single Speed Resolver Output
-1
-0.5
0
0.5
1
0 45 90 135 180 225 270 315 360 405
Degrees
Amplitude
Sine
Mod Sine
Cosine

9. 155ºC Rated Winding
(Optional 220ºC) for High
Temp Environments
Flux Shield Eliminates
Crosstalk (pat. pend.)
Precision Laminations
Help Assure High Accuracy
No On-Board
Electronics Means
Resolvers Can Be
Used Where
Encoders Cannot. Multi-Pole Versions in
Both Housed and
Frameless Models to
Size 55 Available
Housed Version

10.  High res--no onboard electronics, very rugged
o Temperature extremes
o Elevated radiation levels—no SEUs
o Contamination
o Shock and vibration
 Analog—infinite resolution
 Good for tough applications like aerospace,
servo, and CNC.
But…
 The electronics have to go somewhere
 Skill required for integration
Resolver Trade-Offs

11.  Linear or rotary feedback
 Moving load/motor modulates signal
 Output driver converts signal to
speed/velocity/position
Encoders

12.  Complete – All digital electronic output
 Robust
o Potted electronics
o Many design utilize ASIC’s
 Lots of options
o Optical vs. magnetic
o Incremental vs. absolute
o IP rated
o Multiple mounting styles
But…
 Know your design criteria both electrical/mechanical.
Selecting the right device for specific for the
applications can make the difference.
Encoder Tradeoffs

13. Poll Question #1
In rugged environments it is best to specify:
a) Resolvers
b) Magnetic encoders
c) Optical encoders
d) Depends on the application

14. Optical vs. Magnetic

15.  Disk—mounted on load or motor shaft
o Glass substrate patterned with metal thin film
o Mylar substrate (speed limitations--flutter)
 Sensor—mounted on housing
o LED to generate beam
o Photodiode to detect beam
o Board level or chip level integration
 Turning/moving disk modulates beam
 Device uses this info to derive velocity/position
feedback
Optical Encoders

16.  Mask (multichannel encoders only)
o Prevent spillover between channels
o Or introduces phase shift between channels
 Phased-array encoder—onboard ASIC
o Array of detectors averages signal
o Compensates for misalignment
o More robust—shock loads up to 400 g
o Easier to integrate—no need for potentiometers
o Larger air gap [give amount– millimeters?]
o Batch processing keeps price down
Best for:
 Medical, semiconductor, elevators, oil and gas,
aerospace, heavy vehicles
Optical Encoders

17.  High resolution (up to 10,000 PPR incremental
direct read or 1×106 PPR for absolute versions
(more on that later).
 Ease of installation
 EMI immune
 Shock resistant
 Lower-cost
But…
 IP (ingress protection) is important
 Most optical encoders utilize bearings and
LED which can have a finite life.
Optical Encoder Trade-Offs

18.  Drum/strip with alternating magnetic—
mounted to shaft/load
 Readout electronics—mounted on housing
 Output based on responses system to
perturbed magnetic field
Best for:
 Mill applications, cranes, extruders, wash-down
environments
Magnetic Encoders

19.  Variable reluctance
o Magnetic pickup—permanent
magnet wound with coil
o Changing magnetic field
generates voltage pulse
o Pro: simple; con: limited to 240 PPR
 Magnetoresistive
o Resistor array changes resistance
when drum turns
o Pro: better resolution, lithographically
patterned
o Cons: larger, not actually integrated,
needs support circuitry
Magnetic Encoders

20. Hall-effect sensor arrays:
 Solid-state detector – applied
magnetic field separates charge carriers
 Separation triggers voltage spike
 Process to get speed/displacement
Pros:
 Sensor and processor on same chip
 Integrated – robust, compact, economical
 Data averaged over multiple detectors – lower noise, higher
sensitivity
Magnetic Encoders

21.  Tough—unaffected by
o contamination
o Temperature extremes
o Shock/vibration
o Stable performance – no degradation
But…
 Lower resolution than optical encoders
 Can be affected by high magnetic fields
Magnetic Encoder

22. Which type of rotary feedback typically can provide the
highest accuracy resolver, optical encoder,
or magnetic encoder?
a) Resolver
b) Optical encoder
c) Magnetic encoder
d) Depends more on the
more on the application/environment
Poll Question #2

23. Incremental vs. Absolute

24.  Can measure speed, velocity, and
direction, depending
 Track counts traveled from
some home position
 Generate pulse stream only—
need PLCs, drives, etc. to
convert to info
Incremental Encoders

25.  2+ channels, 90° out of phase (in quadrature)
 One channel goes high first—directionally
dependent
 More channels equals more resolution
 Triggering (leading edge, trailing edge) ups
resolution
 Index channel monitors turns
Best for:
 Web apps, e.g. printing, paper
 Packaging equipment
 Motor/Drive application with tight PID
speed loops
Quadrature Encoders

26.  Up to 32768 PPR with interpolation
 Simple to integrate
 Easy to maintain
 Variety of form factors and prices
But…
 Need to be re-homed on start up
 Can require 10 conductor cables
Incremental Encoder
Trade-Offs

27.  Output as a digital word corresponding to absolute position
 Code disc -- each ring corresponds to one bit of resolution
 Each ring read by separate LED/detector pair
 Standard resolution--12 bits (4096 PPR)
o As high as 22 bits (4.19 x 106 positions)
 Multi-turn designs to track multiple turns of shaft (to 4096)
 Support many bus/Ethernet based communication protocols
Best for:
 Hi-accuracy applications: Medical, aerospace, semiconductor
 Multi Axis machines with coordinated motion
 Serial versions are best for ultra low speed PID loop
Absolute Encoders

28.  No need to re-home on start-up
 Faster start up time
 Greater accuracy
 Bus compatible
 Deliver real-time diagnostics
But…
 Tend to be more expensive
 More complex to install
Absolute Trade-Offs

29. Poll Question #3
Which device allows you sense the
absolute shaft position with in one rotation
a) Optical – Incremental with index
b) Optical - Absolute
c) Magnetic
d) Resolver
e) All of the above

30. Mounting Types

31.  Coupled to:
o non-loadbearing end of motor shaft
o gear box/measuring wheel.
 Robust
 Greatest variety of options
Tip: Connect to rotating shafts via belts, wheels, or flexible coupler.
Be mindful that the dynamic loads don’t exceed the encoders’
bearings rating.
Shafted Encoders

32.  Fits over motor shaft with a
pressure connection
 Automatic alignment
 No need for couplers
 Rapid installation
But…
 Tether mounting shouldn’t be
shouldn’t be taken for granted
Best for: AC Induction Motor
Feedback
Hollow-Shaft Encoders

33.  Sensor unit on the motor shaft
 Housing connected to the motor housing
 No bearing—less maintenance, fewer
failures, smaller, lighter
 Non-contact sensing
Application tip: Play close attention to shaft
run out and end play under mechanically
loaded conditions.
Bearingless Encoders

34. IP Ratings

35.  IEC 60529 --protection against solid and liquid
 Two digit system
o first digit, solids----fingers to dust
o second digit, liquids----droplets to high-pressure Jets
 IP ratings specify time durations, depth, etc. , so pay
attention
 No one seal can do both----identify your priorities
Know the Code

36. Know the Code
IP 67 – 6 7
Pay attention to Time limits, Pressure limits, Depth limits, Angle dependence.
Solids

37. Putting It
All Together

38.  Performance requirements
o Accuracy
o Resolution
o Symmetry/Phase
o Electrical interface
 Environmental conditions
o Temperature
o IP Rating
o Shock/vibration
o Overall reliability
 Budget
o TCA versus TCO
Know your application…

39.  Choose a resolver for the very harshest applications.
 Choose optical encoder when you need the best resolution possible.
 Choose a magnetic encoder when you need the best of both worlds.
 A high IP rating can’t compensate for the wrong choice of encoder
type.
 No one feedback device can do it all – decide what’s most
important and design to it.
In Summary

40. Questions?
Design World
Miles Budimir
mbudimir@wtwhmedia.com
Phone: 216.860.5271
Twitter: @DW_RapidMfg
Dynapar
Mark Langille
mark.langille@dynapar.com
Phone: 847.782.5211
Twitter: @encoders

41. Thank You
 This webinar will be available at designworldonline.com & email
 Tweet with hashtag #DWwebinar
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