E8P OEM Optical Kit Encoder

E8P Features

  • Subminiature size, easy installation
  • Single-ended or differential output option
  • A and B quadrature TTL outputs
  • Fits shaft diameters from 0.118 in. (3mm) to 0.276 in. (7mm)
  • Accepts +/- 0.020 in. axial shaft play
  • Off-axis mounting tolerance of 0.010 in.
  • Count frequency from DC to 30 kHz
  • 180 to 512 cycles per rev (CPR)
  • 720 to 2,048 quadrature states per rev.
  • Single +5V supply

See more info below

Configure the E8P

The E8P has reached its End of Life (EOL) and is no longer available for purchase. See E8T for replacement product information.

The E8P is no longer available for purchase.

E8P Product Description

Restriction of Hazardous Substances

The E8P optical incremental kit encoder is designed for high volume, low cost, mid-resolution OEM motion control applications. The E8P is small enough for a NEMA Size 11 stepper motor.The E8P uses a single 5V supply and offers two TTL quadrature outputs. Single-ended or differential output options are available. A single chip reflective encoder module incorporates an LED, monolithic detector and molded lenses. The phased array technology accepts far wider mechanical tolerance and misalignment than traditional aperture type encoders. The E8P uses an innovative, patent pending, push-on encoder disk that provides extremely secure and accurate, yet easy installation without setscrews.  

The E8P provides mounting holes for two #4-40, length .250" screws or two M2.5x.45mm, length 6mm screws on a 0.75" diameter bolt circle. When mounting holes are not available, an  option with a transfer adhesive pre-applied to the base is available. A centering tool is provided to center the base to the motor shaft during installation. The encoder disk pushes on by hand using a spacer tool to set the gap in one step. The cover snaps on to complete the assembly in seconds.

The single-ended output version has a 4-pin high retention polarized connector and is designed to drive cables up to six feet long. For longer cable lengths, the differential output version (6-pin connector) is recommended to maximize noise immunity. The internal 26C31 differential line driver can source and sink 20 mA at TTL levels. The recommended receiver is industry standard 26C32. Maximum noise immunity is achieved when the differential receiver is terminated with a 150 Ω resistor in series with a .0047 μF capacitor placed across each differential pair. The capacitor simply conserves power. Otherwise power consumption would increase by approximately 20 mA per pair, or 40 mA for 2 pairs.

Product Specifications

View here or download the specifications


Vibration (5Hz to 2kHz) 20 G
Max. Relative Humidity 90 %
Storage Temperature -40 to 100 C
Operating Temperature -20 to 100 C
Electrostatic Discharge, IEC 61000-4-2
Single-ended (S-option)
Differential (D-option)

± 8
± 2



Moment of Inertia 1.81 x 10-5  oz-in-s2
Required Shaft Length
  With D-Cover option
  With H-Cover option

0.385" to 0.400"

Mounting Screw Torque (-D, -M option) 2-3 in.-lbs
Shaft Axial Play ± .020 in.
Off-axis Mounting Tolerance ± .010 in.
Acceleration 250000 max. rad/sec²
Maximum RPM (1)
e.x. CPR = 720, max. rpm = 5000
e.x. CPR = 180, max. rpm = 20000
minimum value of
and (60000)
Technical Bulletin TB1001 - Shaft and Bore Tolerances Download

(1) 60000 rpm is the maximum rpm due to mechanical considerations. The maximum rpm due to the module's 30kHz maximum count frequency is (3600000/CPR).

Base Options

Base OptionBolt CircleScrews Included
D 0.75" #4-40, length .250" pan head phillips (qty: 2)
M 0.75" M2.5x.45mm, length 6mm pan head phillips (qty: 2)
T n/a none - .005" thick transfer adhesive with peel away backing mount.

The included centering tool and spacer tool are used to center the base to the motor shaft and to set the codewheel gap.

Single-ended Electrical

Supply Voltage 4.5 5.0 5.5 V  
Supply Current   21 27 mA no load 
Low-level Output     0.4 V IOL = 6 mA
High-level Output 2.4     V IOH = -1 mA
Rise Time   500   ns CL = 25 pF, RL = 2.7 kΩ
Fall Time   100   ns  

Differential Electrical

Supply Voltage 4.5 5.0 5.5 V  
Supply Current   23 30 mA
Low-level Output   0.2 0.4 V IOL = 20mA max.
High-level Output 2.4 3.4   V IOH = -20mA max.
Differential Output Rise/Fall Time     15 ns

Phase Relationship


Symmetry, S 180 ± 16 180 ± 75 electrical degrees
Quadrature Delay, Q 90 ± 10 90 ± 60 electrical degrees

(1) A leads B for clockwise shaft rotation, and B leads A for counterclockwise rotation viewed from the cover/label side of the encoder.

(2) Typical values represent the encoder performance at typical mounting alignment, whereas the maximum values represent the encoder performance across the range of recommended mounting tolerance.


4-pin Single-ended (1)6-pin Differential (2)
1 +5VDC power 1 Ground
2 A channel 2 A channel
3 Ground 3 A- channel
4 B channel 4 +5VDC power
    5 B channel
    6 B- channel

(1) 4-pin single-ended mating connector is CON-MIC4
(2) 6-pin differential mating connector is CON-MIC6

Assembly Instructions

1. PCB Installation

Position the PCB so that connector lines up with flat side of base. Push PCB onto base by hand so that the two guide posts fit into associated PCB holes.

2. Base Installation

2a. Standard: Secure base to mounting
surface with provided mounting screws.

2b. Transfer Adhesive: Slip centering tool over shaft and into center hole of base. Slide both parts down shaft until they contact mounting surface. Press base firmly to assure good adhesion. Remove centering tool.
3. Codewheel Installation

Set codewheel on shaft with disk facing base. Place spacer tool over codewheel with recess areas over connector and base tabs. Push tool down by hand until it bottoms out against base. Remove reusable spacer tool. In order to prevent permanent damage to motor bearings (especially on small diameter shaft motors), it is recommended that the far end (drive end) of the motor shaft be supported while installing the push on hub.

4. Cover Installation

Snap cover onto base.


1. Centering Tool

The centering tool is only included with the -3 packaging option. It has to be ordered separately for other packaging options.

Part #: CTOOL - (Shaft Diameter)
Description: This reusable tool provides a simple method for accurately centering the E7P base to the shaft. A centering tool is highly recommended when using the T-option transfer adhesive.

2. Spacer Tool

A spacer tool is included for all packaging options.

Part #: SPACER-E8P
Description: This reusable tool is used to properly space the codewheel from the encoder.

Product Change Notification

Title Date Description Download
EOL - E7P - E8P - PCN 5894 02/08/2017 As part of our on-going product lifecycle management process, we have identified products that will be transitioned to an "End-of-Life" status. Products targeted for end-of-life may be available for a last time buy option prior to being made obsolete, however quantities are limited and special requirements may apply.  Download

Additional Information

Product Notes

  • Cables and connectors are not included and must be ordered separately.
  • US Digital® warrants its products against defects in materials and workmanship for two years. See complete warranty for details.

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