AS37-H39B-K21S Optical Rotary Encoder - Equivalent & Substitute Parts

Part Overview

The AS37-H39B-K21S is an optical rotary encoder manufactured by Broadcom Limited, classified as a sensor/transducer component. This encoder operates as a binary absolute output device with a vertical chassis-mount orientation and connector-based termination. The product is currently obsolete, making identification of functionally equivalent substitute components essential for system maintenance, redesign, and procurement planning.

Substiute Parts

AS37-H39B-K21S

Broadcom LimitedIn Stock: 1153AS37-H39B-K21S Datasheet

Current PartRFQ

AS33-M42M-K53

Broadcom LimitedIn Stock: 1054AS33-M42M-K53 Datasheet

MFR RecommendedRFQ

AS33-M42M-K54

Broadcom LimitedIn Stock: 905AS33-M42M-K54 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the AS37-H39B-K21S requires evaluation of the following critical parameters that define functional equivalence:

Voltage Supply Compatibility: Both substitute parts operate within the identical 4.5V ~ 5.5V supply range, ensuring direct electrical compatibility.

Mounting and Orientation: Both substitutes maintain chassis mount configuration with vertical orientation, preserving mechanical fit within existing enclosures.

Termination Interface: Connector-based termination is retained across all substitute options, allowing direct integration with existing harnesses and connectors.

Compliance Standards: All substitute parts maintain ROHS3 compliance and identical ECCN/HTSUS classifications, satisfying regulatory and procurement requirements.

Key Difference - Encoder Technology: The substitute parts transition from optical encoding (AS37-H39B-K21S) to magnetic encoding (AS33-M42M series). This represents a functional technology shift while maintaining absolute position output capability through programmable pulse resolution.

Key Difference - Output Protocol: The substitutes employ RS-485 serial communication instead of binary output, requiring interface adaptation in signal processing circuits.

Parameter Comparison

Engineering Selection Recommendations

Product Status Consideration: The AS37-H39B-K21S is classified as obsolete, necessitating transition to active production parts. Both AS33-M42M-K53 and AS33-M42M-K54 maintain active product status with confirmed inventory availability, ensuring long-term supply chain viability.

Compliance and Certification: All three parts maintain identical ROHS3 compliance status and matching ECCN/HTSUS classifications (EAR99 / 8543.70.4500), satisfying regulatory requirements without modification to procurement or export documentation.

Voltage Supply Alignment: The 4.5V ~ 5.5V supply range is preserved across all options, eliminating power supply redesign requirements.

Mechanical Integration: Vertical chassis mount orientation with connector termination is maintained, supporting direct mechanical substitution within existing enclosure designs.

Functional Transition: Selection between AS33-M42M-K53 and AS33-M42M-K54 depends on actuator hub size requirements (M3 versus M4), with both providing magnetic encoding and RS-485 output as active alternatives to the obsolete optical binary encoder.

Frequently Asked Questions (FAQ)

Q: Why are the substitute parts magnetic encoders instead of optical? A: The AS37-H39B-K21S is obsolete. Broadcom Limited's active product line for rotary encoders in this form factor and voltage class has transitioned to magnetic encoding technology. The AS33-M42M series provides functionally equivalent absolute position sensing with programmable resolution and active product support.

Q: What is the difference between AS33-M42M-K53 and AS33-M42M-K54? A: Both parts are identical except for actuator hub size. The K53 variant features an M3 hub, while the K54 variant features an M4 hub. Selection depends on the shaft diameter of the driven component. Both require an external magnet (not included) for operation.

Q: Can I use these substitutes as direct drop-in replacements? A: Mechanical fit is compatible (vertical chassis mount, connector termination). However, the output protocol changes from binary to RS-485 serial communication, requiring signal processing circuit modification. The external magnet requirement for magnetic encoders also differs from the shaft-hole design of the optical encoder.

Q: Are the supply voltage requirements identical? A: Yes. All three parts operate within the 4.5V ~ 5.5V range, eliminating power supply redesign.

Q: Do the substitute parts maintain RoHS compliance? A: Yes. Both AS33-M42M-K53 and AS33-M42M-K54 are ROHS3 compliant with identical ECCN and HTSUS classifications to the original part.

Q: What does "Pulses per Revolution - Programmable" mean for the substitutes? A: The AS33-M42M series allows configuration of output resolution through programming, providing flexibility in absolute position sensing granularity. The original AS37-H39B-K21S does not specify this parameter.

Q: Are these parts available in stock? A: Yes. AS33-M42M-K53 has 1043 pieces in stock, and AS33-M42M-K54 has 818 pieces in stock, both packaged in trays for production use.