RPI-129BN Equivalent & Substitute Parts

Part Overview

The RPI-129BN is an optical sensor phototransistor slotted module manufactured by Rohm Semiconductor. This component functions as an unamplified optical sensor with phototransistor output configuration, designed for through-hole mounting applications. The product is currently classified as obsolete, making identification of suitable substitute components essential for ongoing design support and production continuity. Active equivalent models are available from both the original manufacturer and alternative suppliers that maintain compatibility with the electrical and mechanical specifications of the original design.

Key Parameters

Parameter	Value
Manufacturer Part Number	RPI-129BN
Manufacturer	Rohm Semiconductor
Category	Optical Sensors
Description	Optical Sensor Phototransistor Slotted Module
Product Status	Obsolete
Output Configuration	Phototransistor
Current - DC Forward (If) (Max)	50 mA
Current - Collector (Ic) (Max)	30 mA
Voltage - Collector Emitter Breakdown (Max)	30 V
Response Time	10µs
Operating Temperature	-25°C ~ 85°C
Mounting Type	Through Hole
Package / Case	Slotted Module
Type	Unamplified
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitute components for the RPI-129BN are identified based on strict electrical and mechanical parameter alignment. The primary substitution criteria are:

Electrical Compatibility Parameters:

Output Configuration: Phototransistor (required match)
Current - DC Forward (If) (Max): 50 mA (required match)
Voltage - Collector Emitter Breakdown (Max): 30 V (required match)
Type: Unamplified (required match)

Mechanical Compatibility Parameters:

Mounting Type: Through Hole (required match)
Package / Case: Slotted Module (required match)

Compliance Parameters:

RoHS Status: ROHS3 Compliant (required match)
Moisture Sensitivity Level (MSL): 1 (Unlimited) (required match)

The RPI-125 (Rohm Semiconductor) qualifies as a direct substitute, maintaining identical electrical specifications and mechanical form factor while offering active product status. The OPB821Z (TT Electronics / Optek Technology) qualifies as a similar substitute with compatible core electrical parameters, though with differing collector current maximum specification and sensing distance characteristics.

Parameter Comparison

Parameter	RPI-129BN	RPI-125	OPB821Z
Manufacturer	Rohm Semiconductor	Rohm Semiconductor	TT Electronics / Optek Technology
Product Status	Obsolete	Active	Active
Output Configuration	Phototransistor	Phototransistor	Phototransistor
Current - DC Forward (If) (Max)	50 mA	50 mA	50 mA
Current - Collector (Ic) (Max)	30 mA	30 mA	500 µA
Voltage - Collector Emitter Breakdown (Max)	30 V	30 V	30 V
Operating Temperature	-25°C ~ 85°C	-25°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	Slotted Module	Slotted Module	Module, Slotted
Type	Unamplified	Unamplified	Unamplified
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

RPI-125 (Direct Substitute): This component is the primary recommended substitute for the obsolete RPI-129BN. It is manufactured by the same supplier (Rohm Semiconductor), maintains active product status, and provides identical electrical and mechanical specifications. All compliance certifications (ROHS3, REACH Unaffected) are equivalent. This substitute presents no design modification requirements.

OPB821Z (Similar Substitute): This component from TT Electronics / Optek Technology maintains compatibility with core electrical parameters and mechanical form factor. The collector current maximum specification differs (500 µA versus 30 mA), which may affect circuit performance in applications requiring higher collector current. The extended operating temperature range (-40°C ~ 85°C) provides additional thermal margin compared to the original specification. This substitute is suitable for applications where the lower collector current specification does not present a functional constraint.

Frequently Asked Questions (FAQ)

Q: Can the RPI-125 be used as a direct replacement for the RPI-129BN without circuit modification?

A: Yes. The RPI-125 maintains identical electrical specifications (50 mA forward current, 30 mA collector current maximum, 30 V breakdown voltage) and mechanical form factor (through-hole slotted module). No circuit redesign is required.

Q: What is the primary difference between the RPI-125 and OPB821Z substitutes?

A: The RPI-125 maintains the original 30 mA collector current maximum specification. The OPB821Z specifies a maximum collector current of 500 µA, which is significantly lower. Selection between these substitutes depends on the collector current requirements of the application circuit.

Q: Are both substitute parts RoHS compliant?

A: Yes. Both the RPI-125 and OPB821Z are ROHS3 compliant and carry MSL rating of 1 (Unlimited), matching the compliance profile of the original RPI-129BN.

Q: Does the OPB821Z sensing distance specification affect substitution compatibility?

A: Sensing distance is not a parameter specified for the original RPI-129BN. The OPB821Z specifies 0.080" (2.03mm) through-beam sensing distance. Substitution compatibility is determined by electrical and mechanical parameters. Application-specific sensing distance requirements must be evaluated independently.

Q: What is the moisture sensitivity level for these components?

A: All three components (RPI-129BN, RPI-125, and OPB821Z) carry MSL rating 1 (Unlimited), indicating no moisture sensitivity constraints for storage and handling.

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