RI-25B Reed Switch Equivalent & Substitute Parts

Part Overview

The RI-25B is a glass body reed switch manufactured by Comus International, classified as SPST-NO (Single Pole Single Throw - Normally Open) with a rated switching capacity of 1A at 140V AC. This component is designed for through-hole mounting applications requiring low-power switching control. The RI-25B is currently listed as obsolete, making identification of compatible substitute parts essential for ongoing maintenance, repair, and legacy system support.

Substiute Parts

RI-25B

Comus InternationalIn Stock: 937RI-25B Datasheet

Current PartRFQ

MLRR-3-32-38

Littelfuse Inc.In Stock: 2501MLRR-3-32-38 Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the RI-25B reed switch is determined by strict alignment of the following electrical and mechanical parameters:

Critical Substitution Criteria:

1. Circuit Configuration: Both parts must be SPST-NO to maintain identical switching logic and pin functionality.

2. Voltage Rating: The substitute must support minimum 140V AC switching voltage to ensure compatibility with existing circuit designs.

3. Current Capacity: The substitute must handle the required switching current. The RI-25B switches 1A (AC/DC); substitutes with 700mA AC and 1A DC capability remain compatible when AC operation does not exceed 700mA or DC operation does not exceed 1A.

4. Mounting and Termination: Both parts must use through-hole mounting with axial termination to ensure PCB compatibility without redesign.

5. Power Rating: The substitute power rating must meet or exceed the application requirement. The RI-25B is rated 25W; substitutes rated 20W are acceptable when actual circuit power dissipation does not exceed 20W.

6. Operating Temperature: The substitute must cover the required temperature range. The RI-25B operates -55°C ~ 125°C; substitutes with -40°C ~ 125°C are acceptable for applications not requiring sub-zero operation below -40°C.

7. Compliance Standards: Both RoHS and REACH compliance status must be verified for regulatory requirements.

The MLRR-3-32-38 from Littelfuse Inc. meets these substitution criteria with the noted current and temperature limitations.

Parameter Comparison

Engineering Selection Recommendations

Substitution Feasibility:

The MLRR-3-32-38 (Littelfuse Inc.) is a valid substitute for the obsolete RI-25B under the following conditions:

1. Current Application Profile: If the application operates at AC currents not exceeding 700mA or DC currents not exceeding 1A, the MLRR-3-32-38 is electrically compatible. If the original design requires 1A AC switching, the MLRR-3-32-38 is not suitable.

2. Power Dissipation: If actual circuit power dissipation does not exceed 20W, the MLRR-3-32-38 meets power requirements. Applications requiring the full 25W rating of the RI-25B must be evaluated for power margin.

3. Temperature Environment: If the application operates within -40°C to 125°C, the MLRR-3-32-38 is compatible. Applications requiring operation below -40°C require alternative substitutes.

4. Physical Space: The MLRR-3-32-38 is 0.419" (10.64mm) longer than the RI-25B. PCB layout must accommodate this increased length without component interference.

5. Regulatory Compliance: Both parts maintain RoHS and REACH compliance, suitable for regulated markets.

Active Product Status Advantage:

The MLRR-3-32-38 is currently in active production status, ensuring long-term availability and supply chain stability compared to the obsolete RI-25B.

Frequently Asked Questions (FAQ)

Q: Can the MLRR-3-32-38 directly replace the RI-25B in all applications?

A: No. The MLRR-3-32-38 has lower AC current rating (700mA vs. 1A) and lower power rating (20W vs. 25W). Direct replacement is only valid when actual application current and power requirements fall within the MLRR-3-32-38 specifications.

Q: What is the primary difference between these two reed switches?

A: The RI-25B is obsolete and manufactured by Comus International, while the MLRR-3-32-38 is an active product from Littelfuse Inc. Both are SPST-NO glass body reed switches with identical voltage ratings, but the MLRR-3-32-38 has reduced AC current capacity and power rating.

Q: Does the longer length of the MLRR-3-32-38 affect compatibility?

A: Physical length difference (1.811" vs. 2.230") requires PCB layout verification. If the original RI-25B footprint allows the additional 0.419" length without component collision or spacing violations, the MLRR-3-32-38 can be accommodated. Otherwise, alternative substitutes must be evaluated.

Q: Are both parts RoHS compliant?

A: Yes. The RI-25B is RoHS Compliant, and the MLRR-3-32-38 is ROHS3 Compliant. Both meet current RoHS requirements.

Q: What is the operating temperature limitation of the MLRR-3-32-38?

A: The MLRR-3-32-38 operates from -40°C to 125°C, compared to the RI-25B range of -55°C to 125°C. Applications requiring operation below -40°C cannot use the MLRR-3-32-38.

Q: Can I use the MLRR-3-32-38 if my circuit requires 1A AC switching?

A: No. The MLRR-3-32-38 is rated 700mA AC maximum. Using it in a 1A AC application exceeds its switching current specification and may result in contact degradation or failure.

Q: What should I do if the MLRR-3-32-38 does not meet my application requirements?

A: Consult the complete equivalent parts database for alternative SPST-NO reed switches with matching voltage, current, power, and temperature specifications. Littelfuse and other manufacturers offer additional reed switch series that may provide better parameter alignment.