RI-27AAA Reed Switch SPST-NO Equivalent & Substitute Parts

Part Overview

The RI-27AAA is a Glass Body Reed Switch with SPST-NO (Single-Pole Single-Throw Normally Open) configuration manufactured by Comus International. This through-hole mounted component is rated for 500mA at 130V AC (180V DC) with 10W power rating and operates within a 10–19AT range. The product has reached obsolete status, requiring alternative components for new designs and ongoing support of legacy applications.

Substiute Parts

RI-27AAA

Comus InternationalIn Stock: 987RI-27AAA Datasheet

Current PartRFQ

RI-27GP1015

Comus InternationalIn Stock: 1287RI-27GP1015 Datasheet

SimilarRFQ

MDSR-7-10-20

Littelfuse Inc.In Stock: 44222MDSR-7-10-20 Datasheet

DirectRFQ

MDSR-10-8-10

Littelfuse Inc.In Stock: 2226MDSR-10-8-10 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the RI-27AAA requires matching critical electrical parameters: circuit configuration (SPST-NO), current switching capacity (500mA AC/DC), voltage ratings (130V AC / 180V DC minimum), and power rating (10W). Mechanical compatibility includes through-hole axial termination. The operate range may vary between 8–20AT depending on the substitute, provided the operating point remains within specification. All candidates must maintain RoHS3 compliance or higher. Littelfuse MDSR series components provide direct functional equivalents with enhanced availability due to active product status, while the RI-27GP1015 from the same manufacturer series offers the closest parameter match.

Parameter Comparison

Engineering Selection Recommendations

RI-27GP1015 is the primary recommended substitute for the RI-27AAA. Both components are from the same manufacturer series, share identical voltage and current ratings, and operate at the same switching times (0.25ms operate, 0.03ms release). The RI-27GP1015 is currently in active production status with 1,178 units in stock, ensuring supply chain continuity. The operate range narrows from 10–19AT to 10–15AT, which is acceptable for applications within this narrower actuation window. RoHS3 compliance exceeds the original RoHS compliance requirement.

MDSR-7-10-20 and MDSR-10-8-10 from Littelfuse Inc. provide functional alternatives with higher voltage ratings (140V AC / 200V DC) and greater availability (44,188 and 2,200 units respectively). Both maintain the 10W power rating and support 500mA DC switching. The MDSR-7-10-20 operates within a 10–20AT range and is suitable for applications requiring the widest operate margin. The MDSR-10-8-10 covers the narrowest operate range (8–10AT) and is appropriate only for applications that do not require actuation above 10AT. Both Littelfuse options exhibit slightly longer switching times (0.5–0.6ms operate, 0.1–0.2ms release) compared to the original component. Littelfuse components are qualified for ROHS3 compliance.

Selection should be based on application-specific operate range requirements and supply chain considerations. The RI-27GP1015 minimizes design changes due to mechanical and electrical parameter alignment. Littelfuse options are selected when supply of Comus International components is unavailable or when enhanced voltage margins are required.

Frequently Asked Questions (FAQ)

Q: Can the RI-27GP1015 directly replace the RI-27AAA in existing designs? A: Yes. The RI-27GP1015 matches the RI-27AAA in all critical parameters except operate range, which narrows from 10–19AT to 10–15AT. No circuit modifications are required if the application operates within the 10–15AT window. The 1.811" length and axial termination are identical, ensuring mechanical compatibility in through-hole PCB layouts.

Q: What are the key differences between the Comus International and Littelfuse substitute options? A: Both Littelfuse options (MDSR-7-10-20 and MDSR-10-8-10) provide superior voltage ratings (140V AC / 200V DC vs. 130V AC / 180V DC). Component length is reduced from 46.00mm to 40.39mm, and body diameter is shorter in the MDSR-10-8-10 variant. Switching times are slower (0.5–0.6ms operate vs. 0.25ms operate). All three substitute parts maintain the same power rating, current capacity, and through-hole axial configuration.

Q: Which substitute should be selected if the original operate range (10–19AT) is critical? A: The MDSR-7-10-20 covers the 10–20AT range, which encompasses the original specification. The RI-27GP1015 does not—it operates only within 10–15AT. If the application requires actuation between 15–19AT, the MDSR-7-10-20 is the only qualified substitute from this list.

Q: Are there any compliance or packaging differences to consider? A: All substitute parts exceed or match the original RoHS compliance level (ROHS3 compliant). Packaging differs: RI-27GP1015 is supplied in bulk, MDSR-7-10-20 in bulk, and MDSR-10-8-10 in box format. MSL rating is identical across all options (MSL 1 - Unlimited). REACH and ECCN classifications remain unchanged.

Q: Is the lower DC current-carry rating of the Littelfuse options a concern? A: The MDSR-7-10-20 supports 800mA DC carry vs. 1.5A in the original; MDSR-10-8-10 supports 1A vs. 1.5A. Evaluate against application current requirements. If sustained DC currents exceed 800mA, the RI-27GP1015 is preferable (1.5A carry rating) or confirm that the Littelfuse option's 1A rating is adequate for the design.