Connector Corner

February 6, 2019

All About Circular Connectors: Mil-Spec Design Summary

This blog post is written to fulfill every design engineer’s dream – all about the circular mil-spec connectors in one place. In the following article, we focus on describing the elements of the most common circular mil-spec connector series in order to make your designing job easier. Application notes and illustrations describe key mechanical aspects of each series.

MIL-DTL-5015 (SAE AS50151) connectors, circular, MS3100 series (solder contact)

 

Design Features:

  • Threaded coupling design; eight connector configurations.
  • Fifteen shell sizes—Range 8 thru 48 (.500" to 3.000" diameter).
  • Wide variety of power and signal contact sizes (#4/0 to #20), standard density; 1 to 100 contacts.
  • Conductive finish—Cadmium/Olive drab, 96-hour corrosion protection (standard).

Application Notes:

  1. Contacts may mate prior to connector shell mating.
  2. Single keying may not always ensure shell polarizing.
  3. Uncontrolled accessory interface.
  4. Plug or receptacle may have pin or socket contacts.
  5. Connector shell may strike pin contacts; thus, power should always be on socket contacts.

MIL-DTL-26482 connectors, circular MS3110 and MS3116 Series 1 (solder contact)

 

Design Features:

  • Bayonet coupling, quick disconnect plug and receptacle
  • Ten shell sizes—Range 6 through 24 (.3750" to 1.500" diameter).
  • 3 to 61 standard density #12, #16, and #20 contacts.
  • Conductive and non-conductive finishes; Cadmium/Olive drab and anodic.

Application Notes:

  1. Contacts may mate prior to connector shell mating.
  2. Plug may have less than three threads.

MIL-C-26482 Connectors, Circular, MS3120 and MS3126 Series 1 (front-release crimp contacts)

 

Design Features:

  • Bayonet coupling, quick disconnect plug and receptacle.
  • Eight shell sizes—Range 8 thru 24 (.500" to 1.500" dia.)
  • 3 to 61 standard density #12, #16, #20, and #22 contacts.

Application Notes:

  1. Contacts may mate prior to connector shell mating when grounding fingers not supplied.
  2. Same limitations as MS3110/MS3116 solder connectors.
  3. Uncontrolled wire seal grommet geometry; accessories properly mate.

MIL-C-26482 Connectors, Circular, MS3470 Series 2 (rear-release crimp contacts)

 

Design Features:

  • Bayonet coupling design, quick disconnect. Seven receptacle designs and two plug designs (including RFI shielded).
  • Nine shell sizes—8 through 24 (.500" to 1.500" dia).
  • 3 to 61 standard-density #12, #16, #20, and #22 contacts.

MIL-DTL-28840 Connectors, Circular (front-release crimp contacts)

 

Design Features:

  • Threaded coupling design, rapid advance, captive, scoop proof; five connector designs
  • Nine shell sizes—Range 11 through 33 (.500 to 2.000 diameter).
  • 7 to 155 #20-gauge high density contacts.

MIL-DTL-38999 Connectors, Series I (rear-release crimp contacts)

Design Features:

  • Bayonet coupling design, quick disconnect.
  • Nine shell sizes—Range 8 through 24 (.500" to 1.500" diameter); twelve connector styles.
  • #8, #10, #12, #16, #20, and #22 standard-density; #22 high-density arrangements; 3 to 128 contacts.
  • Scoop-proof shell design to prevent shell-to-contact problem.
  • Controlled accessory interface per MIL-DTL-38999, figure II.
  • Cork-and-bottle primary insert interface seal and shell environmental seal, fuel-resistant silicone elastomers.
  • Conductive and non-conductive finishes; electroless nickel, Cadmium/Olive drab 500-hour salt spray, and anodic.

Notes:

  1. Long scoop-proof barrel design to prevent shell striking contacts.
  2. Serrated accessory interlocking tooth design may prevent reliable moisture seal or EMI bond to accessories.
  3. Bayonet coupling may not perform under severe conditions with large diameter cable and backshell.

MIL-DTL-38999 Connectors, Series II (rear-release crimp contacts)

Design Features:

  • Bayonet coupling design, quick disconnect, captive.
  • Nine shell sizes—Range 8 through 24 (.500" to 1.500" diameter); Fifteen connector designs.
  • #16, #20, and #22 contacts, standard density and #22 high-density arrangements; 3 to 128 contacts.
  • Shell ground available on MS and commercial part numbers.
  • Controlled accessory interface per MIL-DTL-38999 fig. II.
  • Cork-and-bottle primary interface and shell environmental seals, fluid-resistant silicone elastomers.
  • Conductive and non-conductive finishes; electroless nickel, Cadmium/Olive drab, 500-hour salt spray, and anodic.
  • Short barrel construction for minimum envelope.

Notes:

  1. Very short barrel,
  2. shell may strike pin contacts. 2.
  3. Wire seal grommet controlled to maximum condition only, over compression will cause contact splaying.
  4. Same limitations as D38999 Series I.

MIL-DTL-38999 connectors, Series III circular, rear-release crimp contacts

Air Electro offers value added assembly for D38999 Series III from both Souriau and Corsair.

Design Features:

  • Threaded coupling design, rapid advance, self-locking.
  • Nine shell sizes—Range 9 through 25 (.500" to 1.500" diameter). Thirteen connector designs.
  • #8, #10, #12, #16, #20, and #22 contacts, standard density and #22 high-density arrangements; 3 to 128 contacts.
  • #16 fiber-optic insert arrangement.
  • Scoop-proof shell design to prevent shell to contact problem.
  • Controlled accessory interface with metric threads.
  • Diaphragm contact seal interface and shell environmental seal, fluid resistant fluorosilicone elastomers.
  • Conductive and non-conductive finishes; Cadmium/Olive drab 500-hour salt spray, electroless nickel, anodic and stainless steel.
  • Conductive composite shell, cadmium/olive drab over electroless nickel, and electroless nickel, 2000-hour salt.

Notes:

  1. Same accessory mating interface as MIL-DTL-38999 Series I, except metric threads.
  2. 100 percent scoop proof, positive shell mating.

MIL-DTL-38999 connectors, Series IV circular, rear-release crimp contacts

Design Features:

  • Breech lock coupling design, rapid advance, self-locking.
  • Eight shell sizes—Range 11 through 25 (.500" to 1.500" diameter).
  • #12, #16, #20, and #22 contacts, standard density and #22 high density arrangements; 3 to 128 contacts.
  • #16 fiber optic insert arrangements. „ Scoop-proof shell design to prevent shell-to-contact problems.
  • Controlled accessory interface with metric threads.
  • Ruggedized construction for shipboard service.
  • Cork and bottle primary interface and shell environmental seals, fluid resistant fluorosilicone elastomers.
  • Conductive and non-conductive finishes; Cadmium/Olive drab 500 hour salt spray, electroless nickel, anodic, and stainless steel.

Notes:

  1. 100 percent scoop-proof, positive shell mating.
  2. Same accessory interlock teeth as MIL-DTL-38999, Series III.
  3. Same O-ring seal features as MIL-DTL-38999, Series III.

Circular connectors are the most commonly used in mil-aero applications. We hope that this detailed description on design and feature capabilities of each commonly used series was helpful. If you like what you read, please post a comment and share on your social media or with your colleagues who might benefit by having this article as their bookmark.

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