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Project Specification — 12V Power Distribution Block
Project Overview
  • Status: Draft
  • A 50 mm × 100 mm PCB for distributing a 12V DC input to barrel-jack outputs and 3-pin fan connectors.
Intended Use
  • Prototype / utility power distribution board for low-voltage 12V devices and fans.
  • Not intended for mains voltage on the PCB.
What the Device Should Do
  • Accept 12V DC through one 5.5×2.5 mm barrel input connector.
  • Distribute the 12V bus to four 5.5×2.1 mm barrel output connectors.
  • Distribute the same 12V/GND bus to four 3-pin fan connectors.
Main Features
  • One 12V DC input connector.
  • Four DC barrel output connectors.
  • Four 3-pin fan connectors using +12V, GND, and an unconnected tach/sense/control pin unless later specified.
  • Shared high-current copper bus for 12V and GND.
System Architecture
Diagram



  
    
  
  
    
  




















"5.5×2.5 mm DC Input<br/>12V, node_10A max"
"12V / GND Bus"
"5.5×2.1 mm Output 1<br/>2A max"
"5.5×2.1 mm Output 2<br/>2A max"
"5.5×2.1 mm Output 3<br/>2A max"
"5.5×2.1 mm Output 4<br/>2A max"
"3-pin Fan 1<br/>12V/GND"
"3-pin Fan 2<br/>12V/GND"
"3-pin Fan 3<br/>12V/GND"
"3-pin Fan 4<br/>12V/GND"
Hardware Subsystems
  • Power input: 5.5×2.5 mm DC barrel jack, rated for at least 10A if a suitable part is available.
  • Power outputs: four 5.5×2.1 mm barrel jacks, each intended for 2A maximum.
  • Fan outputs: four 3-pin fan headers tied to 12V and GND; third pin is currently not connected.
  • PCB copper: 12V and GND should use wide traces and/or copper pours sized for 10A total input.
Interfaces and Connections

Table

InterfaceQuantityConnection
5.5×2.5 mm DC barrel input1Center positive assumed: +12V center, sleeve GND
5.5×2.1 mm DC barrel output4Center positive assumed: +12V center, sleeve GND
3-pin fan connector4Pin 1 GND, Pin 2 +12V, Pin 3 NC/Tach TBD
Power and Runtime Expectations
  • Input: 12V DC nominal.
  • Total input current budget: 10A maximum.
  • Each output connector current budget: 2A maximum.
  • No battery or runtime constraint.
Power Tree and Power Budget

Table

RailSourceLoadsMax Current
+12VDC input jack4 barrel outputs + 4 fan connectors10A total
GNDDC input sleeveReturn for all outputs10A total return
Manufacturing and Assembly Expectations
  • Board size: 50 mm × 100 mm rectangle.
  • Suggested stackup: 2-layer PCB with large top/bottom copper pours for 12V and GND.
  • Connectors should be placed on long board edges: input on one long side, four barrel outputs on the opposite long side.
Firmware-Relevant Hardware Requirements
  • None currently; no controller is included.
Physical Design Expectations
  • 50 mm × 100 mm board.
  • Input barrel jack on one long side.
  • Four output barrel jacks on the opposite long side.
  • Four fan connectors accessible from the board edge or near the output side.
Important Design Decisions
  • Center-positive barrel polarity is assumed.
  • The third fan connector pin is left unconnected until tach/PWM behavior is specified.
  • Trace/pour sizing should be conservative for 10A total current.
Assumptions
  • All connectors are PCB-mounted through-hole parts unless library availability requires otherwise.
  • Barrel connectors are center-positive.
  • No fuses, switches, LEDs, reverse-polarity protection, or per-output protection were requested yet.
Change Notes
  • Initial requirements captured: 12V input, 10A total input, 2A per output, 50 mm × 100 mm PCB, one input jack, four output jacks, and four 3-pin fan connectors.

  • Project Overview

  • Intended Use

  • What the Device Should Do

  • Main Features

  • System Architecture

  • Hardware Subsystems

  • Interfaces and Connections

  • Power and Runtime Expectations

  • Power Tree and Power Budget

  • Manufacturing and Assembly Expectations

  • Firmware-Relevant Hardware Requirements

  • Physical Design Expectations

  • Important Design Decisions

  • Assumptions

  • Change Notes