Barrel Power Jack

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Barrel Jack

This is the basic barrel power jack. Commonly used with wall-warts to get power onto your board. These come in a variety of sized. 5.5mm OD with a 2.1mm ID (the pin in the middle) is a common size. For DC systems, you also have to know the polarity : center positive means the center pin is positive and the outer shield is grounded; center negative means the center pin is grounded and the outer shield is positive. I've always used center positive for DC systems. This connector and many other stereo type connectors have more than just two connections. For most applications, one pin on the connector goes to the center pin, one to the shielding. The final pin on the connector is part of a switch. When there is no barrel inserted into the connector, the switch is open. When a barrel is inserted, the switch is closed. I used to mess this up a lot, something the ground would be disconected, so I now always tie these two pins together on the PCB (both go to ground as shown in the schematic).

example power supply

Common configuration:

Barrel Jack for 10-15V unregulated from a wall-wart
Reverse polarization Reverse Protection Diodes (1Amp is usually sufficient)
Power Switch
10-100uF decoupling (25-30V rated caps)
LM317, LM1117, LM7805, etc for the voltage regulation (make sure the v-reg can handle 10-15V input)
10uF and 0.1uF decoupling for Vcc on the far end of the v-reg

SFE Footprint Library

FP Name: Power Jack

Manufacturer Info:
CUI part # : PJ-202A

Supplier Info:
Digikey part # : CP-202A-ND
Single Piece Price : $0.38

Related Items:
Wall warts, voltage regulators, etc

Original Creator: --Sparkfun 16:40, 28 January 2006 (PST)

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