DC Power

Few things are more frustrating than a DC plug that almost fits. Our own TruConnect range covers the barrel plugs, sockets and jacks people need most, in the common sizes and every mounting style, so it's the natural place to start.

Measure twice: outside diameter, pin and barrel length

A barrel connector is described as outside diameter x pin diameter, so 5.5 x 2.1mm is a 5.5mm barrel on a 2.1mm centre pin. That size and 5.5 x 2.5mm are the two you'll meet most, and they look almost identical. Get them the wrong way round and a 2.5mm plug sits loosely on a 2.1mm pin and cuts out when it's nudged, while a 2.1mm plug simply won't go onto a 2.5mm pin. Measure the pin, or check the equipment's documentation, before you order.

Barrel length matters too. If the socket sits behind a thick case wall, a short plug may not reach far enough to make contact.

Polarity and switched sockets

Most equipment is centre-positive, but not all of it, and reversing the polarity can destroy a circuit instantly. The symbol near the inlet shows which way round it is. Many sockets also have a third, switched contact that changes over when a plug goes in. It's a simple way to disconnect an internal battery when an external supply is connected, and it's worth designing in from the start.

Choosing the mounting

Cable-mount plugs and inline sockets make up leads and extensions. Panel-mount sockets fix through an enclosure wall and take the strain of repeated plugging away from the circuit board. PCB jacks are compact and cheap to assemble, but they rely on their solder joints and mounting tabs, so they suit equipment that isn't unplugged every day. Where vibration or accidental pulls are a risk, a locking connector is worth the small extra cost.

TruConnect: the obvious first stop

For everyday DC connectors, our own TruConnect range fits and performs like the branded parts it replaces, and it covers the sizes that get used most.

DC connector questions

Is a "2.1mm" connector the same as 5.5 x 2.1mm?

Usually, because 2.1mm normally refers to the pin and 5.5mm is the most common outside diameter. It isn't a given, though. Smaller barrels such as 3.5 x 1.3mm exist too, so always confirm both figures.

What current can a barrel connector carry?

It depends on the size and design. Miniature barrels are typically rated for an amp or two, and full-size 5.5mm types for a few amps. Check the rating on the product page and allow some headroom, because a warm connector is usually a sign it's working too hard.

Can I use a DC barrel connector for mains voltage?

No. They're designed for low-voltage DC only. For mains, use an IEC inlet or a connector rated and approved for mains, from our power connectors range.

Why does my plug fit but the device won't power up?

Check three things: the pin size (a loose fit can make no contact at all), the polarity, and whether the socket's switched contact has been wired by mistake so that inserting the plug cuts off the supply instead of the battery.

Do PCB-mount DC jacks need extra support?

If they'll be plugged in often, yes. Choose a jack with through-hole mounting tabs, or mount the socket on the panel and wire it to the board, so the force of plugging and unplugging doesn't end up on the solder joints.