Wall Power Adapter: 5VDC, 3A, 5.5×2.1mm Barrel Jack, Center-Positive

via Pololu
$17.69
SKU PL-1461

This UL-certified (file number EPBU.E477038) AC-to-DC converter gives you an easy way to power your DC electronics project from a US-style AC electrical socket. It uses a switching regulator to efficiently output up to 3 A at a near-constant regulated 5 VDC, even when no load is applied. The DC power cable is 5 ft (1.5 m) long and terminated with a center-positive, 5.5 × 2.1 mm barrel connector that works with the DC power adapter barrel jack as well as the barrel jack on many Arduinos and the BASIC Stamp discovery kit (we recommend the 9VDC 1A version for powering these two particular devices).

We have wall power adapters available in a range of voltages and maximum output currents: