Power Supplies for your Project

Updated 28 November 2016

Ever had the issue where you have dozens of old phone chargers and appliance plug packs piled up in a rats nest of AC-to-DC mayhem? We tend to breeze right past these square, black power supplies, not knowing what's happening under the hood. Plug Packs, Wall-Warts AC-DC converters or just old' fashioned power supplies; call them whatever you'd like, they are ridiculously practical things to have around. Taking the 240V AC power from the wall socket and turning it into the quaint 5V 1A your phone needs to charge is among many of their essential uses. They aren't just charging phones either; another fantastic usage is to power a home-made circuit/project from the wall, especially if there is no need for it to be portable.

power-supply for label

Our first choice when it comes to powering workshop inventions is a high-quality Benchtop Power Supply; these things are king when it comes to versatile options for powering your circuit. If that’s the avenue you’re looking to go down, look at our article on benchtop power supplies. If the idea of a simple barrel jack wall wart is more appealing to you, read on and perhaps consider a few of our Solderless Breadboard Power Supply options alongside a decent switching plug pack.

There're a few things to learn when it comes to your wall wart power supplies. Input voltage is what you can connect your supply into, in our example we see that is 100-240V AC oscillating at 50-60Hz, and it will draw 100mA max. That amount of input power will convert into a 9V DC supply up to 210mA of current. When finding a power supply for our circuit, we have to match the voltage value of the circuit/supply. For current supply, we only need to ensure there is enough current supplied so that the circuit will run. If you wanted a great run down on Ohms Law and other electronics related theoretical discussion, check out Sam's write-up on Analog Electronics.

Usually, we use barrel jacks as the terminations for our power supplies, and they are ideal connectors for a few reasons. The first being that they only have two connections, Vcc and Ground; meaning the termination can only be connected two possible ways. We call those two orientations centre-positive and centre-negative polarities, they can be found on the label of your wall-wart as one of the two following depictions:



There are a few sizes available of DC barrel jack too, and we tend to see them described by one of their two measurable diameters. The inner diameter (ID) or outer diameter (OD). A universal plug we see frequently is the 2.1mm (ID) and 5.5mm(OD) connection, also known as the Type A Connector from the IEC plug standards.

Luckily for us, the people over at Sparkfun & Adafruit have a myriad of female and male DC barrel jack adapters that we can use for terminating cables.

We've gone ahead and stocked a manually selectable 3-12V DC Wall Wart, capable of supplying 2250mA current. The cable is terminated with a regular USB female plug, meaning you can connect any USB device up to it; additionally, this plug pack comes with seven different male barrel jack adaptors, covering you in a wide range of applications. There are fixed output supplies available too; but why not get something that is multi-purpose? You'll never be rummaging through that drawer full of mismatched wall warts ever again with this 

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