Small Project Power Supply

Anyone know what the smallest (space) circuit for powering a core from 240V Mains might be ?

You’ll want some kind of switch-mode power supply (SMPS). They’re not the simplest circuits:

Are you thinking about an implementation in your own product designed to manufacture at scale, or your own project for personal use? If it’s a project, your best bet is probably to use a small Apple/Samsung style USB charger.

I’m looking for the same thing in a personal project. Although, I’d rather forego the USB connectors since they take up a lot of room. I just need the 110VAC converted to 5VDC with reasonably secure prongs on the AC side of things (optional as I’m not afraid to cut the plug off an extension cord). The Samsung and Apple power supplies in the first link look to be the best and smallest, but they aren’t exactly the cheapest.

I’m wondering what the smart guys* think — @BDub, @bko, @peekay123

* I’m not suggesting that folks not in the list are not smart; I just have more interaction with them!

i got this UL listed universal input (90-240VAC) at WalGreens for $10. They have some slightly bigger that are $8, but they are ETL listed. For your purposes either will be ok, but I personally go for UL listed power supplies :wink:

5V 1A output, with blue LED.

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I like and use the Apple USB supplies. The WalGreen’s one above looks fine too. For a lot of stuff I scrounge old cell phone power supplies. In the photo below, power is coming in from +5V 700mA Blackberry charger that I cut the end connector off of and soldered some pins on:

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I don’t know why I didn’t think of gutting a cell phone charger. I’m just spoiled by USB, I guess. I have an old Nokia charger that was powering my outdoor lighting relay before it got all :spark:ed up. :wink:

However, the next time I’m in Walgreens, I’m going to see what their charger selection is like.

Thanks @bko and @BDub!

It’s usually all up at the register. Nothing spectacular :smile:

My daughter now has pink eye, so I got to make an 11:00 PM run to my local Walgreens. Unfortunately, the only smallish USB power supplies they had started at $20.

They did have the LR44 batteries I needed for my digital calipers! I can measure tiny stuff again!

Hey guys,

if you want to create your own board in future and would like to have your own Power module,

take a look at all these. All squeezed into one module and you need minimal parts to complete the entire circuit.


Those are great @kennethlimcp but also way too expensive for most people.

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Ouch on cost! I’m thinking less than $10 USD.

It’s the modular way and like you guys, i don’t really love it but if there’s some projects in future that i need the power supply to be on board…i might try it out!

But i always wanted to design on myself ^^


In the US, try this one for $5.95.

As my Grandma used to say, “You can’t beat that with a stick!” :smiley:

UL listed and I love that Limor dialed up the voltage to the USB max of 5.25 to account for any voltage drop.


I actually have 3 or 4 of those. One is being used as a stand-in right now until I can find something smaller. It’s still 4x the size of the small Apple one, though. :-/

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I found this at a CVS Drugstore tonight–$5 for the USB supply and $5 for the micro USB cable, both of which work great with Spark:

They had $10 iPad 2A USB chargers as well. They are both UL listed.


Thanks for the find! I’ll hit up CVS tomorrow. There’s one conveniently across the street from our favorite Mexican restaurant.


$5 is practically free. Grandma can try to beat that one with a stick and fail miserably!

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What about one of these

Pretty cheap but would require some ac insulating

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