120 volt ac to 5 volt dc circuit?

How to build the circuit that is in those devices that plug into 120 volt receptacle and can have a usb charger cable plugged into it. I just need the circuit diagram. I am a little familiar with schematic reading. It all fits in that little plug in device, so it can't be that much, right?. Thanks.

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NorbertoB33 months ago

i have a kitchen bulb go out, removing the cover i seen the wires are just connected to the bulbs housing case that the bulb goes pluges/screwed onto. i also have arduino running off a 5volt power converter like the usb type that you plug into the wall, its been running my led setup since day1 on 24/7, i see no risk in removing kitchen bulb setup and soldering it straight into the terminals were the 5volt dc converter connects to the wall and running my leds straight from the kitchen switch lighting lready in place....just as if it was two female leads from a wall socket, but backwards, the wires from the 120v AC would prong into the 5volt wall adapter

....what do yall think about this tho!!!

DraakUSA11 months ago

In case anyone is still interested; here is a teardown of the Apple charge cube.


When you start messing with mains power you better know what your doing. I think you should leave the mains power conversion to an existing wall plug you already have and use this to give yourself USB power. If you feel you just have to make this yourself.


stevecinstrfme (author)  mpilchfamily2 years ago
I appreciate your response, and I can appreciate the safety concerns, however, I am an electrician and I understand mains power and all that goes with that, but have yet to learn more in the way of electronics. As I wrote to another comment, this was more or less my curiosity on how it is done. I'm not sure I will attempt to build it; just wanted to see the schematic first. Also, I did look at the instructable you mentioned, however, I don't want to go from a "wall wart" to usb, I need to know how to go from 120 volts ac to usb, just like what is in the device mentioned. Thanks again.

Well the smaller devices use a Switching Mode Power Supply (SMPS). You can google the schematics for one. The larger older style ones use a 120VAC to 12VDC transformer, rectify it to DC using a bridge rectifier then run that 12VDC through a 5V voltage regulator like a 7805. Of course you'll find other bits like filter caps and whatnot to help clean up the noise from the AC line.

Pretty much any kind of basic shematic you want to find will come up in a google image search. So searching '120VAC to 5VDC switching power supply schematic' will give you what your looking for. The SMPS's are rather more complicated than your basic transformer and rectifier setup. But they can fit into a smaller housing and are much more efficient.

Don't. They cost so little, and the consequences of being wrong are so critical, its really not worth it.

stevecinstrfme (author)  steveastrouk2 years ago
I appreciate yours and every one elses comments on safety and the fact that they cost very little, however, I would still like to see the schematic for it and I will consider whether I will tackle it or not. It was basically just curiosity. Thanks again.

How its done is the way all SMPSUs work.
AC is rectified to DC, at high voltage, chopped up at high frequency,
and passed through a transformer: because the frequency is high, the
transformer can be very small (and cheap). The output is then rectified
to DC, and smoothed with capacitors, which are smaller than the ones
we'd use in a mains transformer.

There's a wrinkle in the smaller ones, because unlike forward converter topologies, they use the elegant flyback technique, where power is stored in the magnetic field in the core.



seandogue2 years ago

I'd recommend purchasing one and dismantling it. All I can say is how *I might design one, which isn't what you want.. I'm not exactly sure how the actual mfg's do it.

And no, I doubt there'a ll that much involved or they couldn't sell them for a couple of dollars. "generalistically", it's line to transformer to rectifier to cap to regulator to cap to output in the way you'd already be familiar. The specifics of how they accomplish that is the cloaked part for me, as I've never depotted one.

iceng2 years ago

Easier to buy for 99 cents at the dollar store...