Hello,
I am working on a project consisting of developing an Arduino controlled power outlet, and have attached my current setup.
Currently, Arduino is only able to receive power if plugged into a wall socket or computer via adapter.
I am wondering if I can split my AC power cable to supply power to both the receptacle, and the Arduino.
I presume that converting 120V (Mains) to 5V is necessary. Would a step down converter be able to achieve this?
Please let me know if I missed anything.
Most duplex outlets sold in the USA can be split into two single outlets, It looks like you did that. Wire one to power your controller the other that you control probably with a relay. As you indicate you want two outlets then use a quad box which will accept two duplex outlets. Best keep the relay insulated and in the power box for safety. You must use at least 300 volt wire for the 115 power. It is required that the low voltage insulation be equal to or greater then the mains power when mixed in a non isolate box. Yes I do this a lot! This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil
cmpscimjr:
I presume that converting 120V (Mains) to 5V is necessary. Would a step down converter be able to achieve this?
No, a step down converter cannot convert from 120VAC to 5DC. You need a AC to DC power supply. These are also available as components not just plug in adapters. Depending on the power requirements you can get different sizes and shapes.
Hi,
Welcome to the forum.
Please read the post at the start of any forum , entitled "How to use this Forum".
OR
http://forum.arduino.cc/index.php/topic,148850.0.html.
OPs diagram;
Tom... 
The hots are not connected. The bottom outlet has no hot. Is that just a schematic error ?
Are they jumpered on the outlet ?
You can use relays but they are going to arc internally and eventually will fail. You should consider using
solid state relays instead. What kind of devices will be plugged into the outlets ?
Breaking a grounded neutral with a switch and leaving the HOT connected is a NO NO.
Good catch. I wasn't paying attention.
Yeah, like he said DON'T DO THAT !
"I presume that converting 120V (Mains) to 5V is necessary. Would a step down converter be able to achieve this?"
A simple approach to getting 5v from a wall outlet using a USB wall charger.
gilshultz:
Most duplex outlets sold in the USA can be split into two single outlets, It looks like you did that. Wire one to power your controller the other that you control probably with a relay. As you indicate you want two outlets then use a quad box which will accept two duplex outlets. Best keep the relay insulated and in the power box for safety. You must use at least 300 volt wire for the 115 power. It is required that the low voltage insulation be equal to or greater then the mains power when mixed in a non isolate box. Yes I do this a lot! This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil
I have considered powering the Arduino microcontroller using one of the outlets and will look into purchasing a quad receptacle. I will also make sure that the relay is insulted inside the outlet housing.
raschemmel:
The hots are not connected. The bottom outlet has no hot. Is that just a schematic error ?
Are they jumpered on the outlet ?You can use relays but they are going to arc internally and eventually will fail. You should consider using
solid state relays instead. What kind of devices will be plugged into the outlets ?
This is indeed a schematic error and is fixed below. Devices such as small desk-side lamps will be plugged into the outlets. I will look into using a solid-state switch.
zoomkat:
"I presume that converting 120V (Mains) to 5V is necessary. Would a step down converter be able to achieve this?"A simple approach to getting 5v from a wall outlet using a USB wall charger.
I have considered going with this approach, however, as I would eventually like to have this in a compact housing behind a wall, I was hoping to remove the need for a separate USB wall charger.
Please see the updated wiring schematic below. I have included a 110V to 12V power supply transformer adapter to hopefully allow for splitting Mains power between both outlets, and the Arduino microcontroller.
"I have considered going with this approach, however, as I would eventually like to have this in a compact housing behind a wall, I was hoping to remove the need for a separate USB wall charger."
I'd keep every thing outside the wall to avoid possibly having electrical code issues and difficulty in installation. I got the wall charger at the DollarTree for $1, so dig into it to see how large the internals are. Also depending on what is in the Monday truck, they have six outlet plug in receptacles and short three outlet poser strips. You might consider putting your project in these instead of in the wall.
JCA34F:
Breaking a grounded neutral with a switch and leaving the HOT connected is a NO NO.
Hot/live and neutral have no real meaning in this when you're using EU or US style plugs which are reversible. So you never know which of the two is actually the live and which one the neutral.
As a former land lord, I have to ask you if you are renting the property or do you own it? If renting, expect the landlord to complain loudly the next inspection!
Paul
Have a look for PCB power supplies to power your Arduino. You can find them on Digikey for instance.
https://www.digikey.com/products/en/power-supplies-board-mount/ac-dc-converters/923
Wall sockets with USB outlets are becoming common.
Perhaps consider swapping out a couple of outlets for a couple of these.
Personally, I'm using extension strips with USB outlets, and have other things plugged into the strip, such as a wall light timer, my computer power supply, my 3D printer.
wvmarle:
Hot/live and neutral have no real meaning in this when you're using EU or US style plugs which are reversible. So you never know which of the two is actually the live and which one the neutral.
Not really, the convention in the US is that the blade sizes are different. When it matters, two wire cords/plugs are always polarized with different sized blades. No device with a UL label will have the same size blades.
The narrow side as shown in the OP’s image (the right side) has brass colored screws and is the hot or line side and is connected to the black wire (blue wire in a cord-set).
The left, wider side is the neutral, has white screws and is connect to the white wire (brown in a cord-set).
Green is of course ground and as already mentioned NEVER SWITCH THE NEUTRAL.
If you don’t understand what you’re doing with mains voltage and it looks like you don’t, save a life, which may be your own, and buy one of these:
I'm not an electrician but I was told Neutral is tied to ground (or vice versa at the main box and it is for human safety and would not be necessary
if no humans were on site. Point being, the reason why you should switch the hots is so if there is a short it will be shunted to ground, tripping the breaker. Switching neutral eliminates the human safety protection and someone could be electrocuted.
Neutral is supposed to be connected to ground - well, more than that: neutral IS ground for the part between your home and the power plant, literally, as the earth itself is the return. That's why power lines always come in threes, the phases, without ground return. In fact if all phases are loaded equally there is zero current in the neutral, but as that in reality never happens there is always some current flowing.
Nonetheless European style plugs are reversible, so maybe it's not that big a deal which side is switched. After all you must always unplug a device from the power before opening it... even if it's powered off...
WattsThat:
The narrow side as shown in the OP’s image (the right side) has brass colored screws and is the hot or line side and is connected to the black wire (blue wire in a cord-set).The left, wider side is the neutral, has white screws and is connect to the white wire (brown in a cord-set).
Don't think so. 
IEC standard is that brown is the "live" or "hot" side, and blue is neutral. 
WattsThat:
hot or line side and is connected (blue wire in a cord-set).The left, wider side is the neutral, (brown in a cord-set).
Interesting, that is the exact opposite of harmonised Euro and UK codes, brown live, blue neutral and green/yellow is earth. Our three pin standard plugs cannot be reversed, however the Shuko European plugs come in two flavours, three pin and reversible two pin for non earthed devices.
AJLElectronics:
Interesting, that is the exact opposite of harmonised Euro and UK codes, brown live, blue neutral and green/yellow is earth.
As I had just pointed out.
