A simple solution for powering up low-voltage DC devices in public spaces. When you plug this in, one of the plugs is powering an outlet on a decoy junction box and the other plug is providing a continual power source to a low-voltage DC device. This is something that I have been fiddling with for ages and it is not quite done, but I put it online due to the urging of some friends who find the information useful. Maybe you can figure out the final step (I will explain later).
PLEASE NOTE: This project uses high-voltages which are inherently dangerous. Additionally, I am not an electrician and can not verify if this project poses a fire-hazard. Lastly, I am pretty sure that the use of this project on other people's property would be illegal.
***Construct and use at your own risk.***
Step 1: Go get stuff.
You're going to need things to do this:
1. A standard wall socket
2. An outdoor socket cover
3. A cell phone charger (preferably 5V 500ma)
4. Two grounded wall plugs (like the one below)
5. A 1" x 2.5" piece of lucite that is of 1/8" thickness
6. Electrical tape
7. Thick stranded wire (the one below is from a strand of Christmas lights)
8. A plastic 1/8" pull-tie (not shown)
to be explained in final step:
9. Casing and paint (not shown)
10. Epoxy (not shown)
1. A Phillips-head screwdriver
2. A pair of pliers
3. A Dremel (or laser cutter)
4. A utility knife
5. Wire strippers
6. Soldering iron
Step 2: Make the plug bracket.
Okay, so the first thing you're going need to do is to make a bracket to mount your grounded wall plugs. This will hold them so that they can both plug into both outlet sockets at the same time.
The one you see was cut with a laser cutter that the Graffiti Research Lab was kind enough to let me use. I recommend begging, borrowing or stealing a laser cutter. Otherwise, you can use a Dremel to cut out the mounts. My first mount was done with a Dremel, so I know it's perfectly feasible. It will just take a little more work.
First take apart the plugs. Notice that there are three prongs and a mounting bracket that holds them straight. You will need all of this. However, at this point you need to take it apart completely.
Basically, each prong on the plug has a little notch on the bottom so that it can catch onto something and hold itself in place. So, the goal here is to cut out the holes so that when each of the three prongs are slid into place and the bracket put back on, they will all line up straight. This will take some trial and error.
For measurements I have included an approximate layout I quickly mocked up in Photoshop (unfortunately the file I was laser cutting from is no more). You are going to want to measure your plug for yourself.
Once all of the holes are cut and all three prongs are latched onto the lucite frame, you're then going to want to slide back on the yellow bracket that holds all three prongs in place. Please note that I cut a circle in the middle of the board. This is so that the bracket can press flush against the board (because the bracket has a little round protrusion in the back).
Once both plugs are in place and seem to line up straight, you are then going to want to see if they will fit into an actual socket.
DO NOT PLUG THEM INTO A LIVE SOCKET!
You should have an unused wall socket that is not connected to anything.
PLUG THEM INTO THAT! (as shown in the picture)
If, as shown in the picture below, the mount fits into the socket and lays flush to it, then you are good to go ahead to the next step. If not, break out your Dremel and keep at it until it does.
Step 3: Prepare the socket.
Alright, you have the plugs done and now you have to prepare the socket. This is easy. Basically, you connect the thick stranded wire on both sides and ground by screwing them flush with the metal plate. Screw in any screw you are not using.
Wrap the exposed connections with electrical tape to insulate them and make this device slightly safer. Do not wrap the tape around the screws used for mounting the socket. You may need them.
Step 4: Connecting the plugs and the socket.
If you have not figured out by now what is happening, let me explain it a bit. Basically, you are making a device that plugs over a live outdoor power box. This device for all intents and purposes looks exactly like the power box you are plugging it into, except it will be slightly bigger so that it can cover up the initial box.
MOST IMPORTANTLY, this new device will ALSO be powering a low-voltage DC device. Basically, one of the plugs connects to both terminals on the new socket and the other plug will run off to a cell phone charger (which is basically a really compact transformer).
So, the first thing you are going to want to do is cover the backside of the plug bracket with electrical tape in order to insulate it. Then, line up the bracket on the back side of the socket and use the plastic pull tie to hold it in place. That way, if you were to plug it into a socket just then (DONT!) it would be powering both plugs, but at the same time look as though a socket were facing you (see pictures).
There should be three wires running off of the socket. Connect all the wires to one of the plugs as follows:
1. The wire on the left side connects to the left prong
2. The wire on the right side connects to the right prong
3. The ground wire connects to the bottom prong
It should look like the picture. Once the two parts are tied together you can then attach the outdoor plate. After this it should look kind of cool.
Step 5: Break the cell phone plug.
First start by breaking it at the bracket that mounts with the cell phone. What do you see? If you see a red and black wire (or in my case red and brown) then you are in business. You should probably double-check to make sure that the red is plus and that the black is ground with a multi-meter or LED.
Once you have established that there are simply two wires under the black covering, cut it so that you only have about 6" of wire left. Strip off the ends of each wire. These are your low-voltage DC connections. They will connect to ANY low-voltage DC circuit that you want to attach to them.
The next step is to prepare the transformer (the large block part) to connect to the unused plug on your bracket. This is easy. Take your pliers and fold each prong sticking out of the transformer back and forth until each prong snaps off.
Now you should have two terminals flush to the transformer. Solder two thick stranded wires that are 4" long and stripped on both ends to each of the terminals. Wrap the transformer box in electrical tape.
Step 6: Connect the modified cell phone plug to the device.
This step is easy. There should be two stranded wires running off of the cell phone plug. Look at them. Now, find the unused wall plug on the thing that you are making. Connect one wire from the cell phone plug to one prong of the wall plug and connect the other wire to the other prong.
For now, tape the cell phone transformer to the side of the thing that you are making.
If you were to plug this device into a socket right now, you should have two fully functional wall sockets and a wire dropping down from the modified cell phone plug that should be 5V at 500ma capable of powering an LED (or whatever your device is rated at). I hooked my 5V to some bling. Hook yours up to your own bling.
Check the pictures for verification.
Do not touch live wires or stick your fingers into the sockets. Even the low voltage wires, if they are over 500ma, should be avoided. You probably should not touch live wires at any rating if you are pregnant or have a heart condition. This is coming from someone who has been electrocuted many, many times.
Step 7: Build a casing.
You now have a device that will plug into a socket, function as a socket and, all the while, power whatever small device your heart desires. This device is clearly in desperate need of a case that will camouflage it out in the urban environment.
The case needs to be approximately an inch and a half longer than the power box you intend to cover. It should be large enough to fit over the junction box, but still allow the device inside to be able to plug all the way into the existing socket. As well, when it is plugged in, the case should be relatively flush to the wall. The face plate should be about half an inch longer in all directions to allow for room on the inside of the case to install your own circuitry.
Even with such slight increases, you should still have more than enough room to fit your circuit board inside. However, do not take my word for it. Make sure that you do before you go to plug it in.
Once the box is built, you are going to want to paint it the color of the box you intend to place it over. If it looks more or less the same, most people probably won't even notice the difference or care to check.
I have yet to construct a casing that I am pleased with. I did get this aluminum (see picture) in hopes that maybe once painted, it would look convincing. I have yet to construct it. However, I'm sure someone should be able to figure something out; be it modifying an existing case or constructing a new one. I would be happy to hear suggestions.
Step 8: Install!
Once it is done, you should probably install it. I was thinking that the best thing to do would be to coat the edge of the case with epoxy. You may think about coating the front of the initial junction box with epoxy also. That way it will never come off. Well, not really. But it will take some effort for someone to pull it off. Bring a screwdriver because you may need to pry off the weather covering on the socket that is attached to the building.
I wanted to use this to have a constant source of energy for powering a circuit that would take sensor readings from the environment and transmit them to the internet. I was also considering using it to power a massive work of what kids these days are calling "Electro-graf." Although, I'm not really sure how much of a load conductive paint can handle.
Basically, if you want something powered out on the street, this is a possible solution. However, I under no circumstance advocate the construction or use of one of these devices.
***Construct and use this device at your own risk.***