Instructables

Safety box for high voltage projects

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Picture of Safety box for high voltage projects
This box acts as a third party between the outlet in your wall and whatever high voltage or dangerous project you are doing. For electricity to be flowing to your project from the box you need to be holding down a button, which serves the double purpose of making sure you know when you project is only, so you don't absentmindedly leave it running, and keeping one hand away from any high voltage so it cannot pass through you. WARNING: This box will not protect you from electrical shock, it will only make sure your project is running only when you want it to. NEVER have the box open while it is plugged in.
 
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Step 1: The parts

What you will need:
A container
A normally off button (Rated for at least 120v 15 amps)
A Switch (Rated for at least 120v 15 amps)
As many outlets as you want
A power cord
Wire (Rated for at least 120v 15 amps)
Things to hold everything together (screws, bolts, etc...)
E-tape (optional)
A fuse rated around 120v 15 amps
   Or you could use a circuit breaker rated for as much as you want it to trip as so you don't trip one on the main grid 

Step 2: Tools

Step 5: Sand the edges and drill the holes

Picture of Sand the edges and drill the holes
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Drill all the holes for the components you will attach.

If you happen to have sandpaper you can sand down the edges of all the holes to make it nicer looking.
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lovely211 months ago
I'm glad you thinking about safety. The first thing about electricity is you can not see it, often i'm working on a switch board and i'll see an exposed terminal, it looks perfectly ordinary however death is just one touch away.

For working on single phase applications, I suggest you look at a RCD protected outlet or purchasing a ISOLATION transformer.

RCD determine if any current is flowing threw the active and not returning via the neutral, the that current might be going threw you and thus it trips (breaks the circuit).

Isolation Transformers work by dereferencing the neutral from earth and thus there isn't a return path threw you. (Active -> Isolation Transformer -> You) vs (Active -> You -> Earth -> Netural)



In both cases, you should always remember this simple moto. "One hand in my pocket and one hand in the light socket", because if you ever get between the active and the neutral no safety device will protect you. Never lean over live electronics, never lean against or prop your self up on something especially something metal. Always wear shoes, a rubber mat is a good idea, if practical.
tutdude989 months ago
i live in Europe and here we have 240v so do i need to use 240v 5x20mm fuse (like one in multimeter) ? what amperage will 1 amp work ( for 240w ?) for my soldering iron or glue gun etc.
Mechanicalanimator (author)  tutdude989 months ago
From what I have found, the wall sockets in Europe produce 240v at around 16 amps, so thats where you would want your fuse or circuit breaker to be at, but I am sure there is someone who knows the specific amps for your sockets, so feel free to comment if you have something to add on.
baecker0310 months ago
would be nice if this could take 220vac (usa) as well.
baecker0310 months ago
an isolation transformer with an indicator led would also be nice for added safety.
brgt4011 months ago
I suggest swapping one of the regular outlets with a GFCI outlet. The builder of this box will increase user safety greatly.
robotmaker11 months ago
the microswitch you are using is rated at 1 amp,and the circuit is rated at 15 amps that will not handle the current rating of your design
Mechanicalanimator (author)  robotmaker11 months ago
No, it is rated for 15amp and 120v, which is why I chose to use it.
The box should be a approved metal or plastic electrical box, not a tupperware. And the box is still hot even when it is off, therefore, making it very unsafe. I would NOT use this!
soundgod0611 months ago
Fuse and circuit breaker in parallel? Why? That arrangement would require both to trip to shut off power. Series would be the better choice if you really want both, but again why would you want both?
so you do not have to run back in the house after you extinguish the fire, and reset the breaker silly billy!
Mechanicalanimator (author)  soundgod0611 months ago
I was either going to take a out the fuse or turn off the switch depending on when I wanted it to shut off, because they were rated for drastically different levels.
spark master11 months ago
err glorified extension cord?


I would make it out of a "deep" 5 inch square box, in metal, ground the box and the receptacles remove 1 duplex and mount switch there .

You need to buy the appropriate cover plate for receptacle and switch you can even put an idiot light on it by using a switch with a neon inside it.

then its all steel grounded and has some gfi protection. You can buy reducers so you can have switches
uncle frogy11 months ago
I built a disconnect switch in a handy box with a single throw switch and a double pole switch to disconnect hot and neutral simpler and quicker than pulling the plug. I also built In a large gang box a large 12A RFI, w/fuse , surge suppression and switch I can use in the field.
I had not thought of a deadman switch before great idea, I will upgrade to 20A and maybe a pilot light or two.
great idea
uncle frogy
kminer49er11 months ago
Here are a couple of phrases that I use to teach others where to connect the 3 wires when hooking up a 120 volt AC device: "Long John Silver was a white guy." 'Long' references the long receptacle slot; 'Silver' references the color of the terminal screw; 'White' references the color of the insulation on the wire. If you get that part right what's left is the wire with the black insulation and the ground wire "Green grass grows out of bare ground." The ground wire has ‘Green’ colored insulation or is bare (without insulation) and is connected to the (usually) green terminal screw. That's two out of three leaving: “A black widow spider with the short gold teeth is deadly.”
Uisge11 months ago
I like the idea of this project, but the way you have built it is DANGEROUS.

As mentioned below, you have the the black and white wires reversed, this means that whatever is plugged in will always have 120 volts applied, with respect to ground. Also, you did not wire it according to your diagram.

The wiring should follow this path:

BLACK WIRE: enters box, goes to fuse, from fuse to (optional) breaker, from breaker to on/off switch, from on/off switch to temporary switch, from temporary switch to BRASS screws of receptacles (narrow slots of receptacle). This is very important, and the first way to ensure you won't be electrocuted.

WHITE WIRE: enters box, goes to SILVER screws of receptacles. That's all for the white wire; it should never be switched.

GREEN WIRE: enters box, goes to green screw of receptacles, and on/off switch.

WIRING: Since you're protecting this at 15 Amps, all your wiring should be 14 AWG; nothing smaller. It would be preferable to use solid, instead of stranded.

CONTAINER: This would not pass any safety inspection, and I would suggest you get an approved plastic or metal box.

FUSE and TEMPORARY SWITCH: you've wired these in parallel, meaning that the fuse will always bypass the switch, leaving your receptacles live at all times.

FUSE HOLDER: Please get a proper fuse holder with screw terminals, so that you have a proper mechanical connection for the wires, and are not holding them together with solder. This is an important rule in proper electrical connections.

WIRE CONNECTIONS: Please use wire nuts, or Marrettes (brand name). These give proper mechanical and electrical connection and protection. Yes you can tape the wire nuts after, but the connection should be done with the wire nut first.

As said at the beginning, I like the idea, but unfortunately this project is really DANGEROUS the way it's been built, and I really don't want to see anyone get hurt by using this, thinking they are being properly protected; because they aren't protected by this.
Wazzupdoc Uisge11 months ago
I agree. This should all be put into a proper electrical box. If ground-fault outlets are used (some come with switches ) there is no need for a fuse or a breaker. Any accidental grounding ( including the user) will immediately trip the outlets and prevent electrocution. Also, any outlet daisy-chained from the GFCI (including 3-wire extension cords) will be protected in the same way.
NB: In spite of seeming simplicity of circuits such as this, ignorance of electrical practice makes any simple project potentially lethal. I suggest going to your local home improvement center and getting a book on basic wiring technique. It's cheap life insurance.
Mechanicalanimator (author)  Uisge11 months ago
Even though though this is not ideal safety wise, and the box would not pass a safety inspection, it is much safer than plugging a high voltage or amperage project directly into a wall with no control over it besides pulling out the plug, which as a few people pointed out, is difficult if you have just been electrocuted.
JettaKnight Uisge11 months ago
Since this is probably the most coherent response, I'll comment on it and the original design.

The wiring in the box doesn't seem to match the schematic. The fuse is bypassed, neutral and line reversed, etc.

The box is decent enough for the application (hobby work).

Consider using a GFCI outlet (to protect you!) and a switch that disconnects both line and neutral (double pole).
Uisge11 months ago
Mechanicalanimator, you've made some great improvements to the project. Good work. I now don't consider it to be dangerous.

There is still a couple of issues that i think should be addressed:

WIRING ORDER: Your diagram shows that the black (live) wire goes to the fuse/breaker first, and then the switches. When you built this version of the safety box, you connected to the switches first and then the breaker. Putting the breaker first shuts off all power to the rest of the components when it trips. I suggest you change it to match the diagram.

DIAGRAM: The diagram shows the hot live wire going to the wide slot. It should go to the narrow slot (I remember it by: the narrow slot is harder to stick something in, so it should be use for the live wire). It looks like you actually built it properly, but the diagram doesn't reflect this.

JOINTS: You can actually eliminate the joints all together by 'daisy-chaining' your connections. For example:
- White wire: Connect the white wire to the first receptacle, and first silver screw. Then connect a jumper wire from the second silver screw to one of the silver screws on the second receptacle.
- Black wire: Connect the black wire as in your diagram: Breaker, then switches, then go to the first receptacle, first brass screw. From the second brass screw, connect a jumper wire to the second receptacle brass screw.
Joints eliminated!

If you make those changes I suggested, I'll vote for this project.
Mechanicalanimator (author)  Uisge11 months ago
It is difficult to see in the picture, but the live wire does go strait to the breaker, I'll upload another picture when I fix the diagram. Thanks for pointing out my mistake there.

I originally planned on daisy chaing the outlets, butfue to my severe lack of foresight I cannot get a screwdriver in at a good enough angle to loosen the screws to switch the wire. I had to improvise and connect those wires beforehand, and attach them to the rest of the circuit later (the other wires would not reach them when they where out if position).
mstanavech11 months ago
Ummmm nice box but you're switching the neutral side. There will always be voltage present in the outlet.
Mechanicalanimator (author)  mstanavech11 months ago
I'm glad you have your beliefs, but it works perfectly fine, thanks
gbauer11 months ago
Good job, but this is a low voltage safety box, and definitely unsuited for high voltages...

In electric power transmission engineering, high voltage is usually considered any voltage over approximately 35,000 volts. This is a classification based on the design of apparatus and insulation.

The International Electrotechnical Commission and its national counterparts (IET, IEEE, VDE, etc.) define high voltage as above 1000 V for alternating current, and at least 1500 V for direct current—and distinguish it from low voltage (50–1000 V AC or 120–1500 V DC) and extra-low voltage (<50 V AC or <120 V DC) circuits. This is in the context of building wiring and the safety of electrical apparatus.

In the United States 2005 National Electrical Code (NEC), high voltage is any voltage over 600 V (article 490.2). British Standard BS 7671:2008 defines high voltage as any voltage difference between conductors that is higher than 1000 V AC or 1500 V ripple-free DC, or any voltage difference between a conductor and Earth that is higher than 600 V AC or 900 V ripple-free DC.
Mechanicalanimator (author)  gbauer11 months ago
The high voltages I mentioned would be produced after the box, by whatever device the person happens to be using, this is simply a step between the wall and your project, for example, the 15Kv transformer that I am using in my projects.
gn0stik gbauer11 months ago
This is basically just a dead man switch between him and his HV project. Yes it is still low v at this point. The transformers that turn it into HV are typically going to be part of the project he's working on, like a tesla coil, or Jacob's ladder, etc. This prevents the low v house current from supplying your project in the event that you get bit.
Mechanicalanimator (author) 11 months ago
Thank all of you for pointing out my wiring mistakes, which I have done my best to rectify.
AJMansfield11 months ago
The other main problem here, too, is that in a good design, both the fuse, breaker, and main switch should be on the hot side. This answer on EE StackExchange discusses why that is.  From the answer:
"As suggested by rawbrawb, a footnote on why low-side fusing is avoided in higher voltage designs, i.e. where the supply voltage is either DC, or AC at mains voltage or sufficiently high voltage such as to be harmful or painful to accidental touch:

"The ground return is also the "no voltage" or safety return path for a circuit, essentially zero Volts, safe to touch, and in circuits with a non-isolated power supply, often connected to the device chassis and eventually to building earth.

"A natural perception in a non-operational device is that other than the supply line itself, the rest of the circuit should be safe to touch. When such a device is fused on the return path, the rest of the circuit will rise to the supply voltage, in other words will be "live" or electrically "hot" when the fuse blows, since there is now no return path. Touching such "hot" portions of the circuit (pretty much all of the circuit) would then make the human being the return path for the supply voltage.

"Until humans get bioenhancements which incorporate internal fuses, this exposes users to potential risk of electrocution or injury during device diagnosis, from what should have been a "dead" circuit. Hence, in high voltage devices, having the fuse on the high side is pretty much mandatory. Yes, additional fuses for individual sub-circuits might be used as well, for the low voltage sections for instance."

The moral of the story: do it right so you don't get zapped.
ndjalva11 months ago
Where's the GFI?
Liam.great9811 months ago
What I find happens to electrical tape over time, is it dries up and gets crispy. However it also becomes permanently sealed onto any part that is stuck to itself, like your electrical tape immitation marrettes. So technically, it isn't safe and should be replaced, but practically, I wouldn't worry about it...
ktbman11 months ago
nice i definately want to try this idea!
tiggeroush211 months ago
Nice job. As far as the tape goes, don't worry about it. Some Electrical inspectors still require people to use tape. We had one inspector require us to tape all of our wire nuts.
Just remember Black on brass and white on silver which is to say power on brass screw and neutral on silver screw. All fused, breaker, and switches go on the hot wire. I used to work in the factory that made those outlets till it was closed. Keep up the good work.
bremus tiggeroush211 months ago
Look again. There is no wire nut, just tape.
tiggeroush2 bremus11 months ago
I know, I was not stating you used wire nuts, but directed more to another post saying you should use nuts and not tape.
bremus11 months ago
I don't know about putting 110v in a Tupperware box.
robotmaker bremus11 months ago
needs to be a grounded box live approved plastic or metal enclosure
robotmaker11 months ago
circuit tester is always a good way to check if the wires are reversed and like UISEGE said it reverse and dangerous
still a great project the switch idea is called a dead man switch,i design many for in-house testers for a electrical company i work for ,

second another good safety design is a light blub in line with the hot or across the
power switch if the light is dim circuit it good if very bright your circuit under test is bad

plus current is low so almost no shock


gman2000watts11 months ago
Nice but a bit too much work. as all the electricians posted, the tape is a no go! But why not just use a gfci? It has a built in circuit breaker so it trips when overloaded and when water is spilled over it.
RichardNeill11 months ago
Please don't use electrical tape! It's really dangerous stuff, because over the course of time, the adhesive dries out, and it will come off!

Also, if you want to make it really clear that your project is live, why not add a red light inside your box.

Bratster11 months ago
WARNING, it appears you have the hot (black) wire hooked to the neutral side of the outlet. and the neutral (white) wire hooked to the fuses and switches then to the hot side of the outlets. This is incredibility unsafe. with respect to ground (green) the hot has 120V and neutral has 0V.

the way you have it wired, there will always be 120v on the neutral (0V) side of the outlets.

breakers, fuses and switches should always be on the hot (120V) wire and NEVER the neutral.

not only is the 120v not being switched off, it is on the wrong side of the outlet.

on standard outlets the gold screw is hot (120V) and the silver screw is neutral (0V). green is ground.
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