Safety Box for High Voltage Projects




Introduction: 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.

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 3: Get Ready to Cut

Mark out where you will cut to place all the parts (Ignore that mine looks like a face)

Step 4: Cut All the Pieces Out

Step 5: Sand the Edges and Drill the Holes

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.


Screw in all the parts and components!

Step 7: Wire Everything Togerther

Just in case you cannot read circuit diagrams:

One wire from the power cord goes to the switch, the other part of the switch goes to the button, which goes to one side of both outlets, the other side of both outlets goes to the fuse/circuit breaker which then returns to other wire in the power cord. The GREEN wire from the power cord goes to the green screw on the outlets, it doesn't go anywhere else.

In the photos I have attached both the fuse and circuit breaker in parallel, so don't let that confuse you if you only use one.

Step 8: You're Done!

Now you can gloat over anyone who does not have an awesome and practical Safety Box.



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    50 Discussions

    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.

    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.

    4 replies

    Reply 6 months ago

    I agree, but he's got a point. Just like he said below.

    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.

    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.

    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).

    as others have stated...this really needs an isolation transformer to be safe. 120 in 120 out but the diff is to get shocked you need to grab both wires and complete the loop not just 1 like you would from the wall.

    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.

    1 reply

    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.

    would be nice if this could take 220vac (usa) as well.

    an isolation transformer with an indicator led would also be nice for added safety.

    I suggest swapping one of the regular outlets with a GFCI outlet. The builder of this box will increase user safety greatly.

    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

    2 replies

    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!

    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?

    2 replies

    so you do not have to run back in the house after you extinguish the fire, and reset the breaker silly billy!

    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.

    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

    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