High Voltage and General Safety

For the skilled coil builder, you either already know or have found out for yourself how dangerous the voltages can be. Having worked in the electrical industry for over 30 years, i've had my share of shocks, I used to deal with 240 and 415 volts on a daily basis, Getting a shock from 240 just throws you back in my experience, and you may get a small burn unless you have a weak heart, or the current gets high enough. Generally 240 volts will find a path from entry point to exit point, and you'll know if it's damaged something.

The voltages and frequencies used in many of the Tesla coils can cause 'invisible' damage, from reading the notes on building coils, you'll know that the voltages travel on the surface of wires, this is also the case with the body, If a spark goes from entry to exit, it will follow the surface of whatever it comes into contact with.

You may think it's clever to be able to hold your finger on a high frequency spark, and only feel a little bit of heat at the point of contact, but what is it doing on the surface from entry to exit ? Think before you show off.

IMPORTANT: even though you know everything about safety, others may not, so make sure they keep their distance, define a safe zone, and enforce it rigorously. Do not build coils or other high voltage devices for other people unless they are fully aware of the risks involved, and can demonstrate safe use.

Maybe the appropriate sign should be something like this


As with any electrical apparatus, a good earth is essential for any exposed metal parts. In Tesla coils there should be 2 earths, one for the mains powered equipment, and one for the RF system. Mains powered equipment should have any metal case bonded to the normal electrical system in the house, mostly this would be via the normal electrical outlet, you may need to use an outlet without a 'Ground Fault Interrupter' (GFI).

The RF earth should be a rod driven into the ground, and should be away from any normal house earthing rod, a simple rod could be a piece of copper tubing, but you may need to make a hole with something more substantial first, you can pick up a proper earthing rod from an electrical supplier if you prefer, they can take the hammering into the ground. The RF earth would ONLY be connected to the secondary coil at the base, Spark rail, earthing wand (if used) and any associated RF point, it should not be cross connected to mains earth as this could prevent any earthing safety device in the home from operating normally.

In my set up I have a point on the wall that I can plug into as needed for the RF earth, And for added safety I have a stand with a crossbar for the sparks to ground themselves before they can reach other electrical items in the room, think of it as another spark rail.


Well we all need it to power our devices, and it's all too easy to lash up something with a bit of wire from the scrap box, but be warned.
Many cables that are rated for lower voltages look similar to those used for mains, Yes a telephone wire will power a 100watt mains lamp, but the insulation is not rated for mains use. When powering your devices from the mains, you've probably done the calculations for resonance etc, so do the calculations for the expected maximum power of the equipment, then be sure to include a fuse of the correct rating.
Also make sure that wherever you power the equipment from, that you can easily turn it off without risking being too close to any of the high voltages of your device. Make sure that any helper knows this too, One guy I read about has a 'knock off' or 'dead mans handle' that only needs the use of a piece of string to turn off ALL power, this is a simple but effective idea, make sure you do a safe test on this. And don't forget to ensure you have the correct fuse rating installed to protect the equipment and yourself.

Power tools and hand tools

Coil builders will want to use a few tools to make their creations, Please read all documentation that comes with any power tool for safety, in the manual it will state that you should be sure all guards are in place when in use, I know from experience especially with DIY style power saws that this is not always convenient, especially when making grooves.
All I can say is that you should be aware of what you are doing, a piece of wood dropped on a bare spinning blade can shoot it across large rooms, so it can be assumed that it will hurt if it hits you. When cutting wood with a power saw, stand to one side in case it jams and tries to fly back

Never leave power tools running more than is needed, you only have to lose balance and put your hand on the blade when you stop yourself falling. Be sure any helpers know YOUR rules on safety, don't assume they know how to be safe with your equipment.

Make sure you have no loose clothing or long hair that is able to make contact with rotating machinery, loose clothing can drag your hand into the blade in fractions of a second

Hand tools don't seem that dangerous, but one of the most common injuries amongst electricians is a stab wound to the part between finger and thumb, on that 'webbed' part, It's as a result of holding something in your hand while using a screwdiver and it slips.

Try to work so that any slip will be away from you, it's not uncommon to hear about woodworkers holding the far end of the wood while using a chisel, either get some clamps, or screw a bit of wood to the bench as a stop.

Adhesives, Varnishes and Solder fumes
Many adhesives and varnishes are chemically based, always read the information on the tin, you should have a well ventilated area and no naked flames. Solder has it's own problems, not just from the heat, but the flux fumes should be ventilated away, if you are doing close work, maybe set up a fan to suck the fumes away from your face.

General Housekeeping

No, this isn't about doing the housework, it's about keeping the workplace tidy. Not just the workshop while constructing your devices, but also where you test out the equipment. Keep a broom handy while constructing, if you find you're standing on offcuts, then have a sweep around, you don't want to be standing on that bit of wood or a pile of sawdust if you have to move in a hurry, you'll probably slip on it.
At the end of the day, clear away that pile of rubbish. Same goes for the test area, if there's bits and pieces lying around, you could trip onto your Tesla.

A little hint try working in bare feet for a day (as long as you are not likely to drop anything heavy on your foot), you'll soon find that you want to clear the floor more often.

Dust can be a major hazzard

Many coil builders use MDF, this stuff is not only dusty, but contains chemicals for bonding it to make a board, The dust is fine enough that it will hang in the air, and you could breathe it in, if it gets in your lungs, it could seriously clog them up, maybe get and wear a mask that's suitable for dusty conditions, and don't just throw the mask down after use, you don't want that dust on the inside for when you put it on again.

I see a lot of people will use the best mask available, and no extract system, they'll cut the material, and as soon as it's done will remove the mask, but the dust is still floating around, Please be aware of that dust.
When using power tools, you should get a shopvac, most power saws, sanders, routers etc have an adaptor for attaching a vac.
If you have a mini workshop with several tools, a powerful shopvac along with some plumbing wastepipe, flexible vaccuum cleaner hose, and connectors would mean you could have them all connected to a common extraction system,

For power tools that don't have a built in extractor adaptor you ca hold the hose near the cutting area.

For the techies, you can get a 'current operated relay', if you wire it up correctly, when you start a power tool, the vac starts automatically.

Obviously the shopvac can aslo be used for the clean up.

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