Safety guide
Read this before you build or power up anything. These are the non-negotiable basics that keep coilers alive, not a complete course. The deeper safety canon lives in the Canon section, and if in doubt, ask before you switch on.
Understand the danger
This can kill you, and the myths make it worse
Tesla coils produce tens to hundreds of thousands of volts. The old "it's only a few milliamps, it can't hurt you" line is dangerously wrong: a mains transformer, a charged capacitor bank or the RF energy in the secondary all carry currents that stop hearts and cook flesh. The danger is not just the pretty arc at the top. It's the power supply, the primary circuit and the capacitors, which are far more likely to kill you than the discharge you're watching.
Two things that kill quietly
High voltage across your chest (hand-to-hand) stops your heart, and a capacitor that's still charged after you switched off feels exactly like one that's safe until you touch it. Almost every serious coiling injury traces back to one of these two. Everything below exists to keep you away from them.
Before you power up, every time
Ground everything
Bond the metal cases of every transformer, motor, variac, control box and enclosure to a solid earth. Give your coil a proper RF ground (a dedicated ground rod is best) that is separate from the sensitive electronics. A floating metal object near a running coil becomes a shock hazard.
Fit bleeder resistors and keep a discharge tool ready
Wire a bleeder resistor (roughly 1–10 MΩ, rated for the voltage) across every high-voltage capacitor so it drains itself when powered down, but never trust it. Keep a grounded discharge stick/hook within reach and use it on every capacitor before you go anywhere near the primary side.
Set up the bench
Work on a dry, tidy, non-conductive surface. Remove rings, watches and metal jewellery. Know exactly where the mains cut-off is and keep it reachable without leaning over the coil. One clear path to kill the power can save your life.
The rules you never break
Discharge capacitors before you touch anything
Capacitors can hold a lethal charge for a long time after power-off. Always short each one to ground with your discharge tool, then confirm it's actually at zero with a meter before working. Treat every capacitor as charged until you have personally proven otherwise.
The one-hand rule
When anything might be live, keep one hand in your pocket or behind your back. That stops current from crossing your chest hand-to-hand, which is the path that kills. Never brace yourself against grounded metal while probing high voltage.
Never adjust a running coil
Tune, tap and tweak with the power OFF and the caps discharged, never while it's energised. Stay outside the reach of the discharge, and keep metal objects (and yourself) away from anything the secondary could arc to.
Never work alone
Always have someone nearby who knows how to cut the power and start CPR. A high-voltage accident can knock you out or stop your heart instantly. You may not be able to help yourself.
The less obvious hazards
RF burns
The high-frequency energy in the secondary causes deep RF burns that can be surprisingly painless at first, then serious. Don't let arcs terminate on your body, give the coil a defined breakout point or strike rail, and never use yourself as the path to ground.
Spectators, ozone and UV
Keep everyone behind a defined perimeter, well outside strike range. Running coils produce ozone and ultraviolet light. Ventilate the space, don't run them for long in a closed room, and don't stare into big arcs.
Pacemakers and implants
The strong RF and magnetic fields around a running coil can interfere with pacemakers, defibrillators and other implants. Anyone with an implant must stay well clear. No exceptions, and make sure spectators know.
Fire and hearing
Arcs ignite dust, solvents and anything flammable. Keep a suitable extinguisher within reach and the area clear. Big DRSSTCs are also genuinely loud; protect your hearing.
If something goes wrong
If someone is shocked: power first
Cut the power before you touch them. If you grab someone who is still in contact with a live circuit, it takes you down too. Once it's safe, call emergency services and be ready to give CPR. A high-voltage shock can stop the heart even when the burn looks minor, so get medical help even if the person seems fine.
This guide is a starting point written for the community, not a substitute for hands-on training or professional advice, and it is reviewed by experienced builders. If you spot something wrong or missing, flag it. See the community rules and terms of service. When in doubt, don't switch on. Ask in Beginners first.