Safety Precautions Assembling Nixie Clocks with High Voltages

Question

Ricco

Hey guys, I’m assembling a nixie clock according to common instructions and at this point, I need to test high voltage components. The power supply is 12 V 250 mA, up to 170 volts. As far as I know, it’s potentially lethal. I don’t know what are the chances of dying from this. Can I accidentally kill myself when working with nixie clocks?

I’ve studied electronics in high school but I’m not an electrician so I don’t know what precautions I should take. What if I put on dishwashing rubber gloves?

• J1mmyD
  That’s a good question. Many people work with HV but don’t know anything about the risks. You are aware of the danger, and this is the main thing for safety.

Answers

Russel MacCullagh

This supply can kill you. I’ve had a few shocks at that level, and it was really bad but I’m still alive. However, there are people who can die, especially if they have any heart issues. Even if your heart is ok, I recommend that you never try to find out whether it can kill you. I’ve had 230 VAC mains shocks and one 1000 VDC, and they caused some nasty long-term consequences. 230 VAC is, probably, the worst experience.

A DC supply clamps your muscles, and it feels very bad.

I don’t think you should worry about HV, but you shouldn’t ignore it either. You may receive dozens of shocks one after another from such systems and they won’t hurt you. Or you can die as well.

Common advice is to keep one hand in a pocket when testing. This way, you won’t be able to close a hand to hand circuit via your chest. I suggest that you think twice before taking any actions, anyway.

Rubber dishwashing gloves offer a certain level of protection but only if they are not punctured and completely dry. They will, probably, protect you but I suggest that you consider them an added safety feature and act as if you were not wearing them.

When I work with live conductors, I keep my fingers curled inwards to eliminate grasping a live conductor if current triggers a hand clench. If you brush the back of your hand against an HV conductor, it will cause a muscle contraction towards your body but don’t rely on this.

The best solution is to turn HV off unless you need to test it. Think of what you’re going to do and make sure that you have all the necessary tools in place. It’s better to attach a meter with a test clip when power is off. If a test clip is not attached to the HV target properly, try to solder a wire to HV and connect it to the meter probe. But make sure power is off. When you have enough experience you may carelessly measure 500 VDC or 230 VAC mains with two probes when power is on, but don’t try to do it if you’re not experienced enough (otherwise, you may never get any experience). It’s usually safe, but not for beginners.

The main rule is MAKE SURE POWER IS OFF.

Quite often, power is on when people think that it’s off. I’ve seen such accidents so now I’m really obsessive about checking and re-checking. If you have to deal with a mains cord, pull out the plug, and make sure it’s the right cord. That’s what I do all the time. I know it’s obsessive, but at least, I’m alive.

Yesterday, I’ve installed a stove in my friend’s place, and there was only a wall mains switch between mains and me. It’s somewhat safe but potentially lethal. I tested everything with a meter and shorted all leads together to make sure mains are off.

Be careful and think twice before you do anything.

• Ricco
  Thanks for the good advice! Another question: why should I have the HV off until testing? This is what I have now. I don’t have anything plugged into the 5V, GND, and HV holes and I’m going to use a multimeter needle on the HV and GND with both hands. Should I plug some wire into the board and attach the multimeter to the other end with alligator clips? I’ve never done it before so I want to make sure I’m doing everything right. Thank you!
• Russel MacCullagh
  Potentially lethal tracks and components connected to HV are more extensive than the single point. Check my detailed answer to figure out powering and re-connections. Experience is crucial, so your task is, basically, to live long enough to become experienced 🙂
• J1mmyD
  It’s also worth mentioning that you can charge capacitors to a high voltage when disconnected from mains. Try to discharge large capacitors and then measure the voltage across them.