Safety Practices, General and Ultra-High Voltage

[barts]

We power engineers call anything up to 1000V as low voltage, but then we're a little fuddled by standing too close to HV transmission lines.

The best advice I received when starting out was to keep my hands in my pockets. Anyone who plans to spend any amount of time tooling with electricty would do well to read a book such as the Electrical Safety Handbook. Only sections of this would apply to the hobbyist however, perhaps some more learned members can suggest a more suited publication.

[promitheus]

Well working with high voltage is always dangerous.
What you should use is a isolation transformer on your workbench with ground fault automatic switch. This will save you from almost any electrocution at 200-500 Volts.

When it comes to extremely high voltages like 1000-2000 volts for instance when building SE Amplifiers with RF Amplifier tubes 833, 811 etc you should really know what you are doing. Ask the people who work with RF transmiting Tubes. The ARRL books, websites and info is a good start.

I have heard someone was killed from a radio transmiter when he had his screwdriver too close to the tube anode. Not touching but too close. The arc went through the air through the screw driver. VERY DANGEROUS.

[DrDeville]

Originally posted by barts
Anyone who plans to spend any amount of time tooling with electricty would do well to read a book such as the Electrical Safety Handbook. Only sections of this would apply to the hobbyist however, perhaps some more learned members can suggest a more suited publication.

Thanks Bart!

I checked the book out, and it looks very useful and seems to adress the sorts of questions I was wondering about, like arcing.

I plan to buy this book unless someone recommends something better. It would be great to find one specifically aimed at DIY eletronics, and would not only contain safe usage/test practices, but safe design considerations (e.g. how to avoid arcing).

This looks like a great start. Any other suggestions?

Best,

George Ferguson

[sam9]

Please add: Wear eye protection.

Even at low or modest voltages I have thrice had small components explode in my face (or close enough to make me jump). An LED, a TO-92 transistor and a cap. In each case I was wearing saftey glasses. None of these were life threatening but without the eye protection I could have lost an eye. All were due to mistakes on my part but the dumbest thing I think you can do is believe you will never make a mistake!

[Aud_Mot]

Before you do anything,

1) ASSUME that every piece of exposed metal is hot with a high voltage.

2) Act as if every bit of insulation is not truly insulated.

3) Unplug it.

4) Discharge all caps.

5) Work slowly.

6) Be aware of the spark and jerk reaction or the zing and jerk reaction. When you see a spark or get a tingle of voltage, you will jerk you hand to just about any direction. The pulling back can be dangerous and also damage your project.

[cyclotronguy]

We have not been talking about high freq, directly but it seems to be a subject we are nibbling on.

RF circuits can fool you, voltages are often induced into places you would never expect them to be. Under the right circumstances any piece of conducting material in the area can be hot. When you ground part of a high frequency circuit, it may or may not in fact actually be at ground potential. Combine HF or UHF with high voltage and a whole new set of rules apply.

Know those rules, know the circuit, double check your safety chain.... stay alive!

Cyclotronguy

[DrDeville]

Promitheus wrote:

The ARRL books, websites and info is a good start.

Thanks for the tip! I nosed around the site, and could not find anything online that has not been mentioned here. Please let us know if you know of anything online that we have not included already.

Thanks!

Oh, and stay out of the sun! (mythological joke there )

George Ferguson

[SY]

In that regard, a neat trick is to use a neon light bulb (like an NE-2) at the end of a long plastic rod (like a meter- use UHMW, not nylon) to probe for high voltage RF. This can save you from getting zapped from unexpected places even when using a supposedly-safe HV probe.

One side benefit of the NE-2 trick is that you can even estimate the frequency from the color of the bulb.

[richwalters]

If you are working on a HP'r switchmode power supply then eye protection is a must.....an exploding semi is basically a down sized handgrenade. A boost converter with all that low Z output capacitance plus a defective feeback loop is more lethal than any conventional tranny mains cap input powered DC system.

Ear protection.....whaz's that ? Been/am married....know all about that.....

rich

[DrDeville]

Eye protection--great tip. Thanks!

I also appreciate the tip on using an isolation transformer on the workbench.

Could someone explain how an isolation transformer is different from the common Ground Fault Interupt outlets now mandated for bathrooms, pools, and other wet/BareFeet areas?

If it did the same thing, a GFI outlet would be easy to find and install.

Thanks, and keep the tips coming!

Best,

George "Clueless" Ferguson