Electronics > Beginners
Hobbyist safety advise when working with AC
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Shock:
Read this whole chapter until you understand all the concepts.
https://www.allaboutcircuits.com/textbook/direct-current/chpt-3/importance-electrical-safety/


--- Quote from: gkmaia on February 05, 2019, 08:08:00 am ---Also how effective is an RCD in case my scope ground wire accidentally touches a live part of the circuit I am testing?

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Draw the circuit out (best way to learn). You want all your test equipment on RCDs even an isolation transformer if you have one. The RCD will definitely not save you in all situations but can help with equipment failure or if you accidentally trip it you can hopefully limit the damage to you and your equipment.


--- Quote ---One option would be to buy a differential probe but that is quite expensive. The other could be an isolation transformer to isolate the equipment I am testing. Could you comment on pros and cons of both options?
Would this be an option?

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Battery power oscilloscope with appropriate rating and isolated insulated inputs (handy).
High voltage active differential oscilloscope probe (bandwidth limited to probe, isolates and lowers voltage to the oscilloscope input).
Isolation transformer (doesn't isolate high voltage from the oscilloscope probe/input, isolates DUT from mains*)
High voltage probe (allows you to measure high voltages i.e. 40kV with the appropriate probe, can be very limited bandwidth)

Note: They all require you know what you are doing but with an isolation transformer you can easily undo any perceived safety by attaching additional equipment (one of many ways in fact). You should not rely on any device to keep you safe it's more about knowledge and a systematic approach to safety.

The link you posted is an auto transformer, it has no isolation. Isolation transformers have various different wiring schemes. I've not seen a suitable purpose built isolation transformer for sale here in Australia. We refer to ours as a bench safety isolation transformer or a technicians isolation transformer, ours are wired with the intended purpose of providing a fully floating mains source. A medical grade (or quality) isolation transformer may have additional safety features. But never assume anything is quality or is ever wired correctly because they often aren't.

I'll add a tip to those provided, always know the circuit you are probing and where the different voltages are, you can easily exceed your equipments input and less likely to learn what a Cockcroft–Walton ladder is the hard way.
Mechatrommer:

--- Quote from: gkmaia on February 05, 2019, 08:08:00 am ---But I do use a battery powered scope or mutimeter when poking these live things.

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the chance you get electric shock is higher when there is exposed gnd on the unit and you touch that while gnd clip connected to circuit. with bench scope, the gnd clip will be connected to earth and if you connect that wrongly, RCD will trip.

"fool" proof precaution:
1) wear insulating gloves
2) wear insulating boot
3) as mentioned RCD/GFCI/ELCB
"fool" means you can be a fool and still live.

also as food for thought, when you get a shock, your muscles tend to contract meaning your joints will tend to close down or elbow and shoulder to pull up. so when working with mains, if you see naked wire crossing or entering those "shock" or "reflex" path, you should stop and tidy up, its means you are working in a mess condition. for example if you get a shock your hand will grasp or fist, if there is naked wire in the middle, you will unintentionally grab that and you are in deep sheet, even if your other hand safe in one pocket. maybe its not very clear until the best guru ie the shock itself comes to you, it will make you sit and think for a while what was happening and how to avoid that in the future. but remember the "fool" proof hint above, esp the RCD/GFCI/ELCB thing, do not underestimate that, i think it saved me few times while working in a "mess" conditions.
MadScientist:
 An the OP give us a bit more on the specifics AC safety is a huge topic and really we need to scope out what you intend to do
vk6zgo:

--- Quote from: rstofer on February 05, 2019, 03:04:27 am ---Here is a publication by our state's safety enforcement agency:
https://www.dir.ca.gov/dosh/dosh_publications/Electrical_Safety.pdf

There are links to other documents like the formal regulations imposed on industry to help protect their employees.

Note that you will find rules regarding Personal Protective Equipment like gloves, flameproof attire and safety shield - depending on voltage level.

I think you might want to work downstream of a Ground Fault Circuit Interrupter (or local equivalent) and stay away from electrical distribution equipment altogether.

There's a lot involved in staying alive in the electrical business but the biggest factor in getting to retirement is LOTO - Lock Out, Tag Out and the associated testing techniques for proving a circuit is deenergized.

I think you need a better training program than arbitrary YouTube videos...

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A hobbyist is most unlikely to mess with electrical distribution equipment in Australia.
It is illegal, for one thing.

Even playing with Mains electric wiring inside equipment is a bit in the "nudge, nudge, wink, wink" category.
It is still technically forbidden, but so many hobbyists do it, the authorities pretty much turn a blind eye.
james_s:
How could they possibly stop someone? It's certainly common practice in most parts of the world for people to do things like replace the a plug or lampholder on a table lamp. Simple electrical repairs like replacing a switch, receptacle or light fixture are also very common DIY projects. Well within the abilities of typical homeowner provided they take the time to read the instructions. We're not talking replacement of the service panel or major remodeling.
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