Do you guys use an isolation transformer for your lab/workbench?

[AVGresponding]

I couldn't find any seller that only sells one glove.

Bob has you covered:     www.bobthewelder.com.au/products/xt-left-handed-welding-gloves-green-long

---------------------

FWIW folks: 30ma RCDs rarely trip at 30ma

Anywhere from 15 to 28ma  is what usually happens, and a good unit will have about 2 to 3ma repeatability

i.e. test the suckers properly before trusting your life and gear with them,
better still, use two RCDs  piggy backed.
One of the two 'may' trip 'faster', or both will work if the trip current approaches zap city.

But they won't do you much good with an electrical fault or short in the chain, so..FUSE UP, just past the DUTs current rating,

and you won't need an imitation rabbits foot or garlic necklace 

Yes, unlike fuse or circuit breaker ratings, the RCD trip current is the maximum allowable for it to meet its standards.

This is a pretty good source of info on RCDs:  https://www.eaton.com/content/dam/eaton/products/electrical-circuit-protection/circuit-breakers/xeffect-rccb/eaton-rcd-application-guide-br019003en-en-us.pdf

[nightfire]

While we are getting into the topic of RCD:

a) They usually trip in between 0,5*rated diff. current and 1*rated diff.current. Usually manufacturers try to adjust the ti the middle of that range when they are new, so usually those RCD trip between 20-25mA for a 30 mA standard type.
b) When relying on RCD protection: Which waveforms do you expect? If it is not sine wave, the standard RCD type A would not do much...
German manufacturer Doepke has very good material there, called "Allstrom Fibel", downloadable as pdf. Also some general notes on RCD and stuff.
(www.doepke.de)

[themadhippy]

Out of curiosity do the rules for GFCI in the states stipulate a disconnection time,ive had a quick google but find conflicting advice,the only thing  that made sense was T = (20/I)1.43  , but this seems to give  longer times than permitted in the uk,so whilst ours have a higher current before operation it appears ours must operate  faster

[nightfire]

In germany, the corresponding standards mandate a maximum of 0.3s, the low voltage regulations ((up to 1000V) mandate 0.2s above 230V- in reality a fresh RCD in mains installation is tripping faster than 30ms- older models can take a bit longer, in some cases due to old grease in them. This is also the reason why those RCD should be actuated in regular intervals, to prevent grease hardening etc.

[wilhe_jo]

Just a thing to consider...

Even at some none budget suppliers website, a differential probe is at 200.-
I got my vintage Tektronix ones very well below this...
Migsig ones are below 100.-

Do you really want to risk touching life mains, or do you want to risk mains/Gnd short just because it always was like this?

I had quite a enlightening event with a client (10B/a revenue!) some years ago.
When I arrived, I was taken too seriously, because I got there with dated stuff.... Yeahh... Ok..I sell knowledge not decoration ...

Then they got their measurement rig up....

Probing with two brand new Lecroy HD Scopes and 2 isolation transformers (also fresh from the egg).... Perfect.

Effectively they had 2 usable channels per scope.
And using the touch screen is out on the intentional use....
Yeahh. That's the way I want to work!

They were frightened about frying the touch... So we had to shutdown power for every interaction with the scope....

Really, get diff-probes!

2x diff probes
1 current probe

That's what you want to have for single phase!

Just to be clear: my 3 phase dif-probes and my 3 phase current probes were around the price of the 2 premium iso-transformers.

Apart from this, a RCD protects you from things, somebody clever hasn't thought about (or is really, really, really unlikely).
Debating whether ab RCD is an appropriate safety measure to protect you from common mistakes is ... brave.

Work as if you were drunk!
Honestly. That's pretty much what happens in accidents due to laziness or distraction.

Diff-probes keeps the RCD on your side.
An Iso transformer makes the 10+A breaker your only friend!

Oh, yes I work with isolation transformers... A LISN needs that... But you can reduce the pain...

73

[nightfire]

I have some diff probes on my shopping list, but even micsig are 200+ Euros here in germany- do you have any hints where to buy used gear that is not worn down?

Regarding RCD: Yes, they are very useful, so they should be included in every setup on a work bench, but in case you really need then and they do the things they are intended to do, you also get zapped- at least a little bit.
Therefore I would regard them as one of the multiple pieces you (or the one setting up a bench) should consider as part of safety measures.

Which means, that the person doing the setup is responsible for this, and has to think beforehand if a safety/isolation transformer in front of the DUT will and can improve the safety, or simply be a cause of different issues.
In the same league I would sort:
- gloves
- isolated bench
- isolated tools
- diff probes
- lightbulb inrush current limiter
- RCDs (including type B for pulsed or DC currents)

[Electro Detective]

Whatever 'isolation' strategy used, don't forget protective eyewear, it's one - oops! arghhh!!! ****! -     you can't easily walk away from

How many times do people stick their face into a project or repair    filled with with pop-able capacitive parts and solder fumes etc


FWIW, there is NO way I would rely on one 'worked fine yesterday..' RCD or GFCI to bail me out of a situation involving voltage surfing

especially if not externally trip tested immediately beforehand rather than the onboard TEST switch

Have come across a few faulty mains switchboard units that tripped fine with the onboard TEST monthly 'good luck' switch,
that NO ONE on this Earth ever tests, remembers, or even knows about..

but same RCD big fail when pumped externally or at the domestic power point receptacle with 30ma and beyond. 


Another factor many may have not considered is using smaller, fast fuse input and delayed fuse output, isolation transformers,
that just meet the current draw requirements of the DUT
This way you at least are not copping the full output of the street transformer through the shorted gear or shorted YOU!

i.e. if most of the powered DUTs you work with only pull in under 1 amp, why have that 10 or 20 amp isolation transformer monster powering it,
unless there is DUT inrush surges to consider?

Plus the junior sized one hums and buzzes less, easy to move about and find parking space,
and may be all you can afford at this time.
or if you can afford or have both, bring out the big one when needed 


Either way any of the above may be 50/50 coin toss 'luck' unless you read up and understand 'isolation' in all it's forms and RCD/GFCI pros, cons etc


You only have to spend that time learning and testing ONCE, verifying what you think you now know safely, and get on with it,

or toss coins for the rest of your long (or cut short) electo-life using and surfing suspect voltages

Personally I'd rather swap out fuses, reset breakers and RCDs,
and work from a a tested working isolation transformer,
and avoid the local street power transformer  trying to supply all it's current into the gear or me   

[nightfire]

To alleviate the fear of grilled by the street transformer: It only can do 230V in case of a short circuit in the DUT. Voltage in case of a real low impedance short also tends to drop a little, so basically the most annoying part of it would be particles moving away from the DUT with high velocity and/or temperature.
 This is also limited a bit by the impedance of the cable from the DUT to mains, which limits the short circuit current a bit. Rule of thumb: After 3 meter of 1.5mm², there can be onyl around 2000A- in reality, a standard outlet brings between 200A and 400A short circuit current- here the type of fuse you use would be important, as those clear glass fuses can break under this stress. So ceramic fuses are strongly recommended if you want to protect against shorts like this.

Also a reasonable fuse limits the short circuit current a bit, so that part of the (prospective) energy goes into melting the metal inside of the fuse.

Depending on the isolation transformer, you can change the fuse, so exchanging the mostly slow-blow fuses to faster ones or with lower rated current is also a way of getting them a bit more sensitive.

[tautech]

Think what I might do is build a lamp socket with a bypass switch and mount it up on the wall and keep a few incandescent bulbs laying around for current limiting, 40w, 60w, 100w, 150w flood. Use that for powering DUTs when needed otherwise use the bypass switch normally.

Too complex, just KISS.

That was a similar plan to what I had with an always ON DBT through the bulb and flick the switch the other way to bypass the DBT and supply full power to the DUT.
I just used that ^ setup for a very short time then became properly aware of the hazzard it was and changed the switching to just a series power switch to properly kill the power and not the user !

That's not to say you can't build something lots lots safer with dual switches or a 3 position switch but unless you're using it all day IMHO it's better to KISS.
Below is the DBT I knocked together with scrap from around the bench all those years ago and it's remained unchanged since the mods to make it safer.

[nctnico]

I couldn't find any seller that only sells one glove.

Bob has you covered:     www.bobthewelder.com.au/products/xt-left-handed-welding-gloves-green-long

---------------------

FWIW folks: 30ma RCDs rarely trip at 30ma

Anywhere from 15 to 28ma  is what usually happens, and a good unit will have about 2 to 3ma repeatability

i.e. test the suckers properly before trusting your life and gear with them,
better still, use two RCDs  piggy backed.
One of the two 'may' trip 'faster', or both will work if the trip current approaches zap city.

But they won't do you much good with an electrical fault or short in the chain, so..FUSE UP, just past the DUTs current rating,

and you won't need an imitation rabbits foot or garlic necklace 

Yes, unlike fuse or circuit breaker ratings, the RCD trip current is the maximum allowable for it to meet its standards.

Did'nt read the Eaton article but fully I doubt this statement is entirely true. There has to be a minimum as well so you have a defined amount of allowed leakage current. Otherwise it wouldn't make sense to sell unsensitive (300mA) and super sensitive (5mA) GFIs / RCDs

[AVGresponding]

I couldn't find any seller that only sells one glove.

Bob has you covered:     www.bobthewelder.com.au/products/xt-left-handed-welding-gloves-green-long

---------------------

FWIW folks: 30ma RCDs rarely trip at 30ma

Anywhere from 15 to 28ma  is what usually happens, and a good unit will have about 2 to 3ma repeatability

i.e. test the suckers properly before trusting your life and gear with them,
better still, use two RCDs  piggy backed.
One of the two 'may' trip 'faster', or both will work if the trip current approaches zap city.

But they won't do you much good with an electrical fault or short in the chain, so..FUSE UP, just past the DUTs current rating,

and you won't need an imitation rabbits foot or garlic necklace 

Yes, unlike fuse or circuit breaker ratings, the RCD trip current is the maximum allowable for it to meet its standards.

Did'nt read the Eaton article but fully I doubt this statement is entirely true. There has to be a minimum as well so you have a defined amount of allowed leakage current. Otherwise it wouldn't make sense to sell unsensitive (300mA) and super sensitive (5mA) GFIs / RCDs

If you had bothered to read the article, you would have found out that the regulatory requirement is that the device should operate at between 50% and 100% of the rated trip current, and that typical trip values for a 30mA RCD are 18-23mA, with a 2-3mA variance in repeatability for good quality devices.

[Electro Detective]

I couldn't find any seller that only sells one glove.

Bob has you covered:     www.bobthewelder.com.au/products/xt-left-handed-welding-gloves-green-long

---------------------

FWIW folks: 30ma RCDs rarely trip at 30ma

Anywhere from 15 to 28ma  is what usually happens, and a good unit will have about 2 to 3ma repeatability

i.e. test the suckers properly before trusting your life and gear with them,
better still, use two RCDs  piggy backed.
One of the two 'may' trip 'faster', or both will work if the trip current approaches zap city.

But they won't do you much good with an electrical fault or short in the chain, so..FUSE UP, just past the DUTs current rating,

and you won't need an imitation rabbits foot or garlic necklace 

Yes, unlike fuse or circuit breaker ratings, the RCD trip current is the maximum allowable for it to meet its standards.

Did'nt read the Eaton article but fully I doubt this statement is entirely true. There has to be a minimum as well so you have a defined amount of allowed leakage current. Otherwise it wouldn't make sense to sell unsensitive (300mA) and super sensitive (5mA) GFIs / RCDs

If you had bothered to read the article, you would have found out that the regulatory requirement is that the device should operate at between 50% and 100% of the rated trip current, and that typical trip values for a 30mA RCD are 18-23mA, with a 2-3mA variance in repeatability for good quality devices.

Now we're rockin',
 well said mate   

Seriously folks, what part of trusting fool zone is not clear, when prodding OUCH!/HOSPITAL/BBQ/MORGUE voltages

and trusting an RCD or GFCI, you struggled to release from a blister pack   with bolt cutters and oxy cutting torch

with entitlement to a refund, exchange, or gift voucher if faulty 

This comment is mainly aimed at newbies and overconfident amateurs, and many of us have been there at one time guilty as charged

Apparently pros never get zapped terminally by RCD GFCI fails,
and many that did past and present have never returned to tell us whether it was the current, voltage,
or pacemaker failure that did them in 

[Zero999]

I notice the original poster has deleted the first post. It does annoy me when that happens. There's no point in doing this. It just implies he's gone off in a strop.

To answer the question: yes, I have one on my bench in the lab at work. Not only does it provide shock protection, as the circuit has no RCD, but it occasionally comes in handy for probing mains circuits with an oscilloscope and it reduces the leakage on switched mode power supplies. It's a useful piece of kit. Obviously I'm fully aware of the dangers and don't rely on it to provide complete protection against shock. I know full well, when the 'scope is connected, the circuit becomes connected to earth, although I often use a battery powered Owon 'scope, to prevent that.

[nightfire]

On my bench at home I have also in my apartment no RCD installed for the wall outlet- cabling is older than standards dictate mandatory usage of RCD for every layman-operable circuit.
I got my hands on ebay on a new 19" power strip from Rittal, andd mounted a PRCD plug on it, so this power strip is protected by a 30mA RCD.
As an additional benefit the build quality of that strip is solid as a tank, and together it cost me less than 50 €.

[timeandfrequency]

I notice the original poster has deleted the first post. It does annoy me when that happens. There's no point in doing this. It just implies he's gone off in a strop.

I agree. Maybe he prefers being isolated from our answers.

[MrMobodies]

Let’s put it this way: if you don’t thoroughly understand why and when you’d want an isolation transformer, and what it does and doesn’t protect you from, then you shouldn’t work on mains-powered stuff yet, specifically, things with a live chassis.

If you get one, make sure you don’t let it lull you into a sense of false security, such that you actually let your guard down around mains voltages.

I am not an electrician but it reminds me of this video:
youtube.com/watch?v=FBeSKL9zVro
The most deadly project on the Internet (Wood fracking)

10:30 with a galvanically separated
transformer all it sees is the
current flowing in the primary so if
you're in the secondary which is
reference to earth and the current is
zapping through your body to ground and
finding its way back
that's a closed loop in there it is not
seeing it in that side it thinks it's a
normal load and the circuit protection
will not trip

[Nominal Animal]

As I play with microcontrollers and very low DC voltages only, I don't have nor need an isolation transformer, but I usually connect the projects to my computer via USB while developing and testing.  Me being the butterfinger I am, I have learned to use a cheap USB isolator (ADuM3160 clones off eBay, they're direct implementations of the datasheet/appnote, with the only difference being the isolated DC-DC converter used – which I recommend checking before relying on > 100mA of current being available) between the project and the computer, just in case.  My gadgets all tend to have native USB support.

I can't really tell if I've actually saved any hardware doing this, but it calms my nerves and reduces stress levels when poking at the project while it is running and powered.  It makes development more relaxed and fun.

(The only downside is that ADuM3160 is limited to full speed, 12 Mbit/s, but faster but roughly equally simple isolators like ADuM4165, ISOUSB211, etc., are still rare enough – chipageddon – to keep high-speed 480 Mbit/s isolator prices relatively high.  My Teensies have native high-speed USB, which is nice.  I guess I'll have to build my own damn isolators?)

Anyway, I wonder how many others use such equipment to limit damage to their tools because of their own butterfingery, and peace of mind, rather than as a necessary precaution for safety?

[tggzzz]

I notice the original poster has deleted the first post. It does annoy me when that happens. There's no point in doing this. It just implies he's gone off in a strop.

I agree. Maybe he prefers being isolated from our answers.

When I spot (and remember) someone has done that in the past, any reply of mine will "quote" their message so they can't pull that trick again.

[Gyro]

Ah yes, bigfoot22, a repeat offender. I't looks as if he went round and deleted the first post on all of his threads on the 11th.  [Edit: and all of his posts]

[Zero999]

Ah yes, bigfoot22, a repeat offender. I't looks as if he went round and deleted the first post on all of his threads on the 11th.  [Edit: and all of his posts]

He's deleted all of his posts.

Here's a link to a quote of one of his now deleted posts.
https://www.eevblog.com/forum/chat/your-pet-peeve-technical-or-otherwise/msg4691378/#msg4691378

It appears he's thrown his toys out of the pram and left. Did I miss the fireworks?

[Nominal Animal]

The sad thing is, when he calms down and realizes the effects of it, and how it looks, he'll want to undo it, but will not be able to. 

[tooki]

The sad thing is, when he calms down and realizes the effects of it, and how it looks, he'll want to undo it, but will not be able to. 

I somehow doubt that reflection is one of his strengths…

[iMo]

I made myself an isolation transformer mainly for measurements with my oscope. I did it simple way - with two back to back ~200W transformers (230/34V) off my junkbox, I added a fuse, sockets and a switch. It works, what I see as a minor issue is its weight and the power consumption of the combo without a load is around 30W

[Zero999]

I made myself an isolation transformer mainly for measurements with my oscope. I did it simple way - with two back to back ~200W transformers (230/34V) off my junkbox, I added a fuse, sockets and a switch. It works, what I see as a minor issue is its weight and the power consumption of the combo without a load is around 30W

How about rewinding one of them for 230V out?

I've done that before. At first I did a few too many turns and it gave 280V out unloaded, so I removed some until I got just under 250V out, with 230V in, unloaded and close to 230V at full load.

[ebastler]

Ah yes, bigfoot22, a repeat offender. I't looks as if he went round and deleted the first post on all of his threads on the 11th.  [Edit: and all of his posts]

He's deleted all of his posts. [...]
It appears he's thrown his toys out of the pram and left. Did I miss the fireworks?

Not sure what drove his decision, but he had certainly disclosed a lot of detail about his challenging personal situation in his posts. In my opinion it was a wise decision to remove them and let that published persona disappear.

I wish bigfoot the best for his future; hopefully he gets the right support and can turn things around for himself.