Electronics > Beginners

Floating the DUT

<< < (4/4)

tggzzz:

--- Quote from: fcb on January 28, 2020, 06:24:00 pm ---
--- Quote from: tggzzz on January 28, 2020, 05:16:21 pm ---
--- Quote from: fcb on January 28, 2020, 04:45:45 pm ---It's certainly classic to 'lift' the ground (disconnect) of a scope in the good old days. It was also frowned upon by management, but widely ignored.  When PAT testing became a thing, you would reconnect the ground, wait for the PAT test to be done and then disconnect again. Times have moved on and scopes have switching supplies in them that leak to ground so wouldn't do it; and we have diff. probes, low cost battery scopes etc.

--- End quote ---

It may be classic, but newbies should be aware of the info in https://www.eevblog.com/forum/projects/isolation-transformer-for-scope/msg2259465/#msg2259465 especially the "example fatality".

--- End quote ---
I should also have said DON'T do it. Ensure your equipment is grounded correctly - including 'scopes.

--- End quote ---

Your "don't" was implicit, but for newbies being explicit might be useful :)

ArcticPhoenix0:

--- Quote from: james_s on January 28, 2020, 04:33:27 pm ---What exactly are you trying to do?

--- End quote ---

Right now I'm trying to safely explore and learn how to use my tools and figure out what does what while staying safe. I'm naturally curious about this kinda stuff and I want to make sure I don't get myself into a situation I'm either not equipped or experienced enough to handle.

I realize that I enter an inherently dangerous situation just by removing the cover off certain items. I've been bitten by a few digital cameras so I understand that just because it's "off" doesn't mean it's not charged still.

Going back to my original post, I said that I know just enough to be dangerous. I'm intelligent enough to know that things plugged into the wall can be deadly but at the same time I know that there's a correct way to go about dealing with those things. So, in essence, I'm trying to figure that out with a minimum of collateral damage.

james_s:
I would say that you should for now avoid anything mains powered entirely if possible. Items that are powered by one of those "wall wart" or inline power adapters are ok as those are isolated and provide the device with low voltage.

Once you know your way around inside something it's generally ok to test mains powered devices as long as you stay on the secondary side of the power supply, but an important caveat here is that there are some kinds of devices that are not isolated. Because of that I consider this to be expert territory, best to just stay out of this stuff entirely, at least keep the scope out of it until you are 100% confident at determining what is safe and what isn't.

tggzzz:

--- Quote from: james_s on January 29, 2020, 01:04:36 am ---I would say that you should for now avoid anything mains powered entirely if possible. Items that are powered by one of those "wall wart" or inline power adapters are ok as those are isolated and provide the device with low voltage.

--- End quote ---

Provided you don't use one of these wall warts...

"New Which? research has uncovered dozens of dangerous USB chargers, travel adapters and power banks listed for sale on AliExpress, Amazon Marketplace, eBay and Wish that could cause fires, give electrical shocks and potentially harm or even kill consumers. In a new investigation, more than three quarters of the 35 products from ‘unknown brands’ – those our experts didn’t recognise – that we purchased from online marketplaces, failed our electrical safety tests.... Eight of eleven lookalike brands failed standard safety tests.... Seven of these products also failed to pass standard electrical strength tests. And for one unbranded charger with three USB ports bought from AliExpress, arcing could be heard – this is where electric current flows through the air.... We tested 12 USB travel adaptors by unknown brands bought from online marketplaces Eleven of the adaptors failed electrical safety tests,"

FFI see https://www.which.co.uk/news/2019/09/killer-chargers-travel-adaptors-and-power-banks-rife-on-online-marketplaces/

For most purposes where you are debugging your own designs, use a bench power supply. They are cheap nowadays, and the current limiting can be highly beneficial.

Navigation

[0] Message Index

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod