Arduino Relay Board

===============

** Very naive idea. ** You don't know that.

** Think you know SFA - pal.

Relay contacts for 250VAC open about 1mm in practice. The DC rating is only 24V for the same relay at similar current - cos DC acrs do not self extinguish.

User safety is a separate matter and has got nothing to do with a device simply working. The issue then is whether a dangerous voltage from the MAINS SUPPLY can get across the gap from contacts to the coil. For this, there are two questions:

Is the coil side wiring supply earthed ? Can a user be in contact with the coil circuitry with no safely earth ?

If no earth, clearance and creepage apply - distances an acr or "tracking" could breach some day allowing for some contamination of the PCB or relay itself. This link from Sylvia showed a relay that would likely meet the second condition:

Just looking at logos on a relay tell you nothing. User safety is way more involved.

The relay Sylvia "sacrifised" looks a safety nightmare .

...... Phil

Yeah, sure. Don't worry about those relay boards they're completely safe and meet all safety specs. The law says so, therefor they do.

Not sure what you intend by that. Laws are human creations, and can be breached. People who breach laws can be punished. It is not a defence to say that the product was cheap.

Sylvia.

I agree, this is misrepresented saying it can control 220VAC loads. The RELAY is indeed safety rated at 10A @ 250VAC, but the board layout has no approval rating, so must be operated under 30VAC.

I submitted an 'incorrect product information' report on this item.

Usual problem with eBay and Amazon products, no accountability.

John :-#(#

John Robertson wrote: ===================

** Means only that it can switch that voltage at that current. Takes no account of many thousand volt spikes that can occur on the MAINS supply for a variety of reasons. Such spikes will possibly bridge the contacts and or the gap between them and the coil terminations on the bad relay that Sylvia bought. Once the gap is bridged a vert large current can then flow.

It also takes no account that the coil side may be in direct contact with a user. Safety involves the WHOLE set up.

...... Phil

Even if the coil side power supply is earthed, it still might not be compliant with safety standards. If one end of the coil is earthed, it has to be a protective earth, not just any weedy earth wire, the test for this depends on the standard for the end product but is often something like passing 15A or 25A for a minute. (I'd suggest something like 400A for 5ms might also be a relevant test but the standards don't require it.)

Even if one terminal of the coil is protectively earthed, if the other end of the coil goes to the arduino etc. then it is still not compliant. Both ends of the coil can't be protectively earthed if you can turn on the coil, so at least one end needs to have some mains-rated insulation from the user in order to be compliant. If the arduino is accessible to touch then this is no good.

The only way that I can see this relay board could be used in a compliant product is if the whole arduino and everything connected to it is classed as mains circuitry and separated from the user by reinforced ("double") insulation (~5mm creepage, depends on which standard) or basic insulation (~2.5mm creepage) to a protectively earthed enclosure. Of course then you can't plug in a laptop or anything else to the Arduino for programming it whilst being compliant.

Given that the typical Arduino user won't know anything about this, it is irresponsible to be selling this thing, particularly as it could have been made safely for about the same cost.

Phil Allison snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:

1000 volt spikes on your power line? I have serious doubts about that claim. Maybe back in the sixties when you thought you knew electronics or power back then. I'd bet that was how long ago you looked and drew that lame conclusion. Nowadays... I seriously doubt it, and I seriously doubt you have looked at how clean an AC line is in decades.

A city boy aren't you?

Ever heard of rural power, you know where power wires extend for kilometers between customers? Small towns in the middle of nowhere that are fed by HV transmission lines?

I regularly repair equipment that has had surges, mostly from the interior of BC or Alberta (Canada) where spikes are not uncommon and most folks, if they want to preserve their equipment, use power bars with MOV surge arresters installed. And these MOVs blow up from time to time.

As Phil says, the system must be rated by a proper standards association to be safe to use at the rated voltage. And as I said, as it is unrated, therefore it is only safe for 30VAC or less.

For 120VAC the Hi-Pot test is usually be conducted at 1240VAC, for 220 it would need to not arc over around 1440VAC - "As per IEC 60950 the basic voltage for Hipot test is 2X (Operating voltage) + 1000V."

I seriously doubt this PCB will pass that insulation breakdown test.

John :-#(#

Chris Jones wrote: ================

** Bullshit.

** FYI smartarse:

"safety earth = "protective earth" !!!

** More bullshit - try reading what I ACTUALLY wrote !! " Is the coil side wiring supply earthed ? Can a user be in contact with the coil circuitry with no safely earth ? " ** Childish drivel.

( snip pile of absurd crap )

This bloody IDIOT does not know how earthing an appliance works.

..... Phil

Phil Allison snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:

Perhaps, but not thousand volt levels short of a lightning strike on a line.

Yes, we have surges. Here is the US data, republished by the US Govt:

.

"A Guideline on Surge Voltages in AC Power Circuits Rated up to 600 V", François Martzloff, General Electric Company, Schenectady NY, Reprinted, with permission, from Proceedings, 3rd International Symposium on Electromagnetic Compatibility, Rotterdam, 1979.

Joe Gwinn

If you meant "protective earth" when you said:

then you should have said protective earth. People earth things for all sorts of reasons. Some people reading your post would not know the difference.

The circuitry might have a protective earth connected to its 0V rail, maybe you would then say the circitry has a protective earth, but that is not good enough if parts of the circuitry other than the 0V rail can become live, which you know of course, but didn't say.

** WRONG !!!.

Safety earth is as * clear a term * as can be.

** Go f*ck yourself - you assinine PITA PEDANT.

.... love, Phil

Except the third bullet selling points says specifically "Control DC or AC signals can control the 220V AC Load " Irregardless of what is mentioned in the comments or questions, the company/individual selling this is misrepresenting what it is capable of. That is illegal and the add should be pulled - but this is Amazon and even if the item is not available for sale right now they won't turn the add off as a dangerous product as they won't have a chance of making money otherwise. Amazon doesn't give a rat's ass about culpability - they are not accepting responsibility for the products sold on their venue. Until that happens this sort of misrepresented item will continue to be available and I am pretty sure people will die or their homes destroyed due to dangerous products.

John :-#(#

You're confusing defense with common sense.

cheap trash is cheap trash. It will not be made well or correctly.

An Arduino is a test-bench bare board, not a consumer product. The sale of a 'thing' which is a disembodied component is not at all consistent with consumer product marketing, in terms of any safety considerations. Every bit of wire is 'not safe' in some sense, and a wire affixed to an AC cord is therefore... not a consumer product. I've got a bushel of such wires next to the test bench...

whitless IDIOT bullshitted again : ======================

** 100% IRRELEVANT !!! ** ABSURD CRAP !!!

The relay board is being sold as a safety related device ! To SAFELY switch the AC supply ( on / off) from a popular hobby PCB controller.

Every AC rated relay I have ever bought and used could do that job well - isolation from coil pins to the AC carrying conductors is huge. The one Sylvia "sacrificed" is not safe for that job.

...... Phil

[The issue then is whether a dangerous voltage from the MAINS SUPPLY can get across the gap from contacts to the coil. ]

Imagination is required; open your mind and use some.

No, the relays don't come attached to any AC supply. That's a user decision, not part of the as-delivered item.

24VAC is common in power control systems, as are SSR devices with low DC voltages on the inputs, and the relays would safely drive those. They'd work in a car, on 12V. You can argue safety after you know the application, but not just by looking at the relay and the Arduino. For aircraft, none of the considered relays are safe at 10k feet...

whitless SICK DEMENTED IDIOT bullshitted again :

======================================

** This vile ASD f***ed pig needs shooting !

** Your total f****ng INSANITY is your ONLY point. ------------------------------------------------------------------------------ ** WOT FUCKING INSANE FUCKING CRAPOLOGY !!!!

INSANELY TOTALLY WRONG !!!!!!!!!!!!!!!!!!!!

GET cancer & die you POS f****ng asshole.

YOU are NOW MY TARGET ------------------------------------------

..... Phil