Warning Mains Voltage Inside

Michael 2727

Senior Member
To Technical and others,
Is there a place or can there be a place on this forum for intelligent and productive
discussion on the topic of MAINS VOLTAGE and related subjects.

There comes a time in any good experimenter, inventor, hobbyist or DIYist's life
where something they are working on requires Mains Power or interfacing with
something that may be Mains controlled or Mains operated.

Any regular members / visitors will know the mere mention of 115V or 240V in here
will get you 101 responses of Dire Warnings of DEATH Destruction and Lawsuits.

In many cases a quick glean of the Thread / Posting will give you an idea of
the intelegence, lack of or experience of the person asking the question or proposal.


Some people do have a healthy respect for Mains Voltage and take adequate
precautions to avoid Injury, Death or Property Damage.

There are thousands of Kits, DIY Projects and Project articles written that have
in some way something that is Mains powered or interfaced to the mains supply.

The same goes for just about every Electronics Magazine who publish Projects
to Build, e.g. Silicon Chip, Elektor and Nuts and Volts to name a few.

Then there are dozens of Electronics Retailers, Altronics, Jaycar, Oatley Electronics,
Dick Smith and Radio Parts, (although the last two are mostly out of that line now I think) to name afew also, who sell patrs, kits and DIY projects that may be Mains Powered or interfaced somehow.
This is just in Australia, you know your own favourites in the UK, USA etc.

It would be a pity to see everybody put their head in the sand and say that
Mains Voltage is too Scarey, too Dangerous or too Litageous a subject to approach.

All of the companies in the above paragraphs seem to be able to cope with Mains
related Publications, Articles, Kits, DIY and projects.

So I'm asking Technical or whoever it may concern,
Could they have a word to REV-ED and their Llegal Dep to see if there is a place
on this forum where constructive dialogue on Mains issues can take place.

A few lines of HTML on a web page may be all it takes to indemnify
yourself against litigious pursuits.

For the record I am not an Electrician, I have done my "S" Licence
(disconnect reconnect) though I think it's called something different now.
And have been building stuff, some Mains, most not since I was 14 years old.
My first Mains project was the original ETI Musicolour, I still have it somewhere.

Anyway I think it would be good to have a place "somewhere" on the Picaxe Forum
where constructive information and ideas can be swapped without all of the usual
argy-bargy which detracts from the original topic in question.

WARNINGS INCLUDED somewhere above or below each thread.

Rather sticking our heads in the sand saying it's all too hard, too dangerous, too scarey.



Senior Member
I do like the idea ....But i can see a road of concern from others here as you have tried to point out yourself.

It all comes down to who is posting the information and how sound the design is.

As a Administrator of a forum (which i am not here) you have a moral duty to regulate a site with a safety prospective and also non offensive material.

It really is a can of worms, and for one would like to see the mains power section, but for the simple fact of covering one's ass i think it will never happen.

If we got rid of the lawyers and went back to everyone being responsible for their own actions then these things would be possible.


One one hand we don't want to promote or support dangerous projects.
Active dissuasion is the safest option.

On the other hand this limits mature discussion between experienced people.
Many magazines tend to put in a disclaimer or warning and just get on with it - and any 10 year old could buy a mag can't they?

Morally, I see your point, but as to the GENUINE legal situation of obligation, liability and responsibility on a Forum I really don't know.
Mmm... jury's out so far :)
Some people have said things some ley-legal things on here but I'm afraid I have a massive pinch of salt ready.
I'm no specialist lawyer and neither is anyone here as far as I know.

BUT, at the end of the day, this Forum is Rev-Ed's baby.
So whatever policy they choose will be the one that needs to be followed.

Do we include caveats (like a magazine) or do we design the Forum content around the lowest common denominator?
Certainly this will attract quite a few paragragphs...

PERHAPS you could have an 'Adult' thread on those 'alternative' PICAXE Forums that were mentioned a while ago but seem to have been forgotten...
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There are several concerns that I can see.
Firstly, this forum covers many nations all of which have different regulations and legal advice for one might be illegal in another. This is certainly already an issue even for the 'big boys' who have to maintain products which comply in all destination countries.

Secondly, who will provide the 'official' legal solution to a particular issue and how will you know that the advice given is accurate?

My personal opinion is that the need to ask is a very strong indicator that you probably shouldn't be doing it. Whilst that might sound a bit "Nanny", a full understanding of the local regulations and a sound electrical/electronic background will more often than not answer the question. Over and above that, you would be taking the word of a total stranger whos qualifications are unknown and putting your life (and that of your lawyer) in their hands.

If we had a few commercial members from 'you know where' on here so that we could educate them that simply putting on a compliance sticker does NOT make it compliant, great. However, as soon as it's realised that being compliant would increase the product cost by 10p, then they'd ignore the advice anyway.

For Rev-Ed to police such advice would require their own legal team of experts not allowing viewing of posts until sanitised. That would simply cost a fortune. Many companies avoid the problem by simply avoiding the problem and leaving to others. That is why many consumer units no longer have mains internally and rely on the use of wall-warts. The wall-wart is certified and bought in. The product consequently does not require certification except for EMC regulations, fire hazards and toxic substance compliance; all of which depend on the locality.


Technical Support
Staff member
As noted it's a complex area but does ultimately come down to duty of care, taking responsibility for consequences plus covering backsides when things go wrong and blame starts getting apportioned, fairly or otherwise.

No legal disclaimer, no lawyers' advice, will prevent someone suing someone else if they decide to and no one can guarantee what the outcome of such a claim will be. It's within that framework magazines, publishers, forum providers and even contributors ( in fact, everyone ) have to work. The only likely certainty, should anyone sue, is that everyone will say it's someone else's fault and the finger shouldn't be pointed at them.

Some magazines and forums may take a more lenient stance on some subjects, others may simply bar them outright. It all depends on what they are prepared to risk and also on what their audience is; how likely they are to understand the warnings, how likely it is that they would understand the importance of warnings, how fully they can be expected to understand the meaning and risk of any danger raised.

Few would have any issue with professional explosives experts discussing amongst themselves the most impressive way to make things 'go bang', but there would obviously be concern if all-comers were invited to such discussion knowing there will be people who will just go 'wow, sounds good" and head off to try it.

If there were a forum for mains power ( or any potentially dangerous subject ) it might be necessary or best to restrict membership to those who can demonstrate and prove competence, qualifications and authority to speak on such matters, those who can prove they understand the risks and dangers, with moderation by the same. That's perhaps something best suited to a specific forum in its own right rather than part of a general, open to anyone, set of forums.


Senior Member

As an Electrician I have mixed feeling of giving or taking advice over the interweb.....
As one of my instructors once said, you have to live with yourself and your little voices. How would you feel if someone got injuired or killed from your advice. It can happen easily enough.

I have seen the dangers and the results. Stuff which people, not in the trade, DON'T see.
Sure 99 time out of 100 things will be ok, but can you live with that 1%. I know I can't

My 2 cents worth.
Your mileage may vary.....
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Senior Member
All my initial electronics work used pre semiconductor mains powered valve/tube circuitry, & working with several hundred Volts HT (High Tension) DC was the norm. This shock hazard naturally meant a culture of VERY healthy respect & care developed. All manner of circuit devices could spoil your day, & even with the mains disconnected capacitors & suspect bleeders had to be considered. It was somewhat akin to using a powerful circular saw...

Low voltages today mean few have experienced the odd tingle associated with that era, & hence many newbies indeed may have no "feeling" for the mains. For that matter few youngsters have experienced the corporal punishment,steam scalds or hand cranking an engine.

Although mains devices are now much safer (thanks to RCDs & superior insulation etc),global variations & legal issues certainly are a modern factor. NZ & Australia have similar wiring standards (230V 50Hz) & hardware, but several Australian states have strict limitations about just what can be done by the non certified. I recall Queensland is especially strict, leading to faulty appliances being thrown out because owners are prohibited from fixing them. This tragically may mean such rescued gear could cause injury to some later tinkerer... We're relatively liberal in NZ, yet electrocutions here are rare. There are more deaths & injuries caused by ladder falls - or probably TransTasman sports matches !

A useful modern approach to the issue (& one I always use with directly mains powered student projects) is to insist on RCD (Residual Current Device) usage. These cover your liability & are cheap enough (~US$20). Furthermore they may alert to mains wiring blunders. Alternatively specify that mains circuitry must be energised by mains plug pack/wall wart,or perhaps an ex PC power supply. Stan.


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New Member
What sort of things do you want to discuss?

I try to avoid mains as much as possible, but that said, I have quite a few projects around the place that are working fine.

Ever since I found my flouro lights glowing despite the solid state relay being 'off', I have decided only to interface with mains using a good old fashioned relay. I like the ones that have wide lugs and which fit into a relay socket, as the socket then very much keeps the mains and low voltage wiring away from each other.

What I would like to see is a generic 'mains interface' box. A mains plug on one side, on a cable. A mains socket on the other side, either on a cable or on the side of the box. A relay on the inside with a 5 V coil, and some sort of standard low voltage two pin plug to power that relay.

Never open the box, it is nice and safe, and easily interfaced to a picaxe chip.

I've built such boxes myself, but I wonder if such a thing is available commercially?

Michael 2727

Senior Member
Dr Ac your Flouro was probably running off capacitor leakage through the snubber circuit.
Get a data sheet on one of the many Fairchild Optoisolators e.g. MOC3XXX series they
usually include a full SSR application circuit. Other Mfgrs may have similar data sheets.

(L) ----[/\/\/\/\]-------||------- (N)
39R 0.01uF


I'm pleased you have discovered that semi switches leak , DrAc :)
Most novices think that triacs (and similar) are perfect on-offs.

What is the purpose of the relay in your box?

Is there nothing similar on the Market? You Aussies are nearer to Cheapsville. Surely there's some dreaded box bursting from a sweat shop somewhere over there?

I'd like to see something smarter for a few extra pennies.
A simple op-amp circuit (or PICAXE) could allow an adjustable trip.

People shouldn't kid themselves they can do it commercially as they couldn't afford the testing/Approvals/maufacture required.

I'd better stop there. Apparently I shouldn't be discussing such things here as it might encourage novices to try it.
I'll have to discuss it on a 'Grown Up' Forum (which I can delude myself that youngsters don't read). ;)


New Member
Thanks michael2727 - that probably was the problem. I've gone for relays ever since.

Re Dippy - the purpose would be to be able to control mains voltages without having to worry about ever touching mains wires.

Re Is there nothing similar on the Market? You Aussies are nearer to Cheapsville.

Tehe, we are nearer than you think. In fact, we just dug up all of Australia and sold it. We are heading north in a big boat as we speak. Possibly explains bizarre things like the global financial crisis not affecting Australia, and our currency being worth 0.99624 US dollars. It was 0.47 when I was a kid. I can see, to quote Monty Python, that my sunburnt spendorous Aussie dollar will also buy 62 pence, and that was 33 pence when I was in short pants.

I thought of another solution. It involves going to a website starting with e, (hope that is ok), but for $18 and if you live in the USA, you can buy a wireless remote mains controller. http://shop.ebay.com/?_from=R40&_trksid=p3907.m570.l1313&_nkw=wireless+mains+switch&_sacat=See-All-Categories

That would be 110 volts, so you would need a local version, but what you could do is hack the wireless remote to talk to a picaxe as that would all be low voltage. The mains part stays sealed up in its box, which is exactly what we want for a safe mains controller.

So the next question - apart from turning mains things on and off, what other mains things might one want to do? I guess there is variable speed control and variable frequency AC but I suspect the vast majority of control would be On/Off.
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Senior Member
Yesterday (or was it the day before) the A$ got over US100 cents for the first time since the 80s I think.

It stayed above parity for 7 seconds then dipped back into the 99s.

But they reckon it will get to 1.10 or higher. Looks like a trip to the US is on the cards :)
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Me: "What is the purpose of the relay in your box?"

DrAc: "the purpose would be to be able to control mains voltages without having to worry about ever touching mains wires"
Do you mean adjust the mains voltage or connect/disconnect the mains?
What's wrong with a switch?

Anyway, doesn't matter.
Bench power supplies of various qualitites and prices are available.
I'll stick to Big Boy brands.

Back to the plot.
Yes, I'd like to be able to discuss mains and car projects here.
But if the Forum owners have a set of rules then that's what should be followed.
This subject has cropped up many times.
A directive from Rev-Ed would be nice to settle it once and for all.
After all, no-one else has the 'power'.

Michael 2727

Senior Member
One word, Automation.

Sometimes you need Silent Switching, imagine an Intensive Care Ward (ICU) or (CCU)
with 10 patients and each having a dozen Relays to control various devices.
The place would sound like the old style Telephone Exchanges, you needed ear
plugs in them.
Theatre lighting, Shhhhhh !

Dr Ac, Triacs leak a tiny amnout also as Dippy pointed out.
It doesnt lake a lot to make a Fluoro glow in some cases.

Dippy you had better watch it, the Nannies with Black Puddings will
have you on the Ecky Thumpin List. I'm prolly a marked man by now.


Well, doesn't that relate to the El Cheapo mains switch thread?
Just override the remote control end buttons or hack and bingo.. you have a wonderfully safe, fully tested and approved Chinese made Mains Switch.
What could be better? If you want cheapo that's what you'll get.

Quality costs extra - but people don't care about quality of their wallet is at risk.

But mains work is like coitus; it's easy if you know how, but sometimes you may need to take precautions and it can lead to injury.


New Member
I like the idea, and I do have the licences, but remember that the Picaxe is designed for teaching purposes which would tend to preclude anything to do with mains, I get very worried when somebody is discussing mains voltages and it is very apparant that the person is not competant with mains.

I know most here in this thread would be ok with mains (I'm a long time lurker...) and we could discuss it with no dramas, I think that for safetys sake, it best be kept out.

Oh, and Manuka, I love your "Trans Tasman sports matches" The Bledisloe Cup is THE hardest Rugby anywhere, you're also correct about Queensland, very strict.


Big problem innit. We need guidance from Rev-Ed.

We need to know the definition of dangerous and who will be referee.
Some people panic over trivial things and some take a very sensible real-world attitude towards the definition.

Everyone tut-tuts when Cars and Mains is mentioned.
That's entirely understandable as both are potentially fatal , but equally, both are fine in the hands of trained/experienced people.
But we don't bat an eyelid when Dustbin sized Mega-Farad capacitors get airtime. Connect a few of those together , charge them and shove them where the sun don't shine and it could be Goodnight Vienna.

Maybe regular users shouldn't START threads with a certain range of subjects, BUT should be allowed to respond to novice questions?
Surely sensible instruction is part of being responsible?

Maybe erring on the side of caution is best? Afrter all, when Bloggs posts a thread we don't know whether he/she is a fully qualified genius or that spotty schoolboy who think he knows everything.

Ah well, this is all going round in circles now and getting nowhere quickly.
No doubt it will get another airing in a few months so I'll get back in my coffin.:p