How do I wire this?

[Karel Bata]

Hi,

I've got an old mirrorball here that needs a little repair. The motor has four wires - red, yellow, and two black - that run to two orange rectangular things that could be diodes (?). I'm clearly no expert. From these emerge a blue and white wire which have bare ends. I know these go straight into 240V or 110V (it says so on the motor!) but...

Blue and white - which is live and which is neutral? http://www.blue-room.org.uk/public/style_emoticons/default/unsure.gif

Thanks! http://www.blue-room.org.uk/public/style_emoticons/default/biggrin.gif

[nuttytechy]

Those orange things are not diodes. They will be capacitors.

 

As this is made by the Chinese then good luck. It won't matter what polarity it will be as both wires will go to the contacts for the motor.

 

I very much doubt there will be an earth and if it is a metal housing with no earth then it will fail a PAT test so won't be allowed to be used in the field.

[Karel Bata]

Thanks. It has got a decent earth connection, just not running to the motor.

 

[Ynot]

....if it is a metal housing with no earth then it will fail a PAT test so won't be allowed to be used in the field.

Unless I'm mistaken (I'm NOT a PAT tester but know the basics) that's not quite true.

 

The PAT is NOT a legal requirement for equipment to be usable - though it's often touted as such by less aware (or unscrupulous individuals/companies/venues) but it is pretty much like an MOT on your car. There is NO law that says your electrical kit MUST have a PAT certificate, although common sense would suggest that it's a good start.

 

However, as a Chinese import, there ARE laws that stipulate that items must have a valid CE marking/registration before they can be legally sold in the UK, but that is completely different from PAT.

 

I'm sure others will be along soon to confirm or refute my ten pen'orth... :)

 

 

 

[Karel Bata]

This is rather like EU regulations that plumbers throw at you. Much is hearsay. Look them up and they're not what the urban myth would have you believe.

 

Venues (and various jobsworths I could name) can insist on seeing a PAT test sticker. But that's all it is - a sticker. You can buy thyem eBay. A few years since I Ilooked this up, but the law says that equipment needs to be checked regularly and by a comptenet person. As vague as that. I can PAT test it myself, as can anyone else that is competent.

 

Exceptions, and there are many, will be big companies (that are often litigation wary) and will often decide on a strict interpretation and impose a schedule and who this ceompetent person may be.

 

I inspect my own gear, put my own PAT stickers on and everyone's happy. The jobsworths just need to see a sticker.

 

Certainly there's a lot of rubbish you can get from China, but they've come a long way of late and also make a lot of quality gear. Look at the back of your iPhone: "Designed by Apple in California. Assembled in China." http://www.blue-room.org.uk/public/style_emoticons/default/wink.gif

 

 

Blue and white? http://www.blue-room.org.uk/public/style_emoticons/default/blink.gif

 

[Jivemaster]

As it becomes a two wire motor after the capacitors are fitted, it doesn't matter which way round it's connected! The capacitors should give start and maybe direction to the motor whichever way it's wired. It will be just as CE (China Export) compliant whichever way you wire it. Yes an earth would be an improvement.

[ImagineerTom]

Yeah erm.... you say you’re a competent person who’s suitable for inspecting / pat testing but you can’t tell the difference between a diode and a capacitor and you’re having to ask strangers on the internet how to wire up a 2 wire AC device. If any of your equipment is involved in a claim they’re going to dig up this post as proof you’re not competent and very quickly your insurance and indemnity will disappear.

 

If you take nothing else from this conversation it should be that you need to get someone else with a higher skill set than you to test/inspect your kit.

[Karel Bata]

Good grief Tom. So no one here should ever ask technical questions because they're 'strangers on the internet'?

 

The very fact that I'm asking shows that I'm aware of the holes in my knowledge. It's being aware of your own limitations, rather than just crossing your fingers, that is a mark of a competent person. I asked here (and copy and pasted to a few other places) because I assumed there would be a few knowledgable people here. I also wouldn't act on simple advice like 'blue is always neutral' as I want to hear some reationale behind that, and would want to hear the same advice from several people being continuing. I regard that as part of competent practice.

 

If an astronaut looks at some wiring and thinks "What does this connection do? I'd better ask." does that make him/her incompetent? (Only if it's Sandra Bullock). The fact that the advice I've recieved has been argued from a logical permise rather than any wiring regulation shows that no one here recognises this as any form of standard, so no high level of familiarity with wiring standards (nor knowing capacitors from diodes) would have answered this question.

 

As it happens I have been to court arguing that someone else's wiring was incompertent (on a boat). Evidence gleaned from the internet and stuff pulled from boating forums was seen as totally acceptable. The judge didn't dismiss it as advice from 'strangers on the internet'. The plaintiff had the opportunity to prove the evidence wrong, but couldn't. I've done many elactrical repairs on the boat - I knew nothing about echo sounders or making fibreglass when I started, but I do now from asking on boating forums. They are very helpful. More skilled repairs I leave to experts. A perfectly reasonable approach.

 

In this case I had a feeling it didn't matter, and logic told me so, but I couldn't be certain what was inside the motor/gearing, so rather than take that apart asking on forums which of these wires is live or neutral is a sensible, and competent, thing to do.

[Shez]

if it is a metal housing with no earth then it will fail a PAT test so won't be allowed to be used in the field.

The DVD player sat under your TV has a metal housing but no earth - should that fail too?

If it's designed properly as a class II appliance, no earth connection is necessary, even if the case is metal.

 

(Caution is of course prudent with some of these cheaper Chinese items - as some of Big Clive's videos demonstrate, their earthing practices aren't always quite up to the standards one would hope for!)

[Karel Bata]

But it is earthed. Never said it wasn't...

[timsabre]

Good grief Tom. So no one here should ever ask technical questions because they're 'strangers on the internet'?

The trouble with this forum is that it's hard to tell the difference between someone competent who just needs a bit of help with something they haven't seen before, and someone like Davie Dimmers who will go off and hot wire their bedroom to the national grid. As we don't want to anyone to electrocute themselves or others, advice is sometimes over-cautious.

 

[Karel Bata]

Totally. http://www.blue-room.org.uk/public/style_emoticons/default/dry.gif Which is why I wanted to hear the logic behind the advice, and from more than one person. I assume there's more comptence here though than I would find at the X-Box forum... http://www.blue-room.org.uk/public/style_emoticons/default/huh.gif

[paulears]

I'm clearly no expert

 

Seems fine with me. It does indeed look a bit weird to somebody expecting two wires to run straight to the motor, so I think it's a fair question.

 

Actually - Big Clive's channel is an excellent way to understand how some of the Chinese designs actually do pretty clever things a bit craftily. Especially the ones where he pulls something apart and then details how the circuit works. He gets surprised too on many occasions by the innovative ways they do things - I watched a great one on a faulty led string light - where all the individual filaments inside the glass appeared to be in series - and he worked out that this meant it would need over 600V to light them up - and that's exactly what the circuit inside did!

 

My experience with Chinese things is that they don't pay much attention to earthing at all. Metal cases could easily be grounded, but never assume they actually are. Sometimes inside there's even a ground connection - but the box isn't drilled to bolt the tag to.

 

We diverted into PAT - which is always a bad move as it produces so many arguments, we also crept into CE=China Export, which is a European explanation of something that doesn't exist. Tiny changes in font, and we're convinced CE is not the standards mark and is some kind of Chinese export marking. One of my Chinese sources laughed when I asked a question on it. The CE marking on most cheaper, short run products is simply stamped on, and any paperwork simply printed off with old product text deleted and new one stuck on - just the same as happened years ago with BS Kitemarks. We shouldn't get uptight about this. I PAT new stuff, and occasionally one fails - usually because the chassis is missing the earth. Fixing it generates a PAT pass. Do we need to go further? We're quite happy building our own bits and pieces at whatever technical level we are competent at individually. I can't see much difference with Chinese kit - once you take sensible precautions, and don't see the CE mark as a PAT pass.

[timsabre]

Look up "AC synchronous motor" and all will be explained. But basically it does not matter which way round you connect the blue and white wires, when you energise it from stationary it will rotate in a random direction.

If you are old enough to remember Optikinetics sound animated projectors, they used this principle to make a rotating projection mask dance backwards and forwards in time with the music.

(PS as you say I believe the "China Export" thing is a myth. They are just slapping on an inaccurately printed CE mark.)

 

[Karel Bata]

I think the extra capacitors and wiring are to do with handling both 110 and 240 AC without needing an in-between stage. Not my area though.