AC series-wiring special dimmer switch/remote control, but lights no longer come on

[JohnW2]

Yes. (not a very good picture) ... I don't know how it works.

Fair enough. It obviously must 'work' by virtue of capacitive coupling (presumably to earth, not neutral) from the device itself.

However, as I said, I'm rather surprised that it works - but, as I also said, given that it does work with what must be a very small capacitive coupling to earth, I would expect that, when it was being held (thereby probably substantially increasing the path to earth) it probably would indicate in response to very 'tenuous' voltages - such as those resulting from capacitive or inductive coupling between cables/conductors. As you go on to say ...

Possibly - as it is also a non-contact detector when holding the tip (or touching the other end) - but then, don't use it for anything hazardous.

If it can do non-contact detection, it must be pretty 'sensitive' (much more sensitive than a 'contact' detector needs to be) - since there is an additional impedance (capacitive reactance) between the device's tip and the voltage source. That reinforces my suspicion that, when 'held and connected', it could probably easily light up in response to 'spurious' voltages (induced or capacitively coupled).

Kind Regards, John

 

[ban-all-sheds]

I certainly have some - but I'm not a 'qualified electrician', so that doesn't really count!

Well I don't.

I'll admit to having owned them in the past, but as they were all piggin' useless as screwdrivers they got binned and not replaced.

I do have a magic wand somewhere and I did once find it genuinely useful.

 

[JohnW2]

I certainly have some - but I'm not a 'qualified electrician', so that doesn't really count!

Well I don't.

Fair enough - but you're not a 'qualified electrician', either - so, like me, you also "don't count"!

Kind Regards, John

 

[ban-all-sheds]

I've got the Domestic Installer NVQ....

 

[JohnW2]

I've got the Domestic Installer NVQ....

Good for you

Kind Regards, John

 

[ban-all-sheds]

So all I need now is early onset dementia...

 

[stillp]

I thought that was a prerequisite for DIs?

 

[333rocky333]

Fair enough. It obviously must 'work' by virtue of capacitive coupling (presumably to earth, not neutral) from the device itself.

However, as I said, I'm rather surprised that it works - but, as I also said, given that it does work with what must be a very small capacitive coupling to earth, I would expect that, when it was being held (thereby probably substantially increasing the path to earth) it probably would indicate in response to very 'tenuous' voltages - such as those resulting from capacitive or inductive coupling between cables/conductors. As you go on to say ...
If it can do non-contact detection, it must be pretty 'sensitive' (much more sensitive than a 'contact' detector needs to be) - since there is an additional impedance (capacitive reactance) between the device's tip and the voltage source. That reinforces my suspicion that, when 'held and connected', it could probably easily light up in response to 'spurious' voltages (induced or capacitively coupled).

Kind Regards, John

Ive had a few of them, I thought they just work like a normal plastic voltstick, just encased in a screwdriver body for added convenience.

I just hold mine by the glass body near an electric field and it lights up, often i hold it by the blade tip and just hover the handle end near the live source, or sometimes just lay it near a live source, theres no need to touch the blade end on the live part.

It also lights when held near the output from a 12 volt lighting transformer and often glows when near electronic items or supermarket door security scanners

Though I do recall it is brighter if you do touch the actual blade on the live, but i rarely do that..
Im also not sure that if you do touch the blade on a live source, you should also touch the other end, you dont get a shock, but the continuity function could kick in and light the neon misleadingly.

As Efli says the continuity function alone is handy and the screwdriver is quite robust too.

Its really a voltstick, continuity tester and a screwdriver in one.
I highly recomend them to both Handyman and Trade.
Like efli, i have had the "other type" come in a kit, though only used them as a driver and never found the handles comfortable usually rough

 

[JohnW2]

Ive had a few of them, I thought they just work like a normal plastic voltstick, just encased in a screwdriver body for added convenience. I just hold mine by the glass body near an electric field and it lights up, often i hold it by the blade tip and just hover the handle end near the live source, or sometimes just lay it near a live source, theres no need to touch the blade end on the live part.

Indeed - but, as I said, having a 'non-contact' capability is a likely to be a two-edged sword. Whilst it's obviously desirable when one actually wants a non-contact device, the increased sensitivity required to achieve that almost certainly means that, when one uses it in a 'contact' mode, it is going to more susceptible (than 'contact-only' devices) to lighting up as the result of spurious (induced or capacitively-coupled) voltages.

Kind Regards, John

 

[EFLImpudence]

That may be true but we're not using them for testing for dead.

They may be no more reliable for that than the neon ones but the other uses are very handy - and, as usual, you are extending the discussion to include that which is not relevant to the original point(s).

 

[JohnW2]

That may be true but we're not using them for testing for dead.

I realise that, but it would be unhelpful if, due to the increased sensitivity, such a device lit up (even with the switch 'off') on both the L and S/L conductors one was trying to distinguish between.

Personally, if I was wanting to use such a device, if I had access to conductors or terminals I would preferentially use one (i.e. neon) which did not have a non-contact capability, and would use the latter only when I needed the non-contact functionality. However, maybe that's just me.

Kind Regards, John

 

[endecotp]

It can only be capacitive coupling can't it?

In this post: //www.diynot.com/diy/threads/huge-voltage-drop-between-switch-and-fitting.454067/#post-3592283
I estimted the impedence from earth to an adjacent conductor to be of the order of 30 Mohm.

If your body had 0 impedence to earth, the current that would flow would be of the order of 300V/30000000R = 10 uA.
"The Internet" says the limit of perception is around 1 mA, i.e. 100X higher.

One possibility is that there is resistive leakage in the cable or associated gubbins, e.g. another nail or similar.

(Can someone please check my maths?)

 

[JohnW2]

In this post: //www.diynot.com/diy/threads/huge-voltage-drop-between-switch-and-fitting.454067/#post-3592283 I estimted the impedence from earth to an adjacent conductor to be of the order of 30 Mohm.

That was a (seemingly correct) calculation of the approximate impedance of the capacitance between two 2mm diameter conductors, 0.5mm apart and 2m long, so I don't know whether it is necessarily directly relevant to the present discussion.

If your body had 0 impedence to earth, the current that would flow would be of the order of 300V/30000000R = 10 uA. (Can someone please check my maths?)

Your (approximate) calculation appears to be correct.

"The Internet" says the limit of perception is around 1 mA, i.e. 100X higher.

Yes, that is the commonly quoted figure. I think some people can feel a bit less. To get 1mA from a 230V supply would obviously require a total path impedance of about 230kΩ - which if that was all capacitive reactance would equate to around 15nF (i.e. 15,000 pF or 0.015 μF) at 50Hz - an awful lot for 'stray capacitance'.

Kind Regards, John

 

[ban-all-sheds]

He's got dodgy wiring, and is more concerned with keeping his floors intact that sorting it out, and that's all there is to it.

 

[EFLImpudence]

I realise that, but it would be unhelpful if, due to the increased sensitivity, such a device lit up (even with the switch 'off') on both the L and S/L conductors one was trying to distinguish between.

They don't seem to do that.
However, as with the neons, you have to interpret the results.

Personally, if I was wanting to use such a device, if I had access to conductors or terminals I would preferentially use one (i.e. neon) which did not have a non-contact capability, and would use the latter only when I needed the non-contact functionality. However, maybe that's just me.

The non-contact method gives totally different results.
That is - holding the tip and holding the tester near a voltage, it lights but there is nothing the other way until actual contact with a live part.