Shock from Dyson handheld battery vac...

[Deuce]

So, here is one to debate.

Wifey bought one of the cordless V8 dyson vacs, on the basis that all her friends have one. It's pretty handy.

But today I discovered an unusual feature. If it detects the motor is working too hard (in this case as the filter was blocked with dust), it will switch off until you release the trigger. However... As it cuts out it sends a hefty shock back out the charging port, sufficient to transfer into the palm of the user - in this case, me! After the first and second shock, I took it over to a radiator and held the charging port next to it, sure enough each time it cut out it would arc to the radiator. Each time I released the trigger before it cut out, no arc.

So, did Dyson protect against this problem, but only if the trigger is released, not if the vac cuts itself off - basically an oversight? Or is it perhaps some cruel way of forcing the user to clean the filter?

I did google, found this and others: https://forums.whirlpool.net.au/archive/2531043

Theories? I suspect the stupidly fast (100,000+ rpm) motor builds up quite some floating voltage which might be responsible for this 'feature'.

 

[buzzlightyear]

Wifey bought one of those cordless V8 dyson vacs, on the basis that all her friends told her to get one for me . It's pretty handy. has I'm domestic slave and now chained to it

corrected that for you .

​

 

[Deuce]

corrected that for you .

​

Ah ha!!! But now it's proven to try and electrocute me, I have solid H&S grounds for not using it anymore!!

At least until she risk assesses it and provides me suitable PPE. I assume, marigold gloves

 

[buzzlightyear]

So, did Dyson protect against this problem, but only if the trigger is released, not if the vac cuts itself off - basically an oversight?

not really they want you to buy their C77p stuff. its like all DYSONS gear it ways a ton . or stops you from using it after it picks up a dust.

 

[Deuce]

not really they want you to buy their C77p stuff. its like all DYSONS gear it ways a ton . or stops you from using it after it picks up a dust.

It is, all said and done, a vacuum that switches itself off if it detects it has sucked up dust. Not exactly progress!

 

[DPG]

Back emf from the motor? I'm sure I've seen this when the plug from a mains hoover is picked up and the pins are touched immediately after switching off.

 

[PEG]

You knew where you were,with a Kirby...3 grand,half a tonne,and no need for gym membership

 

[Deuce]

Back emf from the motor? I'm sure I've seen this when the plug from a mains hoover is picked up and the pins are touched immediately after switching off.

That's my theory - and for sure, unplug a mains vac without switching it off first and you will often see a flash.

What gets me is that dyson knew this could happen and engineered against it (I'm guessing when you release the trigger, it's snubbed by a capacitor which is discharged the next time the trigger is pulled), but somehow managed to NOT incorporate that snubbing in the scenario where the vac turns itself off due to motor overload.

 

[buzzlightyear]

That's my theory - and for sure, unplug a mains vac without switching it off first and you will often see a flash.

and I'm sparked out on the floor .

 

[Strima]

Back emf from the motor? I'm sure I've seen this when the plug from a mains hoover is picked up and the pins are touched immediately after switching off.

I've had it from a bench grinder years ago, my boss was very tight and we only had one socket outlet on the bench where the grinder and buffing machines were so we always had to swap plugs over, I only covered both pins with my hand once...

 

[Deuce]

A lot of people put it down to static, which to be fair could be the case with those brushes spinning against a carpet...

But in reality, anyone that has ever seen a motor

I've had it from a bench grinder years ago, my boss was very tight and we only had one socket outlet on the bench where the grinder and buffing machines were so we always had to swap plugs over, I only covered both pins with my hand once...

The voltage in question is probably quite terrifying, the flyback can be as much as 10x the supply voltage...

Luckily it is also fleeting, and at the same time it flashes to your hand, it's also inevitably flashing to the earthed pin which is still connected to the socket in that instant.

My first experience of this was actually lifting a running train off an old AC model railway kit my Grandad gave me. Christ knows what voltage AC it ran on, back when he bought it I know some sets were at least 30v.

 

[static zap]

I know all that air flow + plastic loves making static ...
a) How long is spark ?
6mm 1/4 Inch -approx. 10kV in air
.from sharpish edges.
b) Does it stop sucking very suddenly
/or diminish slowly ?
( Early Dysons were also renowned for it in dry houses with the heating up high )
.. may be a winter dry thing ..

 

[Deuce]

I know all that air flow + plastic loves making static ...
a) How long is spark ?
6mm 1/4 Inch -approx. 10kV in air
.from sharpish edges.
b) Does it stop sucking very suddenly
/or diminish slowly ?
( Early Dysons were also renowned for it in dry houses with the heating up high )
.. may be a winter dry thing ..

Static from vacs imo is unpleasant, but fleeting. This left a bit of an ache... I'm pretty certain it was flyback from the motor.

It stops instantly the moment it detects too much resistance. As the motor is digital, this is very easy to detect electronically.

The charge socket sits slightly below flush of the casing that I had pinned to the radiator, I would say 1-2mm max. The motor is around 20v so the flyback could be up to ~200v, albeit fleeting.

 

[static zap]

Youch , sounds like real back emf .
(all puncture wounds will be cauterized )
..Low resistance is punished..

 

[Deuce]

Youch , sounds like real back emf .
(all puncture wounds will be cauterized )
..Low resistance is punished..

To be honest it's been years I have experienced flyback. Work has made my hands hard and dry, not the best conductors. No wounds, it hit me straight in the bloody palm!

I assumed there was a sharp bit of plastic and it was just a scratch, so I examined it, and then dismissed it and continued. Then the second time I lost my patience lmao!!

Having played around with power since I was about a 5 years old, it feels slightly wrong that I now have a moderate fear of picking up the cordless vacuum