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EMI from electric shavers etc

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Sam Stones24/03/2020 22:06:04
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875 forum posts
326 photos

From Monday, I shall need to stay a sufficient distance from certain devices that radiate EMI.

In particular, this applies to my use of a mains-powered shaver, which occasionally produces smells akin to sparking electric motors (ozone? etc).

On the basis that testing the razor near an ‘off station’ AM radio setting indicates EMI, I’d like to discover if sufficient shielding could be achieved by wrapping a large proportion of the razor in aluminium foil, and perhaps covering that with cling film.

Is this a viable solution?

I’d appreciate any positive comments.

Growing a beard would not please SWAMBOcheeky

Thanking you in advance.

Sam

pgk pgk24/03/2020 22:09:44
2563 forum posts
293 photos

If using it from a bathroom shaver socket that may also contribute. Personally i favour a wet shave.

pgk

Martin Kyte24/03/2020 22:31:30
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2751 forum posts
48 photos

Can anyone remember what desperate Dan used for shaving?

I know it was something wierd but cannot remember what.

I do remember Burt Munroe (The World Fastest Indian fame) using a grinding wheel in an electric drill to do his big toenails.

Martin

Michael Gilligan24/03/2020 22:40:56
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20182 forum posts
1053 photos

Sam,

One of the most comprehensive documents I have seen comes from Boston Scientific: **LINK**

https://www.bostonscientific.com/content/dam/lifebeat-online/en/documents/BSC_Electromagnetic_Compatibility_Guide.pdf

The shaver is mentioned on page 10

[quote]

Use precautions: Maintain at least a 6 inch (15 cm) separation between the shaver and the implanted device. Avoid draping cord over implanted device.

[/quote]

This seems sensible ... But please do note the assumption at the top of the column.

MichaelG.

ChrisH24/03/2020 23:11:56
1018 forum posts
30 photos

Sorry - can't help, I come from a long line of wet shavers.

But I do remember the smell you mention from when I did try an electric shaver, many many moons ago, when I, and the world, was young. Put me off rather.

On the basis of a) having to avoid EMI and b) pleasing SWMBO, the second being by far the most important considering the need to get Shed Capex Spend passed in the future amongst other considerations, I'd change to wet shaving as the easy way out, no worries option, personally. Simples!

Remember KISS!

Chris

Sam Stones24/03/2020 23:25:38
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875 forum posts
326 photos

Many thanks for your very prompt and sensitive response Michael.

Being a rather thin-skinned specimen, and given little time for shaving during NS square bashing I went ‘all electric’. That was in ’56, so I’m pretty set in my ways.

Just read your post Chris - Thank you too.

I now realise that members who truly understand screening for EMI, may justifiably refrain from comment.

It was worth a try.laugh

Sam

Emgee25/03/2020 00:31:38
2425 forum posts
290 photos

Hi Sam

I think the problem is that nobody wants to give advice because of the possible poor outcome if they get it wrong, for me I am cautious on occasions and this is such a time.

Good luck with your search for some definitive information.

Emgee

Sam Stones25/03/2020 00:39:38
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875 forum posts
326 photos

Thanks Emgee. Yes, that occurred to me shortly after I posted.

If anyone tells me to "Keep your chin up", they might care to measure the distance from their neck to their collar bone. Mine's less than 15cm. devil

Sam

Edited By Sam Stones on 25/03/2020 00:40:24

Steviegtr25/03/2020 01:03:04
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2431 forum posts
336 photos

Is this the sort of shaver with a rotating motor , using carbon brushes like the old ones did. If so the smell is usually the brushes getting worn down. Then they arc, causing interference with electronics. Just keep calm & carry on. ZZZZZZZ.

Steve.

Sam Stones25/03/2020 01:33:36
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875 forum posts
326 photos

Yes Steve.

Never having taken it apart, I can imagine it having a segmented copper commutator and carbon brushes.

In the early days I used contact-less types where the armature rocked back and forth at mains frequency.

There was a perforated steel foil between skin and chopper blades. Then along came the various rotary heads.

Thanks for your post.

Keep safe,

Sam

Edited By Sam Stones on 25/03/2020 01:35:48

Steviegtr25/03/2020 01:40:35
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2431 forum posts
336 photos

Ha ha yes I remember them. One of them . The guy said I liked it that much I bought the company. Vibrating / oscillating magnet.

Steve.

Sam Stones25/03/2020 02:01:07
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875 forum posts
326 photos

Steve, it was Victor Kiam. I read his book back in the 80's.

Not only buying the Remington company, he used various ploys to gain easy access to ball games.

A fun read.

Sam

PS - I can see you're working late!

Steviegtr25/03/2020 03:28:20
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2431 forum posts
336 photos
Posted by Sam Stones on 25/03/2020 02:01:07:

Steve, it was Victor Kiam. I read his book back in the 80's.

Not only buying the Remington company, he used various ploys to gain easy access to ball games.

A fun read.

Sam

PS - I can see you're working late!

I always work late. Unfortunately I am a nocturnal person. Should have been born a cat.

Steve.

Hopper25/03/2020 03:34:44
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6383 forum posts
334 photos

Would it be safer to buy a new rechargeable battery shaver?

Braun brand have the oscillating head covered by a foil and seem to work ok.

Steviegtr25/03/2020 03:57:56
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2431 forum posts
336 photos
Posted by Hopper on 25/03/2020 03:34:44:

Would it be safer to buy a new rechargeable battery shaver?

Braun brand have the oscillating head covered by a foil and seem to work ok.

another late night cat.

Steve.

S.D.L.25/03/2020 06:55:20
236 forum posts
37 photos
Posted by Martin Kyte on 24/03/2020 22:31:30:

Can anyone remember what desperate Dan used for shaving?

Martin

Was he the one who hit them in with a hammer and chewed them off inside or was that an old song?🤔😀

Steve

pgk pgk25/03/2020 07:26:17
2563 forum posts
293 photos
Posted by Martin Kyte on 24/03/2020 22:31:30:

Can anyone remember what desperate Dan used for shaving?

I know it was something wierd but cannot remember what.

Blowlamp comes to mind and once shooting beard hairs off with a pistol??

pgk

Mike Poole25/03/2020 08:03:57
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Moderator
3335 forum posts
73 photos

Avoiding EMI is difficult, failure of the components that control EMI will often not result in the device no longer working. We are surrounded by devices that have the potential to radiate, switch mode power supplies are everywhere and PV solar panels have an inverter that on a sunny day could be working hard. Properly designed devices in good working order should comply with EMI regs but unfortunately some imported equipment is not compliant. Poor installation of things like inverters for your lathe and mill can also result in unwanted emissions, arc welders are obviously a device to avoid. The inverters for spot welding transformer control all carried a pacemaker warning so I would avoid a car factory tour if you were considering one. I am surprised you promote the electric shave as a time saver, in the washroom when camping I find my wet shave is done and dusted while the electric boys are still stood there mowing away.

Mike

Robert Atkinson 225/03/2020 08:19:41
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1207 forum posts
20 photos

Mains or battery shaver does not matter, they can both cause interference.
To answer the original question, wrapping the shaver in aluminium foil is not a reliable means of reducing intterference. This is mainly because it will not provide reliable contact, even with itself. It might even form a resonator making emission worse for specific frequencies or directions. Covering the razor with self adhesive copper foil, soldering all the seams and providing a ground connection would probably help, but without making measurements you cannot be sure.
An isssue with modern implantable medical devices is that many have a "remote control" capability sometimes with an antenna remote from the device. This makes them more vunerable to interference.
This is a classic case of safety probability / impact assessment. The probability of emissions causing problem is low (probably "extremly remote,10-7 in safety terms) but the effect is catastrophic (death) so additional precautions, keep emitters away from device) are required to bring the probabilty dowm to an acceptable level (<10-9).
Note that on another threads on VFDs I have commented on the need to fit proper EM/EMC filters. Your device is one reason for this so please take care aroung machines with electronic speed controls particuarly DIY set-ups.

Note that the interference drops with the square of the distance, doubling the distance reduces interference by 4, so knowing were the device an any antenna are would allow for a better judgement to be made. If they are in the neck/head then electric shaving is a no-no, if they are in the abomen then you could make a judgment call.

As a professional engineer involved in EMI/EMC I can only recommend you follow the advice given by the device manufacturer and your medical specialists.

Robert G8RPI.

Ed Duffner25/03/2020 08:45:17
840 forum posts
94 photos

If the motor requires cooling, wrapping the shaver might cause it to burn out. Simlarly, a number of the power tools, especially nibblers we have in for repair have the cooling vents closed off by the owners with silver duct tape, to prevent injestion of swarf. Some motors need to be cooled.

Ed.

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