Electric shock from coffee grinder

[Andrew]

My wife is getting electric shocks from the coffee grinder... when it's unplugged and she's putting it away. She touches the plug pins and 'zap'.... and it's not static either. It's never happened to me, but then I'm a bloke and never put things away.

My extremely limited knowledge of electrics suggests it is possible, since I know capacitors (for instance) store energy and do discharge but I've no idea if a simple coffee grinder would contain such wizzardry.

I've found others on the interweb saying they get similar shocks,  so my question is how? My guess is capacitor discharge but it is a total guess!

[tiermat]

Sounds like it.  Certain electrical gadgets have capacitors across the AC lines to smooth the input.  Obviously they are still live when unplugged (still charged up).

[mrcharly-YHT]

Doesn't have to be capacitors, other devices can store surprising amounts.


If the grinder isn't earthed, it could be that the whole grinder is acting as a capacitor.

[Andrew]

If the grinder isn't earthed, it could be that the whole grinder is acting as a capacitor.

Blimey, I didn't know that. Cheers.

As I say, I don't recall ever having had such a shock, from any device. And if I have, I've probably dismissed it as static. You live and learn eh?

[Rhys W]

Could be an earthing problem caused by a two-wire mains lead, and the plug's earth pin is not connected to anything. A DC motor is going to have sizeable capacitors associated with it, and they might not have a good path to earth to discharge them.

[hellymedic]

I know the OP says it's not static, but I wonder if grinding up dry coffee beans of itself could build up quite a static charge.

[Wobbly John]

Simplest solution is to get into the habit of touching the pins of the plug onto something metal each time it's unpluged.

I've experienced shocks off tellys through the plugs (capacitors) and fracmo dc motors (not capacitor) some mains motors have a starter capacitor, but I don't  understand it well enough to know if this is the source of the charge.

[Toady]

Switch it on after unplugging it.  There's obviously a bit of electricity left in the pipe, that should use it all up.

[Andrew]

Switch it on after unplugging it.  There's obviously a bit of electricity left in the pipe, that should use it all up.

A variation of that is do-able; that is, unplug it whilst it's still running.

[Ham]

I had a stick blender with the same problem, I used Wobbly's suggestion of shorting the pins before deciding that 25 years was probably enough and changed it.

[Jurek]

Simplest solution is to get into the habit of touching the pins of the plug onto something metal each time it's unpluged.

I've experienced shocks off tellys through the plugs (capacitors) and fracmo dc motors (not capacitor) some mains motors have a starter capacitor, but I don't  understand it well enough to know if this is the source of the charge.

^
This.
I experience the same thing from my Dremel.
It didn't take too many recurrences to get me into the habit of shorting out the plug pins on something conductive.
Nice crack of a dry spark adds to the Van Der Graaff effect.

[tonycollinet]

It could be the motor start capacitor. Does the grinder have an on/off switch - if so, switching off before unplugging should isolate the capacitor IF it is the start capacitor.