Detect polarisation for unpolarised mains.

Thread Starter

JunkieNL

Joined Mar 19, 2020
45
Hello,

I have bought a great value for money CNC spindle on AliExpress. Unfortunately the power supply is not isolated from mains. Since our European (Schuko) plugs are not polarised, a tossing of the coin of fate determines if the power supply is referenced to live or neutral. I will ground both the power supply enclosure and the spindle, but I also want to add a telltale for the aforementioned coin toss.

Would this work and be an acceptable solution:
1638121243827.png

-The HLK-5M05 is an isolated power supply, 230V AC to 5V DC, 5W.
-The B0505S is a 5V DC to 5V DC isolator, 1W.
-The load measures voltage, current and rpm of the spindle and is referenced to either A or B.

If it works as I intended, then the LED should only be lit when A is connected to live.
 

LowQCab

Joined Nov 6, 2012
1,619
It would be a MUCH better idea to simply replace both the Socket and the Plug with Polarized items.
I'm sure that they must be available where You live,
and, it would probably cost less, and be safer than, what You are proposing.

Then it would simply be a matter of measuring each Wire to Ground,
and wiring the new Outlet and Plug appropriately.

On any Metallic Machine,
there should be a good, separate, connection to Ground attached to the Frame/Chassis,
that DOES NOT carry any Current under normal conditions.
You should have a minimum of 3-Wires, Hot, Neutral, and Ground.

I thought the US was the last place to have un-polarized-Power-Outlets,
I would guess that ~95% of them have since been replaced with Polarized-Outlets.
.
.
.
 

Thread Starter

JunkieNL

Joined Mar 19, 2020
45
It would be a MUCH better idea to simply replace both the Socket and the Plug with Polarized items.
I'm sure that they must be available where You live,
and, it would probably cost less, and be safer than, what You are proposing.

Then it would simply be a matter of measuring each Wire to Ground,
and wiring the new Outlet and Plug appropriately.

On any Metallic Machine,
there should be a good, separate, connection to Ground attached to the Frame/Chassis,
that DOES NOT carry any Current under normal conditions.
You should have a minimum of 3-Wires, Hot, Neutral, and Ground.

I thought the US was the last place to have un-polarized-Power-Outlets,
I would guess that ~95% of them have since been replaced with Polarized-Outlets.
.
.
.
Polarised plugs and sockets are not available in stores in The Netherlands or Germany. You can't buy them and I am pretty sure building regulations wouldn't allow installing them in my home. All new houses come with these sockets:
1638135983321.png
They are very safe. No one dares to stick metal objects in either hole, because you don't know which one is 230 V.
 

LowQCab

Joined Nov 6, 2012
1,619
They're not very "safe" if You can plug them in up-side-down,
but at least it appears that there is a dedicated Ground Connection,
or is that a simple spring-metal-retaining-clip, and not really Grounded ?

Here's what they look like in the US.
15-Amp rated Left, and 20-Amp rated right.
( without Trim-Plates )
.
.
.
Outlets .png
 

Ian0

Joined Aug 7, 2020
4,146
Live and neutral are both considered as "live". If either is connected to earth, or can be touched the item should not be used. The only safe option is to use a mains isolating transformer.
 

Thread Starter

JunkieNL

Joined Mar 19, 2020
45
Live and neutral are both considered as "live". If either is connected to earth, or can be touched the item should not be used. The only safe option is to use a mains isolating transformer.
After putting the power supply in an enclosure, live and neutral cannot be touched. The metal parts that can be touched (enclosure and spindle) will be connected to ground. All sockets are protected with a circuit breaker that trips if more than 30 mA leaks to the earth. I think that is pretty safe, although I would have preferred an isolated supply. The proposed circuit leaks 0,1 mA to earth. Maybe I could even lower that by a factor of 10.
 
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