Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.


--


Adam

On 07/04/2021 21:42, ARW wrote:
Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.

The DC voltage across the capacitor will be the same, the difference:
one way it will be referenced to neutral, ie close to ground, and the
other will have 230V superimposed on the capacitor terminals.

If an electrolytic capacitor then diode polarity will be very important.

What are you trying to do?

On 07/04/2021 21:46, Fredxx wrote:
On 07/04/2021 21:42, ARW wrote:
Am I correct in saying that it does not matter if there is a LN
reversal on the input?

It will always have a correct +/- DC voltage.

The DC voltage across the capacitor will be the same, the difference:
one way it will be referenced to neutral, ie close to ground, and the
other will have 230V superimposed on the capacitor terminals.

I'd assumed Adam meant a bridge rectifier as in

https://www.electronics-tutorials.ws...?fit=331%2C191

but I am prone to be wrong

--
Robin
reply-to address is (intended to be) valid

ARW wrote

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.

Correct, its the diode config that determines the +/- DC voltage.

"Fredxx" wrote in message
...
On 07/04/2021 21:42, ARW wrote:
Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.

The DC voltage across the capacitor will be the same,

Yes.

the difference: one way it will be referenced to neutral, ie close to
ground, and the other will have 230V superimposed on the capacitor
terminals.

Nope, even with a device with no earth connection.

If an electrolytic capacitor then diode polarity will be very important.

What are you trying to do?

On Thu, 8 Apr 2021 07:15:31 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:


FLUSH the trolling senile asshole's latest troll**** unread

--
Website (from 2007) dedicated to the 86-year-old senile Australian
cretin's pathological trolling:
https://www.pcreview.co.uk/threads/r...d-faq.2973853/

On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 07/04/2021 22:12, Robin wrote:
On 07/04/2021 21:46, Fredxx wrote:
On 07/04/2021 21:42, ARW wrote:
Am I correct in saying that it does not matter if there is a LN
reversal on the input?

It will always have a correct +/- DC voltage.

The DC voltage across the capacitor will be the same, the difference:
one way it will be referenced to neutral, ie close to ground, and the
other will have 230V superimposed on the capacitor terminals.

I'd assumed Adam meant a bridge rectifier as in

https://www.electronics-tutorials.ws...?fit=331%2C191


but I am prone to be wrong

I saw "full wave rectifier" and thought "single diode". My bad, I should
try reading a little harder.

In which case L-N reversal will make no difference.

Your link is spot on.

On Wed, 7 Apr 2021 23:46:23 +0100, John Rumm
wrote:

On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.

I did that with a piece of battery powered kit I used to build to go
with my guitars. It used an off-the-shelf box with built-in battery
connectors that didn't have anything physical to prevent you putting
in the battery the wrong way round. Rather than use a (much) more
expensive box, I added a bridge rectifier into the circuit. Belt.
Braces. Piece of string in pocket.


Nick

On 07/04/2021 21:42, ARW wrote:
Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.



Correct.

PA

On 08/04/2021 09:30, Jeff Layman wrote:
On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.

Surely you only need a single rectifier connected the right way round in
either the +ve or -ve line. With a bridge rectifier three of the diodes
are effectively redundant (unless one goes short-circuit), and you've
got a double voltage drop across the diodes to take into account. That
might be significant for the equipment - a bit like trying to use NiCads
instead of alkaline-manganese batteries.

Even if you're trying to cater for the extremely rare short-circuit
mentioned above, you still only need two diodes.


A single diode only passes 50% of the mains, a bridge of a full-wave
passes 100% - so less ripple on the output - or a cheaper capacitor results.

PA

On 08/04/2021 09:30, Jeff Layman wrote:
On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.

Surely you only need a single rectifier connected the right way round in
either the +ve or -ve line. With a bridge rectifier three of the diodes
are effectively redundant (unless one goes short-circuit), and you've
got a double voltage drop across the diodes to take into account. That
might be significant for the equipment - a bit like trying to use NiCads
instead of alkaline-manganese batteries.

Even if you're trying to cater for the extremely rare short-circuit
mentioned above, you still only need two diodes.


A single diode only passes 50% of the mains, a bridge or a full-wave
passes 100% - so less ripple on the output - or a cheaper capacitor results.

PA

On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.

Surely you only need a single rectifier connected the right way round in
either the +ve or -ve line. With a bridge rectifier three of the diodes
are effectively redundant (unless one goes short-circuit), and you've
got a double voltage drop across the diodes to take into account. That
might be significant for the equipment - a bit like trying to use NiCads
instead of alkaline-manganese batteries.

Even if you're trying to cater for the extremely rare short-circuit
mentioned above, you still only need two diodes.

--

Jeff

On 8 Apr 2021 at 09:30:47 BST, "Jeff Layman"
wrote:

On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.

Surely you only need a single rectifier connected the right way round in
either the +ve or -ve line. With a bridge rectifier three of the diodes
are effectively redundant (unless one goes short-circuit), and you've
got a double voltage drop across the diodes to take into account. That
might be significant for the equipment - a bit like trying to use NiCads
instead of alkaline-manganese batteries.

Even if you're trying to cater for the extremely rare short-circuit
mentioned above, you still only need two diodes.

But with a bridge it works whichever way round you put the battery. Not that
it is usually worth it.

--
Roger Hayter

Jeff Layman wrote:

John Rumm wrote:

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.

Surely you only need a single rectifier connected the right way round in
either the +ve or -ve line. With a bridge rectifier three of the diodes
are effectively redundant (unless one goes short-circuit), and you've
got a double voltage drop across the diodes to take into account. That
might be significant for the equipment - a bit like trying to use NiCads
instead of alkaline-manganese batteries.

If you want reverse voltage protection, while minimizing voltage drop, a
P-channel FET is better, maybe with a zener to protect the FET from a
reverse voltage that is also too high e.g.

https://components101.com/asset/sites/default/files/inline-images/PMOS-Reverse-Polarity-Protection-Circuit.png

On 08/04/2021 09:59, Roger Hayter wrote:
On 8 Apr 2021 at 09:30:47 BST, "Jeff Layman"
wrote:

On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.

Surely you only need a single rectifier connected the right way round in
either the +ve or -ve line. With a bridge rectifier three of the diodes
are effectively redundant (unless one goes short-circuit), and you've
got a double voltage drop across the diodes to take into account. That
might be significant for the equipment - a bit like trying to use NiCads
instead of alkaline-manganese batteries.

Even if you're trying to cater for the extremely rare short-circuit
mentioned above, you still only need two diodes.

But with a bridge it works whichever way round you put the battery. Not that
it is usually worth it.


If you do use a full wave bridge rectifier, there will be a total
voltage drop of 1.2 V across the rectifier.

There will be a maximum current rating for the diodes and not only that,
once you use P=VI, you may find in high current applications you may
need to heatsink the rectifier to dissipate the power across it to keep
it within its SOA (Safe operating area)

Some high current rated rectifiers have an electrically isolated metal
case with a hole drilled through it for mounting to a heat sink.

like this example:
https://www.rapidonline.com/Electron...-400V-50-0262/

Also, keep an eye on the peak reverse voltage limit on the diodes. if on
220 AC mains, thats in rms, the peak voltage is nearer 320 V.

Similarly, if using a smoothing capacitor across rectified mains, you'd
need a 400 V rated one.....

"Jeff Layman" wrote in message
...
On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.

Surely you only need a single rectifier connected the right way round in
either the +ve or -ve line.

Yes.

With a bridge rectifier three of the diodes are effectively redundant
(unless one goes short-circuit),

Nope, they allow the device to work regardless of how its powered.

and you've got a double voltage drop across the diodes to take into
account. That might be significant for the equipment - a bit like trying
to use NiCads instead of alkaline-manganese batteries.

Even if you're trying to cater for the extremely rare short-circuit
mentioned above, you still only need two diodes.

Yes.

On 08/04/2021 08:48, Peter Able wrote:
On 08/04/2021 09:30, Jeff Layman wrote:
On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN
reversal
on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.

Surely you only need a single rectifier connected the right way round
in either the +ve or -ve line. With a bridge rectifier three of the
diodes are effectively redundant (unless one goes short-circuit), and
you've got a double voltage drop across the diodes to take into
account. That might be significant for the equipment - a bit like
trying to use NiCads instead of alkaline-manganese batteries.

Even if you're trying to cater for the extremely rare short-circuit
mentioned above, you still only need two diodes.


A single diode only passes 50% of the mains, a bridge or a full-wave
passes 100% - so less ripple on the output - or a cheaper capacitor
results.


It's not always mains AC. Sometimes an appliance provides something like
24v ac output for peripheral devices, like a remote transceiver, or a
home automation device.

After rectification you may need to also reduce the voltage with
something like a voltage regulator. Which AIUI is basically resistance
and hence power inefficient.

The question I had is might a half wave rectifier be better (than a full
wave rectifier) to convert 24v ac to 5v dc, i.e give the resistance less
work.

In the end I gave up and decided it was better to use a USB wall plug
transformer, but it was something I have pondered upon since.

On Thu, 8 Apr 2021 19:31:12 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:


FLUSH the trolling senile asshole's latest troll**** unread

--
"Who or What is Rod Speed?
Rod Speed is an entirely modern phenomenon. Essentially, Rod Speed
is an insecure and worthless individual who has discovered he can
enhance his own self-esteem in his own eyes by playing "the big, hard
man" on the InterNet."
https://www.pcreview.co.uk/threads/r...d-faq.2973853/

On Thu, 08 Apr 2021 10:52:17 +0100, Pancho wrote:

On 08/04/2021 08:48, Peter Able wrote:
On 08/04/2021 09:30, Jeff Layman wrote:
On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN
reversal on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an
external supply, then sticking a bridge rectifier on the input even
though you are only ever expecting DC rather than AC, is a way to
ensure your kit will never see the input polarity reversed if used
with the wrong PSU.

Surely you only need a single rectifier connected the right way round
in either the +ve or -ve line. With a bridge rectifier three of the
diodes are effectively redundant (unless one goes short-circuit), and
you've got a double voltage drop across the diodes to take into
account. That might be significant for the equipment - a bit like
trying to use NiCads instead of alkaline-manganese batteries.

Even if you're trying to cater for the extremely rare short-circuit
mentioned above, you still only need two diodes.


A single diode only passes 50% of the mains, a bridge or a full-wave
passes 100% - so less ripple on the output - or a cheaper capacitor
results.


It's not always mains AC. Sometimes an appliance provides something like
24v ac output for peripheral devices, like a remote transceiver, or a
home automation device.

After rectification you may need to also reduce the voltage with
something like a voltage regulator. Which AIUI is basically resistance
and hence power inefficient.

The question I had is might a half wave rectifier be better (than a full
wave rectifier) to convert 24v ac to 5v dc, i.e give the resistance less
work.

In the end I gave up and decided it was better to use a USB wall plug
transformer, but it was something I have pondered upon since.

Switch mode regulator can be a pulse width modulated output for 90%
efficiency.

On 08/04/2021 08:45, Peter Able wrote:
On 08/04/2021 09:30, Jeff Layman wrote:
On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.

Surely you only need a single rectifier connected the right way round in
either the +ve or -ve line. With a bridge rectifier three of the diodes
are effectively redundant (unless one goes short-circuit), and you've
got a double voltage drop across the diodes to take into account. That
might be significant for the equipment - a bit like trying to use NiCads
instead of alkaline-manganese batteries.

Even if you're trying to cater for the extremely rare short-circuit
mentioned above, you still only need two diodes.


A single diode only passes 50% of the mains, a bridge of a full-wave
passes 100% - so less ripple on the output - or a cheaper capacitor results.

I was replying to John's point about protection from a reversed-polarity
DC supply. In that case we are not concerned with ripple, etc - purely
the problem of connecting the DC +ve of the supply to the -ve of the
equipment. That could be due, for example, to a coaxial plug with a
low-voltage DC supply having the reverse connection to the inner and
outer from the usual power supply plug.

--

Jeff

On 08/04/2021 09:59, Roger Hayter wrote:
On 8 Apr 2021 at 09:30:47 BST, "Jeff Layman"
wrote:

On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.

Surely you only need a single rectifier connected the right way round in
either the +ve or -ve line. With a bridge rectifier three of the diodes
are effectively redundant (unless one goes short-circuit), and you've
got a double voltage drop across the diodes to take into account. That
might be significant for the equipment - a bit like trying to use NiCads
instead of alkaline-manganese batteries.

Even if you're trying to cater for the extremely rare short-circuit
mentioned above, you still only need two diodes.

But with a bridge it works whichever way round you put the battery. Not that
it is usually worth it.

That is true, but although it might be convenient, it wasn't the point I
was trying to make in relation to equipment protection against a
reverse-polarity power supply.

I think that it might be used by decent manufacturers of quality
equipment, where the cost of a few extra diodes in a bridge (pennies)
would make little difference to the bottom line, and should be good PR.

--

Jeff

ARW presented the following explanation :
Am I correct in saying that it does not matter if there is a LN reversal on
the input?

It will always have a correct +/- DC voltage.

You are correct!

In article ,
ARW wrote:
Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.

Assuming the AC is coming from an isolating transformer, no practical
difference at all.

--
*I'm out of my mind, but feel free to leave a message.

Dave Plowman London SW
To e-mail, change noise into sound.

On 08/04/2021 10:52, Pancho wrote:
On 08/04/2021 08:48, Peter Able wrote:
On 08/04/2021 09:30, Jeff Layman wrote:
On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN
reversal
on the input?

Surely you only need a single rectifier connected the right way round
in either the +ve or -ve line. With a bridge rectifier three of the
diodes are effectively redundant (unless one goes short-circuit), and
you've got a double voltage drop across the diodes to take into
account. That might be significant for the equipment - a bit like
trying to use NiCads instead of alkaline-manganese batteries.

A single diode only passes 50% of the mains, a bridge or a full-wave
passes 100% - so less ripple on the output - or a cheaper capacitor
results.


It's not always mains AC. Sometimes an appliance provides something like
24v ac output for peripheral devices, like a remote transceiver, or a
home automation device.

After rectification you may need to also reduce the voltage with
something like a voltage regulator. Which AIUI is basically resistance
and hence power inefficient.

The question I had is might a half wave rectifier be better (than a full
wave rectifier) to convert 24v ac to 5v dc, i.e give the resistance less
work.

In the end I gave up and decided it was better to use a USB wall plug
transformer, but it was something I have pondered upon since.

The OP mentions "LN reversal" so this thread is about mains. He also
mentions a "smoothing capacitor" - so it is AC Mains he is asking about.

So, your reply is OT - but that's OK.

Wall plug USB PSUs are so cheap, you've made the right choice.

PA

It will remain the same polarity if you feed dc into the input if that is
what you are asking, it will be the volts in minus the .6v in each
conducting diode one assumes, indeed if you are using dc and only using the
bridge so you can connect any old dc any way around, you don't need the
capacitor at all.
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"ARW" wrote in message
...
Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.


--


Adam

Yes I was confused as normally one would use an isolating transformer in
such a case. Also if you are inputting ac, the hum you hear will be 100 hz
not 50hz.

I cannot think of any safe usage for this idea connected straight to the
mains other than making your own electric execution chair perhaps.
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Fredxx" wrote in message
...
On 07/04/2021 21:42, ARW wrote:
Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.

The DC voltage across the capacitor will be the same, the difference: one
way it will be referenced to neutral, ie close to ground, and the other
will have 230V superimposed on the capacitor terminals.

If an electrolytic capacitor then diode polarity will be very important.

What are you trying to do?

On 08/04/2021 09:30, Jeff Layman wrote:
On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.

Surely you only need a single rectifier connected the right way round in
either the +ve or -ve line. With a bridge rectifier three of the diodes
are effectively redundant (unless one goes short-circuit), and you've
got a double voltage drop across the diodes to take into account. That
might be significant for the equipment - a bit like trying to use NiCads
instead of alkaline-manganese batteries.

Even if you're trying to cater for the extremely rare short-circuit
mentioned above, you still only need two diodes.

One diode will give input protection, but with the supply polarity
reversed, the device won't work.

With a bridge, then it will work regardless of the polarity of the
supply. Generally if using an unregulated supply with internal
regulation, the supply voltage will have enough headroom to allow for a
couple of diode junction drops.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 07/04/2021 23:46, John Rumm wrote:
On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN
reversal on the input?

Correct...

It will always have a correct +/- DC voltage.

Yup.

In fact if you are designing DC powered kit that runs from an external
supply, then sticking a bridge rectifier on the input even though you
are only ever expecting DC rather than AC, is a way to ensure your kit
will never see the input polarity reversed if used with the wrong PSU.



Same applies to data. The Army's FAM - Field Alert Monitor - starts with
a bridge.

Squaddy-proof !

PA

On 08/04/2021 01:04, Fredxx wrote:
On 07/04/2021 22:12, Robin wrote:
On 07/04/2021 21:46, Fredxx wrote:
On 07/04/2021 21:42, ARW wrote:
Am I correct in saying that it does not matter if there is a LN
reversal on the input?

It will always have a correct +/- DC voltage.

The DC voltage across the capacitor will be the same, the difference:
one way it will be referenced to neutral, ie close to ground, and the
other will have 230V superimposed on the capacitor terminals.

I'd assumed Adam meant a bridge rectifier as in

https://www.electronics-tutorials.ws...?fit=331%2C191


but I am prone to be wrong

I saw "full wave rectifier" and thought "single diode". My bad, I should
try reading a little harder.

In which case L-N reversal will make no difference.

Your link is spot on.



And the reason I posted is because I found a LN reversal on a socket
during a EICR.

The tenant was adamant a rectifier would not work.

I was convinced it would (even after a bottle wine of when I posted).

So I asked the collective wisdom of you fine posters.

--
Adam

Brian Gaff (Sofa) wrote

It will remain the same polarity if you feed dc into the input if that is
what you are asking,

It cant be because he specifically mentions active
and neutral, so must be talking about the AC mains.

it will be the volts in minus the .6v in each conducting diode one
assumes, indeed if you are using dc and only using the bridge so you can
connect any old dc any way around, you don't need the capacitor at all.

"ARW" wrote in message
...
Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.


--


Adam

On Fri, 9 Apr 2021 03:25:33 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:


It will remain the same polarity if you feed dc into the input if that is
what you are asking,

It cant be

Always happy to auto-contradict, eh, senile cretin? LOL

--
"Who or What is Rod Speed?
Rod Speed is an entirely modern phenomenon. Essentially, Rod Speed
is an insecure and worthless individual who has discovered he can
enhance his own self-esteem in his own eyes by playing "the big, hard
man" on the InterNet."
https://www.pcreview.co.uk/threads/r...d-faq.2973853/

On 7 Apr 2021 at 21:42:19 BST, "ARW" wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.

Yes, but obviously with an earthed public supply a full wave rectifier
implies that neither + or _ terminal are anywhere near earth DC potential (and
approx equally distant from it). Of course, as the live input is at the same
*average* potential as neutral it is not going to make a difference to the DC
output level which way round you connect the supply.

--
Roger Hayter

On 08/04/2021 20:33, Roger Hayter wrote:
On 7 Apr 2021 at 21:42:19 BST, "ARW" wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.

Yes, but obviously with an earthed public supply a full wave rectifier
implies that neither + or _ terminal are anywhere near earth DC potential (and
approx equally distant from it). Of course, as the live input is at the same
*average* potential as neutral it is not going to make a difference to the DC
output level which way round you connect the supply.



It also depends on where the protective devices are and where there L-N
reversal is....

If the protective device is in the 13A plug on in the consumer unit
before where the L-N reversal happens then no practical safety issue as
its the L that gets switched off and in a PME earthed house, N will be
close to the same potential as the CPC.

However, if the L-N reversal is BEFORE the protective device, then the N
gets cut anbd you still have a Live L with a potential od 220 V AC RMS
relative to the CPC......

On 08/04/2021 17:55, ARW wrote:
On 08/04/2021 01:04, Fredxx wrote:
On 07/04/2021 22:12, Robin wrote:
On 07/04/2021 21:46, Fredxx wrote:
On 07/04/2021 21:42, ARW wrote:
Am I correct in saying that it does not matter if there is a LN
reversal on the input?

It will always have a correct +/- DC voltage.

The DC voltage across the capacitor will be the same, the
difference: one way it will be referenced to neutral, ie close to
ground, and the other will have 230V superimposed on the capacitor
terminals.

I'd assumed Adam meant a bridge rectifier as in

https://www.electronics-tutorials.ws...?fit=331%2C191


but I am prone to be wrong

I saw "full wave rectifier" and thought "single diode". My bad, I
should try reading a little harder.

In which case L-N reversal will make no difference.

Your link is spot on.

And the reason I posted is because I found a LN reversal on a socket
during a EICR.

The tenant was adamant a rectifier would not work.

I was convinced it would (even after a bottle wine of when I posted).

So I asked the collective wisdom of you fine posters.

He clearly doesn't understand what AC stands for, and/or what a
rectifier does.

--
Max Demian

On Wed, 7 Apr 2021 21:46:42 +0100, Fredxx wrote:


On 07/04/2021 21:42, ARW wrote:

Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.


The DC voltage across the capacitor will be the same, the difference:
one way it will be referenced to neutral, ie close to ground, and the
other will have 230V superimposed on the capacitor terminals.

If an electrolytic capacitor then diode polarity will be very important.

What are you trying to do?


Being relevant to the thread about Free Agent losing posts, why
haven't I got ARW's original "Full wave rectifier with a smoothing
capacitor"?
--
Dave W

"Dave W" wrote in message
...
On Wed, 7 Apr 2021 21:46:42 +0100, Fredxx wrote:

On 07/04/2021 21:42, ARW wrote:
Am I correct in saying that it does not matter if there is a LN reversal
on the input?

It will always have a correct +/- DC voltage.

The DC voltage across the capacitor will be the same, the difference:
one way it will be referenced to neutral, ie close to ground, and the
other will have 230V superimposed on the capacitor terminals.

If an electrolytic capacitor then diode polarity will be very important.

What are you trying to do?

Being relevant to the thread about Free Agent losing posts, why
haven't I got ARW's original "Full wave rectifier with a smoothing
capacitor"?

Because Free Agent or your usenet server is ****ed.

Certainly Free Agent in your case.

On 08/04/2021 15:49, Peter Able wrote:


The OP mentions "LN reversal" so this thread is about mains. He also
mentions a "smoothing capacitor" - so it is AC Mains he is asking about.


Why does that mean AC Mains, as opposed to any AC rectification?

On Fri, 9 Apr 2021 08:45:02 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:



Because Free Agent or your usenet server is ****ed.

Post proof, senile cretin!

Certainly Free Agent in your case.

Post proof, you endlessly bull****ting trolling piece of senile ****!

--
pamela about Rodent Speed:
"His off the cuff expertise demonstrates how little he knows..."
MID:

On 09/04/2021 08:21, Pancho wrote:
On 08/04/2021 15:49, Peter Able wrote:


The OP mentions "LN reversal" so this thread is about mains. He also
mentions a "smoothing capacitor" - so it is AC Mains he is asking about.


Why does that mean AC Mains, as opposed to any AC rectification?



If it were DC mains or a battery he's far less likely to have mentioned
a smoothing capacitor - hence my guess that he's talking about AC Mains.
And I remember DC Mains !

"AC rectification" is a process, "AC mains" is an input to that process.
So they are different things - like petrol is to cars.

In this case AC mains is rectified, delivering only pulses of DC voltage
of one polarity. In the case of DC mains/batteries, the process of
rectification is virtually invisible, - DC in, DC out.

Half-wave rectification is accomplished using a single diode. The snag
is that one of the two mains input wires passes through the process. Get
that the wrong way around and what was thought to be the GROUND of the
TV chassis is actually at LINE voltage. Been a service engineer - got
the scars - still.

Bridge rectification is, effectively a switch being flipped 100 times a
second. Thus the output is always pulses of the same polarity - and
twice as many as for the half-wave. There's still the problem, though,
that neither of the outputs is safe to touch! Bridge rectification has
been known of for some time - but the cost of thermionic diodes was so
high, once upon a time, that it generally didn't catch on. These days
semiconductor bridges are so cheap - that's the way to go.

Isolating the Rectifier from the mains - i.e. making things safer - was
generally accepted to require an isolation transformer ahead of the
rectifier. At one time, these transformers were expensive. Now they
aren't - so some simple PSUs nowadays contain one. Some geezer came up
with the idea of having two identical output windings on the
transformer. You could then connect these windings in a way that one was
always delivering the mirror image of the other. This meant that when
one winding was offering a positive pulse the other would be offering a
negative - and vice versa. That cuts the number of diodes required from
4 to 2 in order to achieve full-wave rectification. That was a big
saving in terms of the cost thermionic diodes - but - cheap
semiconductor diodes have blown that option out of the water. No option
to have a DC input..... Until....

Modern power supplies take all of those ideas and shake them all up.
They start with a bridge rectifier, then a smoothing capacitor. The
resulting ripply DC is chopped into a transformer at about 100kHz by a
simple oscillator. The outputs of one or more of the post-transformer
rectifiers (usually half-waye) is fed back to the chopper to stabilise
the output voltages and this signal is the only thing that connects the
pre-tranformer circuitry to the post-transformer circuitry - usually,
nowadays, by means of an optical isolator, So the risk of electric
shock is gone. Open up an old PC PSU and you'll clearly see the Berlin
Wall nature of the isolation of one group of PCB tracks from the others !

E&OE !

PA