HT Relay

[Ian Bell[_2_]]

I am trying to select a relay for a delayed HT switch (which will also
discharge the HT when off). Most relays I can find have contacts rated
at 250VAC which translates into a peak of about 350V. However, data is
scarce on what dc voltage these relays can switch. So far I have found
only one that gives a dc current versus voltage curve and that stops at
210V dc (and 200mA) and I really want to be able to switch up to 350V at
up to 200mA. The rest just give a dc voltage at max current value.

So, I am guessing that this problem has been faced before and there are
relays that are known to work fine in this application. Any recommendations?

By the way I prefer a 5V coil.

Cheers

Ian

[Phil Allison[_3_]]

"Ian Bell"

>I am trying to select a relay for a delayed HT switch (which will also
>discharge the HT when off). Most relays I can find have contacts rated at
>250VAC which translates into a peak of about 350V. However, data is scarce
>on what dc voltage these relays can switch. So far I have found only one
>that gives a dc current versus voltage curve and that stops at 210V dc (and
>200mA) and I really want to be able to switch up to 350V at up to 200mA.
>The rest just give a dc voltage at max current value.
>
> So, I am guessing that this problem has been faced before and there are
> relays that are known to work fine in this application. Any
> recommendations?



** Relay contacts are rated in *BREAKING* capacity - you IDIOT.

You seem to only need the relay to *MAKE* a DC circuit - so no issue exists
at all.

Play safe - and switch the ****ing AC.

IMBECILE !!



..... Phil

[Ian Bell[_2_]]

Phil Allison wrote:
> "Ian Bell"
>
>> I am trying to select a relay for a delayed HT switch (which will also
>> discharge the HT when off). Most relays I can find have contacts rated at
>> 250VAC which translates into a peak of about 350V. However, data is scarce
>> on what dc voltage these relays can switch. So far I have found only one
>> that gives a dc current versus voltage curve and that stops at 210V dc (and
>> 200mA) and I really want to be able to switch up to 350V at up to 200mA.
>> The rest just give a dc voltage at max current value.
>>
>> So, I am guessing that this problem has been faced before and there are
>> relays that are known to work fine in this application. Any
>> recommendations?
>
>
>
> ** Relay contacts are rated in *BREAKING* capacity - you IDIOT.
>
> You seem to only need the relay to *MAKE* a DC circuit - so no issue exists
> at all.
>

No, I need it to break it too - note the bit about discharging when HT
is off - it needs to break the normal load and make the discharge load (
and vice versa)


> Play safe - and switch the ****ing AC.

Are you suggesting I switch the ac secondary?

Cheers

Ian
>
> IMBECILE !!
>
>
>
> .... Phil
>
>
>
>
>

[Arny Krueger]

"Ian Bell" > wrote in message

> I am trying to select a relay for a delayed HT switch
> (which will also discharge the HT when off). Most relays
> I can find have contacts rated at 250VAC which translates into a peak of
> about 350V.
> However, data is scarce on what dc voltage these relays
> can switch. So far I have found only one that gives a dc current versus
> voltage curve and
> that stops at 210V dc (and 200mA) and I really want to be
> able to switch up to 350V at up to 200mA. The rest just give a dc voltage
> at max
> current value.
> So, I am guessing that this problem has been faced before
> and there are relays that are known to work fine in this
> application. Any recommendations?
> By the way I prefer a 5V coil.
>

Deepending on your application, couldn't you implement the switch
electronically with a series tube, perhaps even a thyratron?

[Phil Allison[_3_]]

"Ian Bell"
Phil Allison wrote:
>
>>> I am trying to select a relay for a delayed HT switch (which will also
>>> discharge the HT when off). Most relays I can find have contacts rated
>>> at 250VAC which translates into a peak of about 350V. However, data is
>>> scarce on what dc voltage these relays can switch. So far I have found
>>> only one that gives a dc current versus voltage curve and that stops at
>>> 210V dc (and 200mA) and I really want to be able to switch up to 350V at
>>> up to 200mA. The rest just give a dc voltage at max current value.
>>>
>>> So, I am guessing that this problem has been faced before and there are
>>> relays that are known to work fine in this application. Any
>>> recommendations?
>>
>>
>>
>> ** Relay contacts are rated in *BREAKING* capacity - you IDIOT.
>>
>> You seem to only need the relay to *MAKE* a DC circuit - so no issue
>> exists at all.
>>
>
> No, I need it to break it too - note the bit about discharging when HT is
> off - it needs to break the normal load and make the discharge load ( and
> vice versa)


** Post a schematic - you IDIOT.

Still sounds like you are NOT breaking anything like 350 volts.



..... Phil

[Ian Bell[_2_]]

Phil Allison wrote:
> "Ian Bell"
> Phil Allison wrote:
>>>> I am trying to select a relay for a delayed HT switch (which will also
>>>> discharge the HT when off). Most relays I can find have contacts rated
>>>> at 250VAC which translates into a peak of about 350V. However, data is
>>>> scarce on what dc voltage these relays can switch. So far I have found
>>>> only one that gives a dc current versus voltage curve and that stops at
>>>> 210V dc (and 200mA) and I really want to be able to switch up to 350V at
>>>> up to 200mA. The rest just give a dc voltage at max current value.
>>>>
>>>> So, I am guessing that this problem has been faced before and there are
>>>> relays that are known to work fine in this application. Any
>>>> recommendations?
>>>
>>>
>>> ** Relay contacts are rated in *BREAKING* capacity - you IDIOT.
>>>
>>> You seem to only need the relay to *MAKE* a DC circuit - so no issue
>>> exists at all.
>>>
>> No, I need it to break it too - note the bit about discharging when HT is
>> off - it needs to break the normal load and make the discharge load ( and
>> vice versa)
>
>
> ** Post a schematic - you IDIOT.
>
> Still sounds like you are NOT breaking anything like 350 volts.
>

It is easy enough to describe. The relay common is connected to the HT
supply (semiconductor rectifiers and RC smoothing). The NC contact is
connected to ground via a resistor which is used to discharge the HT
supply caps when power is turned off. The NO contact goes to the circuit
to be powered by the supply. On power up the heater supply comes up
right away but the relay is held off for say 30 secs. Then the relay is
switched and HT is removed from the discharge R and connected to the
circuit.

When mains power is removed, the relay drops out straight away and the
discharge resistor is connected across the HT supply.

Cheers

Ian
>
>
> .... Phil
>
>
>
>

[Trevor Wilson]

"Ian Bell" > wrote in message
...
>I am trying to select a relay for a delayed HT switch (which will also
>discharge the HT when off). Most relays I can find have contacts rated at
>250VAC which translates into a peak of about 350V. However, data is scarce
>on what dc voltage these relays can switch. So far I have found only one
>that gives a dc current versus voltage curve and that stops at 210V dc (and
>200mA) and I really want to be able to switch up to 350V at up to 200mA.
>The rest just give a dc voltage at max current value.
>
> So, I am guessing that this problem has been faced before and there are
> relays that are known to work fine in this application. Any
> recommendations?
>
> By the way I prefer a 5V coil.

**Unless you have A LOT of cash, stick to switching AC. Most relays are
rated for a maximum of 27 VDC, regardless of the AC Voltage rating. Contrary
to your comments, ALL proper relay manufacturers clearly spell out the
maximum DC switching Voltage. Invariably, it will be less than 30 Volts.


--
Trevor Wilson
www.rageaudio.com.au

[Phil Allison[_3_]]

"Ian Bell"
> Phil Allison wrote:
>>
>> ** Post a schematic - you IDIOT.
>>
>> Still sounds like you are NOT breaking anything like 350 volts.
>>
>
> It is easy enough to describe. The relay common is connected to the HT
> supply (semiconductor rectifiers and RC smoothing). The NC contact is
> connected to ground via a resistor which is used to discharge the HT
> supply caps when power is turned off. The NO contact goes to the circuit
> to be powered by the supply. On power up the heater supply comes up right
> away but the relay is held off for say 30 secs. Then the relay is switched
> and HT is removed from the discharge R and connected to the circuit.
>
> When mains power is removed, the relay drops out straight away and the
> discharge resistor is connected across the HT supply.
>

** Everything depends on the "circuit" that is being powered - that is why
a schem is needed. The breaking capacity needed from the relay is NOT
simply the voltage and current being supplied to the load prior to opening.

The relay spec you quoted says the unit is OK to 210 volts DC ( across the
contacts) and 200mA - so the question is, with 140 volts (ie 350 - 210)
supplied to your "circuit" will it still draw 200mA ??

If not, the there will likely be no arcing problem as the conditions do not
exist for continuous arcing.

Also, if you add a suitable electro cap to the supply rail of the
"circuit" - that will prevent arcing entirely !!!

As little as 4.7uF should hold the voltage up on the "circuit" side long
enough ( say 1mS ) for the relay contacts to separate and be arc free.

IOW - go try a damn relay and stop playing dumb hypotheticals with
misunderstood specs.



..... Phil

[Ian Bell[_2_]]

Phil Allison wrote:
> "Ian Bell"
>> Phil Allison wrote:
>>> ** Post a schematic - you IDIOT.
>>>
>>> Still sounds like you are NOT breaking anything like 350 volts.
>>>
>> It is easy enough to describe. The relay common is connected to the HT
>> supply (semiconductor rectifiers and RC smoothing). The NC contact is
>> connected to ground via a resistor which is used to discharge the HT
>> supply caps when power is turned off. The NO contact goes to the circuit
>> to be powered by the supply. On power up the heater supply comes up right
>> away but the relay is held off for say 30 secs. Then the relay is switched
>> and HT is removed from the discharge R and connected to the circuit.
>>
>> When mains power is removed, the relay drops out straight away and the
>> discharge resistor is connected across the HT supply.
>>
>
> ** Everything depends on the "circuit" that is being powered - that is why
> a schem is needed. The breaking capacity needed from the relay is NOT
> simply the voltage and current being supplied to the load prior to opening.
>
> The relay spec you quoted says the unit is OK to 210 volts DC ( across the
> contacts) and 200mA - so the question is, with 140 volts (ie 350 - 210)
> supplied to your "circuit" will it still draw 200mA ??
>
> If not, the there will likely be no arcing problem as the conditions do not
> exist for continuous arcing.
>
> Also, if you add a suitable electro cap to the supply rail of the
> "circuit" - that will prevent arcing entirely !!!
>
> As little as 4.7uF should hold the voltage up on the "circuit" side long
> enough ( say 1mS ) for the relay contacts to separate and be arc free.
>
> IOW - go try a damn relay and stop playing dumb hypotheticals with
> misunderstood specs.
>
>
>
> .... Phil
>
>

Thanks for the input Phil. You have given me much to think about. I have
no experience of using relays to switch HT (but you already guessed
that) so the exact meaning of relay switching specs and the problems
they experience when used outside their obvious (but limited) specified
conditions is something I need to learn.

I was planning to try a relay or two as you suggest but I would like to
be in a position to apply this technique more generally so I need to
understand what is going one as well as merely having a working solution
for one specific applications. If you could point me to any written
material on the subject I would be grateful.

Cheers

Ian

[mick]

On Thu, 24 Dec 2009 14:09:07 +0000, Ian Bell wrote:

> I am trying to select a relay for a delayed HT switch (which will also
> discharge the HT when off). Most relays I can find have contacts rated
> at 250VAC which translates into a peak of about 350V. However, data is
> scarce on what dc voltage these relays can switch. So far I have found
> only one that gives a dc current versus voltage curve and that stops at
> 210V dc (and 200mA) and I really want to be able to switch up to 350V at
> up to 200mA. The rest just give a dc voltage at max current value.
>
> So, I am guessing that this problem has been faced before and there are
> relays that are known to work fine in this application. Any
> recommendations?
>
> By the way I prefer a 5V coil.
>


You've probably got all the info you need really, but the contact voltage
rating of a relay depends on the air gap. When switching AC any arc only
lasts until the voltage passes through zero, at which point the arc
extinguishes naturally. If the voltage is DC then the arc can maintain
indefinitely. You can increase the DC voltage switching capability by
connecting contacts in series, providing that they make and break
simultaneously. "Proper" DC switching devices often have powerful magnets
on each side of the contact gap. These pull the arc sideways on breaking,
allowing a closer contact gap than would be possible otherwise.

You also need to make very sure that the coil-contact voltage rating is
safe for your application. e.g. using an Omron MK2S ("octal" 2p) relay
with both n.o. contacts in series you get 250VDC per contact with up to
2500VAC contacts to coil isolation.

I would suggest that you connect the common of the c/o contact to earth
and switch the negative side of the supply. The n.c. contact can then
switch the bottom end of a resistor up to HT+. This way the relay coil
and frame can be at low voltage.


Relay info:
http://industrial.omron.co.uk/en/products/catalogue/switching_components/
electromechanical_relays/industrial_plug_in_relays/mk-s/default.html

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

[Phil Allison[_3_]]

"mick the prick "

>
> You also need to make very sure that the coil-contact voltage rating is
> safe for your application. e.g. using an Omron MK2S ("octal" 2p) relay
> with both n.o. contacts in series you get 250VDC per contact ..


** Omron do NOT state the switching capacity at 250V DC.

With the standard de-rating factors applied - it is likely only in the tens
of mAs.

Idiot.


...... Phil

[mick]

On Sat, 26 Dec 2009 10:11:46 +1100, Phil Allison wrote:

> "mick the prick "
>
>
>> You also need to make very sure that the coil-contact voltage rating is
>> safe for your application. e.g. using an Omron MK2S ("octal" 2p) relay
>> with both n.o. contacts in series you get 250VDC per contact ..
>
>
> ** Omron do NOT state the switching capacity at 250V DC.
>
> With the standard de-rating factors applied - it is likely only in the
> tens of mAs.
>
> Idiot.
>


No need to be offencive, Phil. Just because Omron don't provide a full
data sheet on the web.

They state a maximum switching voltage of 250VDC and a maximum switching
load of 300W on a n.o. contact (half of this for the n.c. contact). That
works out at 1.2A and 0.6A respectively (it won't be that high in real
life), if you can't be bothered with the maths. Admittedly though, they
also give a DC rating of 5A @ 30VDC but the DC loading doesn't follow a
linear curve against the voltage as you probably know.

If you would care to check out an alternative similar style relay (with
much better documentation), the Finder 60 series shows a graph, with DC
ratings up to 220v for 1, 2 & 3 contacts in series, and shows my point
about the non-linear curve very well. The 60.12 is a very similar unit to
the Omron and is used as a direct replacement in most cases.


Finder link:
http://www.findernet.com/en/products/profiles.php?serie=60&lang=en
Both the relay spec pdf and the General Technical Information pages are
worth a look.


--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

[Phil Allison[_3_]]

"mick the prick "
>
>> You also need to make very sure that the coil-contact voltage rating is
>>> safe for your application. e.g. using an Omron MK2S ("octal" 2p) relay
>>> with both n.o. contacts in series you get 250VDC per contact ..
>>
>>
>> ** Omron do NOT state the switching capacity at 250V DC.
>>
>> With the standard de-rating factors applied - it is likely only in the
>> tens of mAs.
>>
>> Idiot.
>>
>
>
> No need to be offencive,

** Stop posting crazy BULL**** !!

And I will not need to SHUT YOU UP.


> They state a maximum switching voltage of 250VDC and a maximum switching
> load of 300W on a n.o. contact (half of this for the n.c. contact).


** Again - you are just making up bull**** data.


> If you would care to check out an alternative similar style relay (with
> much better documentation), the Finder 60 series shows a graph, with DC
> ratings up to 220v for 1, 2 & 3 contacts in series,


** For one set of contacts - the max breaking rating is just over 100mA.

Funny how you did not want to POST that fact - eh ???

Drop Dead you DAMN LIAR !!!!



.... Phil

[mick]

On Sat, 26 Dec 2009 20:58:53 +1100, Phil Allison wrote:

<snip>
>
> ** Stop posting crazy BULL**** !!
>
> And I will not need to SHUT YOU UP.
>
>
>> They state a maximum switching voltage of 250VDC and a maximum
>> switching load of 300W on a n.o. contact (half of this for the n.c.
>> contact).
>
>
> ** Again - you are just making up bull**** data.
>

Yes pointless phil, I made it up from the data sheet... >>Yawn<<

>
>> If you would care to check out an alternative similar style relay (with
>> much better documentation), the Finder 60 series shows a graph, with DC
>> ratings up to 220v for 1, 2 & 3 contacts in series,
>
>
> ** For one set of contacts - the max breaking rating is just over 100mA.
>

Whee!!! It can read a graph!

> Funny how you did not want to POST that fact - eh ???
>
> Drop Dead you DAMN LIAR !!!!
>


Pillock...

That's why we series up multiple contacts then, isn't it?
Look at the damn graph again! For 2 contacts in series it's 400mA and for
3 contacts its about 900mA. Remember that you can allow up to 250v *per
contact* (although I don't personally like using the 3-pole relay like
this). You are ok switching 400mA resistive at 440VDC with a safety
margin if you series up both contacts on a 2-pole relay. Also, keep the
same polarity on the contacts to reduce stresses in the insulation.


--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

[Phil Allison[_3_]]

" mick the PRICK "

> Look at the damn graph again! For 2 contacts in series it's 400mA and for
> 3 contacts its about 900mA. Remember that you can allow up to 250v *per
> contact*


** Look at the damn graph again - you STINKING LIAR !!

The max voltage is only 220V for ALL three curves and conditions.

http://www.findernet.com/comuni/pdf/S60EN.pdf

See middle right of page 5.


**** OFF to HELL

- YOU PIG IGNORANT DAMN TROLL




...... Phil

[mick]

On Sat, 26 Dec 2009 23:57:38 +1100, Phil Allison wrote:

> " mick the PRICK "
>
>> Look at the damn graph again! For 2 contacts in series it's 400mA and
>> for 3 contacts its about 900mA. Remember that you can allow up to 250v
>> *per contact*
>
>
> ** Look at the damn graph again - you STINKING LIAR !!
>
> The max voltage is only 220V for ALL three curves and conditions.
>
> http://www.findernet.com/comuni/pdf/S60EN.pdf
>
> See middle right of page 5.
>
>
> **** OFF to HELL
>
> - YOU PIG IGNORANT DAMN TROLL
>
>



See page iv of the
General Technical document. Under DC1 in table 1 it states "The switching
voltage at the same current can be doubled by wiring 2 contacts in
series".

And a Very Merry Christmas to you too, Phil! :-)

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

[[email protected]]

On Sat, 26 Dec 2009 23:57:38 +1100, "Phil Allison" >
wrote:

>
>" mick the PRICK "
>
>> Look at the damn graph again! For 2 contacts in series it's 400mA and for
>> 3 contacts its about 900mA. Remember that you can allow up to 250v *per
>> contact*
>
>
>** Look at the damn graph again - you STINKING LIAR !!
>
> The max voltage is only 220V for ALL three curves and conditions.
>
> http://www.findernet.com/comuni/pdf/S60EN.pdf
>
> See middle right of page 5.
>
>
> **** OFF to HELL
>
> - YOU PIG IGNORANT DAMN TROLL
>
>
>
>
>..... Phil
>
>
>


Hello Phil,

I think that it would be more charitable to say that he was mistaken.

Why must you over react to any comment that you see is mistaken?

Kind regards

Bill Ramsay

[mick]

On Sun, 27 Dec 2009 08:14:33 +1300, beel wrote:

<snip>
>
> I think that it would be more charitable to say that he was mistaken.
>
> Why must you over react to any comment that you see is mistaken?
>


That's quite typical of Phil - something that I'm used to seeing a lot of
on here! It's just the way he is (and he'll probably insult me again for
saying that!). :-)

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

[Phil Allison[_3_]]

>

> Hello Phil,
>
> I think that it would be more charitable to say that he was mistaken.


** What a fool like you thinks does not matter.



..... Phil

[Edward Morris]

Phil needs attention. He didn't get enough of it as a child so he still
trying to get the attention he needs to grow up and be a man

He's got a long way to go.

Eddie

"Phil Allison" > wrote in message
...

>

> Hello Phil,
>
> I think that it would be more charitable to say that he was mistaken.


** What a fool like you thinks does not matter.



..... Phil

[[email protected]]

On Sun, 27 Dec 2009 10:15:03 +1100, "Phil Allison" >
wrote:

>
>
>
>> Hello Phil,
>>
>> I think that it would be more charitable to say that he was mistaken.
>
>
> ** What a fool like you thinks does not matter.
>
>
>
>.... Phil
>

Mighty fine words for someone who does not know me. So it's being
foolish to suggest that you lack charity, is it?

My Grandmother used to tell me that politeness costs nothing.

Shouting and being generally obnoxious seems to be your stock in
trade. It only illuminates either the paucity of your vocabulary,
mental state or general unwellness. Which is it?

Kind regards

Bill.

[Phil Allison[_3_]]

>> ** What a fool like you thinks does not matter.
>>
>
> Mighty fine words for someone who does not know me.


** You are very well known to me " Bill Ramsay"

- as a complete ASSHOLE !!



...... Phil

[[email protected]]

On Sun, 27 Dec 2009 15:54:54 +1100, "Phil Allison" >
wrote:

>

>
>>> ** What a fool like you thinks does not matter.
>>>
>>
>> Mighty fine words for someone who does not know me.
>
>
>** You are very well known to me " Bill Ramsay"
>
>- as a complete ASSHOLE !!
>
>
>
>..... Phil
>
oh sweetie, our secret is out!!!!

what is it that makes you so prescient?

Anyway, who gives a toss what a feeble minded vertically integrated
onanist like you 'thinks'.

love and hugs,


tell you what, shall we meet in the usual place?, you stand under the
railway clock with your little face going purple in rage, and of
course, the badger stuck up your bum.

Bill



>

[Phil Allison[_3_]]

>> ** What a fool like you thinks does not matter.
>
>
> Mighty fine words for someone who does not know me.


** You are very well known to me " Bill Ramsay"

- as a complete ASSHOLE !!


FOAD - you moronic PIG.


...... Phil

[Ian Bell[_2_]]

wrote:
> On Sun, 27 Dec 2009 15:54:54 +1100, "Phil Allison" >
> wrote:
>
>>
>>
>>>> ** What a fool like you thinks does not matter.
>>>>
>>> Mighty fine words for someone who does not know me.
>>
>> ** You are very well known to me " Bill Ramsay"
>>
>> - as a complete ASSHOLE !!
>>
>>
>>
>> ..... Phil
>>
> oh sweetie, our secret is out!!!!
>
> what is it that makes you so prescient?
>
> Anyway, who gives a toss what a feeble minded vertically integrated
> onanist like you 'thinks'.
>
> love and hugs,
>
>
> tell you what, shall we meet in the usual place?, you stand under the
> railway clock with your little face going purple in rage, and of
> course, the badger stuck up your bum.
>
> Bill
>
>
>


LOl!! I just love the bit about the badger up his bum LOL made my day.

Thanks Mate

Ian

[[email protected]]

On Sun, 27 Dec 2009 20:32:52 +1100, "Phil Allison" >
wrote:


>
>>> ** What a fool like you thinks does not matter.
>>
>>
>> Mighty fine words for someone who does not know me.
>
>
>** You are very well known to me " Bill Ramsay"
>
> - as a complete ASSHOLE !!
>
>
> FOAD - you moronic PIG.
>
>
>..... Phil
>
>
>

tell me phil do you still wear your full faced motor cycle helmet when
you meet people? I've heard you have to do that otherwise you'd have
a face like a well slapped arse!

[[email protected]]

On Sun, 27 Dec 2009 12:08:12 +0000, Ian Bell >
wrote:

wrote:
>> On Sun, 27 Dec 2009 15:54:54 +1100, "Phil Allison" >
>> wrote:
>>
>>>
>>>
>>>>> ** What a fool like you thinks does not matter.
>>>>>
>>>> Mighty fine words for someone who does not know me.
>>>
>>> ** You are very well known to me " Bill Ramsay"
>>>
>>> - as a complete ASSHOLE !!
>>>
>>>
>>>
>>> ..... Phil
>>>
>> oh sweetie, our secret is out!!!!
>>
>> what is it that makes you so prescient?
>>
>> Anyway, who gives a toss what a feeble minded vertically integrated
>> onanist like you 'thinks'.
>>
>> love and hugs,
>>
>>
>> tell you what, shall we meet in the usual place?, you stand under the
>> railway clock with your little face going purple in rage, and of
>> course, the badger stuck up your bum.
>>
>> Bill
>>
>>
>>
>
>
>LOl!! I just love the bit about the badger up his bum LOL made my day.
>
>Thanks Mate
>
>Ian

nil problemos, I do my best.

Kind regards

Bill.

[Ian Iveson]

Phil Allison wrote:

>> It is easy enough to describe. The relay common is
>> connected to the HT supply (semiconductor rectifiers and
>> RC smoothing). The NC contact is connected to ground via
>> a resistor which is used to discharge the HT supply caps
>> when power is turned off. The NO contact goes to the
>> circuit to be powered by the supply. On power up the
>> heater supply comes up right away but the relay is held
>> off for say 30 secs. Then the relay is switched and HT is
>> removed from the discharge R and connected to the
>> circuit.
>>
>> When mains power is removed, the relay drops out straight
>> away and the discharge resistor is connected across the
>> HT supply.
>>
>
> ** Everything depends on the "circuit" that is being
> powered - that is why a schem is needed. The breaking
> capacity needed from the relay is NOT simply the voltage
> and current being supplied to the load prior to opening.

Quite. And the exact shape of current and voltage over time,
for opening and closing conditions, can be modified by
changes to the circuit, which multiplies the complexity of
the selection problem. In these situations, I guess a
professional would copy whatever is commonly done.

> The relay spec you quoted says the unit is OK to 210 volts
> DC ( across the contacts) and 200mA - so the question
> is, with 140 volts (ie 350 - 210) supplied to your
> "circuit" will it still draw 200mA ??
>
> If not, the there will likely be no arcing problem as the
> conditions do not exist for continuous arcing.
>
> Also, if you add a suitable electro cap to the supply rail
> of the "circuit" - that will prevent arcing entirely !!!
>
> As little as 4.7uF should hold the voltage up on the
> "circuit" side long enough ( say 1mS ) for the relay
> contacts to separate and be arc free.
>
> IOW - go try a damn relay and stop playing dumb
> hypotheticals with misunderstood specs.

I quite like dumb hypotheticals. They don't *have* to be
dumb...any hypotheticals will do. What else is worth
discussing?

Ian could do what I guess a professional would do and ask
his suppliers. Some may have application guides available on
their sites, as may some manufacturers.

There are so many different relays on the market that
specification is presumably very narrow. DIY testing isn't
very practical, because many relays will do the job, but
some may not do it for very long. Ian would need to build a
tester, and test a lot of relays, a lot of times each. The
prospect of failure raises the question, incidentally, of
its possible consequences. The circuit must be able to
tolerate a contact stuck in either the open or closed
position. An advantage of using two in series is that it's
very unlikely that both would stick closed.

A SCR or other semiconductor solution may be worth
considering. They aren't so various, so I guess
specification must be broader, or applications narrower.
Their data sheets are probably pretty extensive too.

Although I'm loath to point this out to a self-proclaimed
professional who hopes to profit from his electronics
business, contact specifications for the two different
applications he cites are quite different, as are the
consequences of failure, so using a single relay is unlikely
to be an optimum solution. Using a relay to drain HT
capacitors is unnecessary, and a simple relay or SCR on the
primary side of a separate HT transformer would be a
sensible and common enough solution to make selection easy.

Ian

[Phil Allison[_3_]]

"Ian Iveson"

** Ian Bell has posted just two objectives:

1. To switch off the HT as soon as the AC power is removed from the PSU.

2. The switch of the HT if the PSU connector is removed from the load
device.


Requirement 1 is a nonsense.

Requirement 2 can be done with any relay cos it is " dry " switching.

Bell is a total MORON !!!



..... Phil

[[email protected]]

On Mon, 28 Dec 2009 14:50:24 +1100, "Phil Allison" >
wrote:

>
>"Ian Iveson"
>
>** Ian Bell has posted just two objectives:
>
>1. To switch off the HT as soon as the AC power is removed from the PSU.
>
>2. The switch of the HT if the PSU connector is removed from the load
>device.
>
>
>Requirement 1 is a nonsense.
>
>Requirement 2 can be done with any relay cos it is " dry " switching.
>
>Bell is a total MORON !!!
>
>
>
>.... Phil
>

an alternative way to say this of course, could be.

1. I don't think that's really necessary as ....................

2. This is a very good idea, any relay will do for this purpose as
it is dry switching.

Kind regards


etc.

why don't you try that for a change? you'll be surprised by the more
pleasant reaction you'll get. You'll also be able to take off that
full face helmet when you go out in public.