I'm looking for a solid state relay that has an input of 240V a/c and that can switch DC on the output side ie switch 12v DC to ground.
I have been using the old style relays (Omron MY2NJ) in the past but these dont seem to last to long. So far I can only find solid state ones that have A/c on the out put side.

On 30/12/2020 19:31, Bazza wrote:
I'm looking for a solid state relay that has an input of 240V a/c and
that can switch DC on the output side ie switch 12v DC to ground. I
have been using the old style relays (Omron MY2NJ) in the past but
these dont seem to last to long. So far I can only find solid state
ones that have A/c on the out put side.

I think you need to specify what current you want to switch and whether
or not it is an inductive load before any sensible advice it possible.

One company I knew who changed to using solid state relays inadvisedly
managed to have their kit catch fire with monotonous regularity.

You should be asking why are the classical relays are failing first.

--
Regards,
Martin Brown

On Wednesday, 30 December 2020 at 19:47:03 UTC, Martin Brown wrote:

I think you need to specify what current you want to switch and whether
or not it is an inductive load before any sensible advice it possible.

One company I knew who changed to using solid state relays inadvisedly
managed to have their kit catch fire with monotonous regularity.

You should be asking why are the classical relays are failing first.

Allow me to clarify.
The current I want to switch is negligible because CCTV camera works on only 12V DC. I want to switch the cameras continuous 12v D/C output signal to ground by having the relay switch from NO to NC.
The relay on the other side will be activated by a 240volt a/c input. So a 240v input will switch a 12v D/c to ground

Bazza wrote:
On Wednesday, 30 December 2020 at 19:47:03 UTC, Martin Brown wrote:

I think you need to specify what current you want to switch and whether
or not it is an inductive load before any sensible advice it possible.

One company I knew who changed to using solid state relays inadvisedly
managed to have their kit catch fire with monotonous regularity.

You should be asking why are the classical relays are failing first.

Allow me to clarify.
The current I want to switch is negligible because CCTV camera works on
only 12V DC.

Er, that's a non-sequitur, or even worse. If it's "only 12v" then the
current you need to switch is going to be a *lot* more than the
current you would need to switch if the device was powered by a 240v
supply, to be exact about 20 times as much current!

Not to mention that switching DC is harder on contacts than switching
AC.


I want to switch the cameras continuous 12v D/C output signal
to ground by having the relay switch from NO to NC.
The relay on the other side will be activated by a 240volt a/c input. So
a 240v input will switch a 12v D/c to ground

That makes no sense at all. Are you switching the *signal* from the
camera or the 12 volt power to the camera?

I *think* I understand that you want the relay to be operated by a
240v supply, not unusual/impossible but 240v relays are not the norm.

--
Chris Green
·

Chris Green laid this down on his screen :
Not to mention that switching DC is harder on contacts than switching
AC.

A suitable diode across the contacts will help.

On 30/12/2020 20:44, Chris Green wrote:
Bazza wrote:
On Wednesday, 30 December 2020 at 19:47:03 UTC, Martin Brown wrote:

I think you need to specify what current you want to switch and whether
or not it is an inductive load before any sensible advice it possible.

One company I knew who changed to using solid state relays inadvisedly
managed to have their kit catch fire with monotonous regularity.

You should be asking why are the classical relays are failing first.

Allow me to clarify.
The current I want to switch is negligible because CCTV camera works on
only 12V DC.

Er, that's a non-sequitur, or even worse. If it's "only 12v" then the
current you need to switch is going to be a *lot* more than the
current you would need to switch if the device was powered by a 240v
supply, to be exact about 20 times as much current!

Not to mention that switching DC is harder on contacts than switching
AC.


I want to switch the cameras continuous 12v D/C output signal
to ground by having the relay switch from NO to NC.
The relay on the other side will be activated by a 240volt a/c input. So
a 240v input will switch a 12v D/c to ground

That makes no sense at all. Are you switching the *signal* from the
camera or the 12 volt power to the camera?

I *think* I understand that you want the relay to be operated by a
240v supply, not unusual/impossible but 240v relays are not the norm.

The "matchbox" sized solid state relays are readily available for mains
or LV operation.

https://www.ebay.co.uk/itm/SSR-25AA-...AOSwTpZeFO2 Q

On Wed, 30 Dec 2020 12:28:15 -0800 (PST), Bazza wrote:

You should be asking why are the classical relays are failing
first.

Allow me to clarify.
The current I want to switch is negligible because CCTV camera works on
only 12V DC.

Say 5 W for the camera, half an amp. Any IR LEDs in the camera
sharing this supply? They could easyly double or treble that 5 W
load. So 1 A or more is quite possible and not "negligable".

I want to switch the cameras continuous 12v D/C output signal to ground

What do you mean by "12v D/C output signal"? Is it an auxillary 12 V
power source for other kit or, as "signal" implies, a 12 V output
that is set by events in the camera (motion detect or WHY).

Shorting a power supply is not normally a good idea and has a
tendancy to release the magic smoke out of the power source?
Shorting a PSU through relay the contacts could be why the relays are
failing...

If it is a signal *output* why do you want to connect it to ground? A
signal *input* I could understand to tell the camera about some
external event.

... by having the relay switch from NO to NC.

"switch from Normally Open to Normally Closed." Mutally exclusive. I
think you mean you want a Normally Open contact pair that closes when
the relay coil is energised.

The relay on the other side will be activated by a 240volt a/c input. So
a 240v input will switch a 12v D/c to ground

Still worried about this 12 V being connected to ground...

--
Cheers
Dave.

On Wed, 30 Dec 2020 21:58:34 GMT, Harry Bloomfield, Esq.
wrote:

Chris Green laid this down on his screen :
Not to mention that switching DC is harder on contacts than switching
AC.

A suitable diode across the contacts will help.

ITYM to reduce back EMF one would use a diode reverse-biased across
the coil of the relay. To stop sparking across contacts a suitable
capacitor would be a better bet.

In article ,
Bazza wrote:
I'm looking for a solid state relay that has an input of 240V a/c and
that can switch DC on the output side ie switch 12v DC to ground. I have
been using the old style relays (Omron MY2NJ) in the past but these dont
seem to last to long. So far I can only find solid state ones that have
A/c on the out put side.

How often does it operate? I've got 240v relays working here that are 40
years old.

--
*Of course I'm against sin; I'm against anything that I'm too old to enjoy.

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

Cursitor Doom wrote:
On Wed, 30 Dec 2020 21:58:34 GMT, Harry Bloomfield, Esq.
wrote:

Chris Green laid this down on his screen :
Not to mention that switching DC is harder on contacts than switching
AC.
A suitable diode across the contacts will help.

ITYM to reduce back EMF one would use a diode reverse-biased across
the coil of the relay. To stop sparking across contacts a suitable
capacitor would be a better bet.


These are referred to as "snubber circuits" and
can be tuned for good results. The people in
sci.electronics know how to do that. There was
at least one guy over there, who wrote a textbook
of electronic design. A kind of "resident perfessor".

http://electronicsbeliever.com/snubb...sign-analysis/

An RLC makes sense, since the R is the dissipative part. That's
where the electrons go to die.

And you "tune" the snubber to the thing to be snubbed. It's
not a random thing. Someone who knows what they're doing
can reduce the ringback to almost nothing. If the characteristics
of the load are not known with any precision, you can breadboard
the circuit and change values until it's tame. Snubbing a relay
coil should be a slam-dunk, as the relay composition will not
vary too much from unit to unit.

Paul

On 30/12/2020 20:28, Bazza wrote:
On Wednesday, 30 December 2020 at 19:47:03 UTC, Martin Brown wrote:

I think you need to specify what current you want to switch and whether
or not it is an inductive load before any sensible advice it possible.

One company I knew who changed to using solid state relays inadvisedly
managed to have their kit catch fire with monotonous regularity.

You should be asking why are the classical relays are failing first.

Allow me to clarify.
The current I want to switch is negligible because CCTV camera works on only 12V DC. I want to switch the cameras continuous 12v D/C output signal to ground by having the relay switch from NO to NC.
The relay on the other side will be activated by a 240volt a/c input. So a 240v input will switch a 12v D/c to ground

Really you can pretty much BUILD that out of a mosfet, and some high
voltage diodes....


--
New Socialism consists essentially in being seen to have your heart in
the right place whilst your head is in the clouds and your hand is in
someone else's pocket.

On 30/12/2020 20:28, Bazza wrote:
On Wednesday, 30 December 2020 at 19:47:03 UTC, Martin Brown wrote:

I think you need to specify what current you want to switch and
whether or not it is an inductive load before any sensible advice
it possible.

One company I knew who changed to using solid state relays
inadvisedly managed to have their kit catch fire with monotonous
regularity.

You should be asking why are the classical relays are failing
first.

Allow me to clarify. The current I want to switch is negligible
because CCTV camera works on only 12V DC. I want to switch the
cameras continuous 12v D/C output signal to ground by having the
relay switch from NO to NC. The relay on the other side will be
activated by a 240volt a/c input. So a 240v input will switch a 12v
D/c to ground

You haven't made any sense at all.
Why do you want to short 12v to ground?

That is sure to degrade both the relay and the camera.

--
Regards,
Martin Brown

On Wed, 30 Dec 2020 11:31:14 -0800 (PST), Bazza
wrote:

I'm looking for a solid state relay that has an input of 240V a/c and that can switch DC on the output side ie switch 12v DC to ground.
I have been using the old style relays (Omron MY2NJ) in the past but these dont seem to last to long. So far I can only find solid state ones that have A/c on the out put side.
Some of the answers the OP has already given suggest that he really
doesn't know enough to start messing around with diodes or other
circuit components (no criticism of him intended).

newshound used his keyboard to write :
The "matchbox" sized solid state relays are readily available for mains or LV
operation.

https://www.ebay.co.uk/itm/SSR-25AA-...AOSwTpZeFO2 Q

It's to switch DC.

In article ,
Harry Bloomfield wrote:
newshound used his keyboard to write :
The "matchbox" sized solid state relays are readily available for mains or LV
operation.

https://www.ebay.co.uk/itm/SSR-25AA-...AOSwTpZeFO2 Q

It's to switch DC.

It would take a true optimist to guarantee a solid state relay will have a
longer life than a traditional one.

--
*In "Casablanca", Humphrey Bogart never said "Play it again, Sam" *

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

On 31/12/2020 10:11, Davidm wrote:
On Wed, 30 Dec 2020 11:31:14 -0800 (PST), Bazza
wrote:

I'm looking for a solid state relay that has an input of 240V a/c and that can switch DC on the output side ie switch 12v DC to ground.
I have been using the old style relays (Omron MY2NJ) in the past but these dont seem to last to long. So far I can only find solid state ones that have A/c on the out put side.
Some of the answers the OP has already given suggest that he really
doesn't know enough to start messing around with diodes or other
circuit components (no criticism of him intended).



If mechanical relays are failing it suggests that shorting a 12V output
to ground is not a sensible thing to do. I'm not sure what the OP is
attempting to achieve by shorting out a 12V supply rather than just
switching it off.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 31/12/2020 12:55, alan_m wrote:
On 31/12/2020 10:11, Davidm wrote:
On Wed, 30 Dec 2020 11:31:14 -0800 (PST), Bazza
wrote:

I'm looking for a solid state relay that has an input of 240V a/c and
that can switch DC on the output side ie switch 12v DC to ground.
I have been using the old style relays (Omron MY2NJ) in the past but
these dont seem to last to long. So far I can only find solid state
ones that have A/c on the out put side.
Some of the answers the OP has already given suggest that he really
doesn't know enough to start messing around with diodes or other
circuit components (no criticism of him intended).



If mechanical relays are failing it suggests that shorting a 12V output
to ground is not a sensible thing to do.Â* I'm not sure what the OP is
attempting to achieve by shorting out a 12V supply rather than just
switching it off.

I think he doesn't mean switching an zero impedance 12v supply to
ground, but switching a 12 v supply via a load, to ground

anyway this sort of thing works

https://uk.rs-online.com/web/p/solid...elays/8886843/

Its rated at 30V DC maximum control voltage and 0.5A switch current
But if course you need to generate the input DC somehow.

Or even for very low currents this works...

https://www.ebay.co.uk/itm/240V-220V...-/272619019157




--
You can get much farther with a kind word and a gun than you can with a
kind word alone.

Al Capone

Apologies for not explaining the electrical details in a professional manner and maybe I should have found a forum for CCTV matters. I'm not an electrician but an elderly and pretty capable DIYer.

As I said earlier I have been using old style (coil) relays specifically the MY2NJ type and they have worked with the 5 cameras I have.
I use a 240v PIR sensor that sends 240v to the relay when it is activated. The relay, when activated, makes or breaks contact in the camera. This triggers the camera to start recording. Here is an extract from the manual...........
"""Trigger
This is the cause or stimulus which defines when to trigger the Network Camera. The trigger source can be external digital input devices. This option allows the Network Camera to use an external digital input device or sensor as a trigger source. Depending on your application, there are many choices with digital input devices on the market which help detect changes in temperature, vibration, sound, light,"""

Bazza wrote:

I use a 240v PIR sensor that sends 240v to the relay when it is activated. The relay, when activated, makes or breaks contact in the camera.

is this volt-free contact on the camera, or a 12V input to the camera?

if the latter, you could feed the 240V to a 12V DC PSU, and use that to
trigger the camera

All the mains coil relays that RS supply, can switch DC as well as AC

https://uk.rs-online.com/web/c/relays/general-purpose-relays/non-latching-relays/?sra=p&applied-dimensions=4291338473

In article ,
Bazza wrote:

Apologies for not explaining the electrical details in a professional
manner and maybe I should have found a forum for CCTV matters. I'm not
an electrician but an elderly and pretty capable DIYer.

As I said earlier I have been using old style (coil) relays specifically
the MY2NJ type and they have worked with the 5 cameras I have. I use a
240v PIR sensor that sends 240v to the relay when it is activated. The
relay, when activated, makes or breaks contact in the camera. This
triggers the camera to start recording. Here is an extract from the
manual.......... """Trigger This is the cause or stimulus which defines
when to trigger the Network Camera. The trigger source can be external
digital input devices. This option allows the Network Camera to use an
external digital input device or sensor as a trigger source. Depending
on your application, there are many choices with digital input devices
on the market which help detect changes in temperature, vibration,
sound, light,"""

If that relay is a specified one, it sounds like they've got it wrong.

Go to CPC etc and buy one of the spec you need - perhaps a higher current
rating.

And if the contacts are giving trouble, add a diode across them (or buy
one with it built in) An inductive load at DC can shorten the life of
marginal contacts.

--
*Prepositions are not words to end sentences with *

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

On 31/12/2020 10:16, Harry Bloomfield wrote:
newshound used his keyboard to write :
The "matchbox" sized solid state relays are readily available for
mains or LV operation.

https://www.ebay.co.uk/itm/SSR-25AA-...AOSwTpZeFO2 Q


It's to switch DC.

No, it will switch AC or DC from an AC signal.

On 31/12/2020 11:08, Dave Plowman (News) wrote:
In article ,
Harry Bloomfield wrote:
newshound used his keyboard to write :
The "matchbox" sized solid state relays are readily available for mains or LV
operation.

https://www.ebay.co.uk/itm/SSR-25AA-...AOSwTpZeFO2 Q

It's to switch DC.

It would take a true optimist to guarantee a solid state relay will have a
longer life than a traditional one.

I shifted an application from octal base conventional relays to these
because of relay failures, and these have been far more reliable
(although not completely infallible).

On 31/12/2020 00:41, Dave Plowman (News) wrote:
In article ,
Bazza wrote:
I'm looking for a solid state relay that has an input of 240V a/c and
that can switch DC on the output side ie switch 12v DC to ground. I have
been using the old style relays (Omron MY2NJ) in the past but these dont
seem to last to long. So far I can only find solid state ones that have
A/c on the out put side.

How often does it operate? I've got 240v relays working here that are 40
years old.

Come to think of it so have I. They switch quite frequently.

Bill

On 31/12/2020 13:31, Bazza wrote:

Apologies for not explaining the electrical details in a professional
manner and maybe I should have found a forum for CCTV matters. I'm
not an electrician but an elderly and pretty capable DIYer.

As I said earlier I have been using old style (coil) relays
specifically the MY2NJ type and they have worked with the 5 cameras I
have. I use a 240v PIR sensor that sends 240v to the relay when it is
activated. The relay, when activated, makes or breaks contact in the
camera. This triggers the camera to start recording. Here is an
extract from the manual.......... """Trigger This is the cause or
stimulus which defines when to trigger the Network Camera. The
trigger source can be external digital input devices. This option
allows the Network Camera to use an external digital input device or
sensor as a trigger source. Depending on your application, there are
many choices with digital input devices on the market which help
detect changes in temperature, vibration, sound, light,"""


Well it still is not clear as to what the relay connects to what.
But if its is just a matter of sensing mains and shoving a digital
voltage to a pin then that opto isolator I linked too is perfect



--
"It is an established fact to 97% confidence limits that left wing
conspirators see right wing conspiracies everywhere"

On 31/12/2020 13:31, Bazza wrote:

Apologies for not explaining the electrical details in a professional
manner and maybe I should have found a forum for CCTV matters. I'm
not an electrician but an elderly and pretty capable DIYer.

As I said earlier I have been using old style (coil) relays
specifically the MY2NJ type and they have worked with the 5 cameras I
have. I use a 240v PIR sensor that sends 240v to the relay when it is
activated. The relay, when activated, makes or breaks contact in the
camera. This triggers the camera to start recording. Here is an
extract from the manual.......... """Trigger This is the cause or
stimulus which defines when to trigger the Network Camera. The
trigger source can be external digital input devices. This option
allows the Network Camera to use an external digital input device or
sensor as a trigger source. Depending on your application, there are
many choices with digital input devices on the market which help
detect changes in temperature, vibration, sound, light,"""

You might be better off and safer using a 12v PIR device then.

I presume that the trigger action is to pull the trigger input to the
camera low in order to activate it. *How* are the relays failing?

Reviews online suggest some dodgy imitations/fakes about - where the
coil burns out if they are on for significant periods of time..

--
Regards,
Martin Brown

Yes snubber networks can stop a lot of that sort of thing and they won't
make a big pulse of interference then either.
Brian

--

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"Martin Brown" wrote in message
...
On 30/12/2020 19:31, Bazza wrote:
I'm looking for a solid state relay that has an input of 240V a/c and
that can switch DC on the output side ie switch 12v DC to ground. I
have been using the old style relays (Omron MY2NJ) in the past but
these dont seem to last to long. So far I can only find solid state
ones that have A/c on the out put side.

I think you need to specify what current you want to switch and whether or
not it is an inductive load before any sensible advice it possible.

One company I knew who changed to using solid state relays inadvisedly
managed to have their kit catch fire with monotonous regularity.

You should be asking why are the classical relays are failing first.

--
Regards,
Martin Brown

Still not clear, would not simply open circuiting the 12v supply do the job
why are you earthing it or do you really mean, disconnect and earth the
supply pin on the camera?
Brian

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"Bazza" wrote in message
...
On Wednesday, 30 December 2020 at 19:47:03 UTC, Martin Brown wrote:

I think you need to specify what current you want to switch and whether
or not it is an inductive load before any sensible advice it possible.

One company I knew who changed to using solid state relays inadvisedly
managed to have their kit catch fire with monotonous regularity.

You should be asking why are the classical relays are failing first.

Allow me to clarify.
The current I want to switch is negligible because CCTV camera works on
only 12V DC. I want to switch the cameras continuous 12v D/C output
signal to ground by having the relay switch from NO to NC.
The relay on the other side will be activated by a 240volt a/c input. So a
240v input will switch a 12v D/c to ground

If you want sa 240 v relay, then simply strip down a wall wart 5v usb
device for its pcb, and use a 5v relay solid stat or whatever on its output.
Brian

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"Chris Green" wrote in message
...
Bazza wrote:
On Wednesday, 30 December 2020 at 19:47:03 UTC, Martin Brown wrote:

I think you need to specify what current you want to switch and whether
or not it is an inductive load before any sensible advice it possible.

One company I knew who changed to using solid state relays inadvisedly
managed to have their kit catch fire with monotonous regularity.

You should be asking why are the classical relays are failing first.

Allow me to clarify.
The current I want to switch is negligible because CCTV camera works on
only 12V DC.

Er, that's a non-sequitur, or even worse. If it's "only 12v" then the
current you need to switch is going to be a *lot* more than the
current you would need to switch if the device was powered by a 240v
supply, to be exact about 20 times as much current!

Not to mention that switching DC is harder on contacts than switching
AC.


I want to switch the cameras continuous 12v D/C output
signal
to ground by having the relay switch from NO to NC.
The relay on the other side will be activated by a 240volt a/c input. So
a 240v input will switch a 12v D/c to ground

That makes no sense at all. Are you switching the *signal* from the
camera or the 12 volt power to the camera?

I *think* I understand that you want the relay to be operated by a
240v supply, not unusual/impossible but 240v relays are not the norm.

--
Chris Green
·

Yes and possibly aa high value resistor and a capacitor as well.
Brian

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Harry Bloomfield; "Esq." wrote in message
...
Chris Green laid this down on his screen :
Not to mention that switching DC is harder on contacts than switching
AC.

A suitable diode across the contacts will help.

In article ,
newshound wrote:
On 31/12/2020 11:08, Dave Plowman (News) wrote:
In article ,
Harry Bloomfield wrote:
newshound used his keyboard to write :
The "matchbox" sized solid state relays are readily available for mains or LV
operation.

https://www.ebay.co.uk/itm/SSR-25AA-...AOSwTpZeFO2 Q

It's to switch DC.

It would take a true optimist to guarantee a solid state relay will have a
longer life than a traditional one.

I shifted an application from octal base conventional relays to these
because of relay failures, and these have been far more reliable
(although not completely infallible).

Well remember the first SS relays I was aware of. Used to switch the 'on
air' lights in a newly refurbished TV studio. Hardly a day existed where
they all worked. ;-)

--
*The sooner you fall behind, the more time you'll have to catch up *

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

The main issue with low current devices and relays is tarnishing I used to
find. Some of the ones in cases were not really sealed very well and the
contacts easily corroded due to the atmosphere. Speaker relays seem to
suffer dirty contacts as well though and these switch at zero current but
do need to take high currents in use which is when I find the channels go up
and down till you clean their contacts.
Sorry for the digression. I'm still not sure what the original query was
attempting to do and why exactly.
Brian

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"Cursitor Doom" wrote in message
...
On Wed, 30 Dec 2020 21:58:34 GMT, Harry Bloomfield, Esq.
wrote:

Chris Green laid this down on his screen :
Not to mention that switching DC is harder on contacts than switching
AC.

A suitable diode across the contacts will help.

ITYM to reduce back EMF one would use a diode reverse-biased across
the coil of the relay. To stop sparking across contacts a suitable
capacitor would be a better bet.

On Thu, 31 Dec 2020 11:08:22 +0000 (GMT), Dave Plowman (News) wrote:

It would take a true optimist to guarantee a solid state relay will have
a longer life than a traditional one.

Depnds on the application. I doubt a traditional relay would last
long operating with a 7 Hz PWM signal to control the speed of a mains
circulating pump. Might be a tad noisy (acoustically and
electrically) as well. B-)

--
Cheers
Dave.

On 31/12/2020 16:35, Dave Liquorice wrote:
On Thu, 31 Dec 2020 11:08:22 +0000 (GMT), Dave Plowman (News) wrote:

It would take a true optimist to guarantee a solid state relay will have
a longer life than a traditional one.

Depnds on the application. I doubt a traditional relay would last
long operating with a 7 Hz PWM signal to control the speed of a mains
circulating pump. Might be a tad noisy (acoustically and
electrically) as well. B-)

Pore Ole Dave. No, any person knowledgeable in electronics could tell
you that .

Mechanical stuff wears out and arcs and sparks make it so., Solid state
stuff suffers dopant migration, but under reasonable temperature
conditions the lifetime will be 10-1000 times greater.




--
"When one man dies it's a tragedy. When thousands die it's statistics."

Josef Stalin

On Thu, 31 Dec 2020 05:31:10 -0800 (PST), Bazza wrote:

Apologies for not explaining the electrical details in a professional
manner and maybe I should have found a forum for CCTV matters. I'm not
an electrician but an elderly and pretty capable DIYer.

No worries, I think everyone is confused about what you are trying to
achieve.

As I said earlier I have been using old style (coil) relays specifically the MY2NJ type and they have worked with the 5 cameras I have.

What is the failure mode of these relay(s)? Omron are a reputable
make with good specs and normally good life times.

I use a 240v PIR sensor that sends 240v to the relay when it is
activated. The relay, when activated, makes or breaks contact in the
camera. This triggers the camera to start recording.

OK follow that. Can't think what is going on to kill relays under the
conditions expected by that description. The PIR isn't likely to
switch often enough to wear out a relay in a time that makes
replacing it an annoyance. Say 10 operations/night, 500,000
operations lifetime of relay = 137 years. Even at 100 ops/night
that's 13 years! and the 500,000 could be on the low side, 5,000,000
might be nearer. B-)

Here is an extract from the manual...........
"""Trigger
This is the cause or stimulus which defines when to trigger the Network
Camera. The trigger source can be external digital input devices. This
option allows the Network Camera to use an external digital input device
or sensor as a trigger source. Depending on your application, there are
many choices with digital input devices on the market which help detect
changes in temperature, vibration, sound, light,"""

Unfortunately that doesn't help a great deal. We need to know more
about what the camera is expecting to find at its trigger input. What
make/model camera are they?

--
Cheers
Dave.

On 31/12/2020 16:09, Dave Plowman (News) wrote:
In article ,
newshound wrote:
On 31/12/2020 11:08, Dave Plowman (News) wrote:
In article ,
Harry Bloomfield wrote:
newshound used his keyboard to write :
The "matchbox" sized solid state relays are readily available for mains or LV
operation.

https://www.ebay.co.uk/itm/SSR-25AA-...AOSwTpZeFO2 Q

It's to switch DC.

It would take a true optimist to guarantee a solid state relay will have a
longer life than a traditional one.

I shifted an application from octal base conventional relays to these
because of relay failures, and these have been far more reliable
(although not completely infallible).

Lifetimes for relay based logic running a few daily tasks should be of
the order of 30 or 40 years if properly designed. That is about how long
my oil burner controller lasted before relays started to fail.
Well remember the first SS relays I was aware of. Used to switch the 'on
air' lights in a newly refurbished TV studio. Hardly a day existed where
they all worked. ;-)

If they were not being driven exactly right then you were very lucky
none of them caught fire. Though our loads were a lot more than a lamp.
Modern ones are more tolerant but still not bomb proof.

--
Regards,
Martin Brown

On 31/12/2020 13:31, Bazza wrote:

Apologies for not explaining the electrical details in a professional manner and maybe I should have found a forum for CCTV matters. I'm not an electrician but an elderly and pretty capable DIYer.

As I said earlier I have been using old style (coil) relays specifically the MY2NJ type and they have worked with the 5 cameras I have.
I use a 240v PIR sensor that sends 240v to the relay when it is activated. The relay, when activated, makes or breaks contact in the camera. This triggers the camera to start recording. Here is an extract from the manual..........
"""Trigger
This is the cause or stimulus which defines when to trigger the Network Camera. The trigger source can be external digital input devices. This option allows the Network Camera to use an external digital input device or sensor as a trigger source. Depending on your application, there are many choices with digital input devices on the market which help detect changes in temperature, vibration, sound, light,"""


Next time try giving a clue like the make or model number. It helps!

Googling "This is the cause or stimulus which defines when to trigger
the Network Camera", this camera looks to be a vivotek_pz8121 or similar.

The camera input has a pull up to 12v, and shorting that to ground
triggers it to record.

The 10A relay contacts are probably now some tarnished metal as the
current is too low to keep them 'wet'[*], and probably a better choice
will be one specified to switch signals rather than power.

Something like a reed relay with gold/silver plated contacts.

The coils of these tend to low voltage, so you will need a transformer
like an an old mobile phone charger or maybe an LED driver transformer
which usefully have terminals you can wire to, and maybe also use to
switch on additional LED lighting?

You can use other components to get rid of the transformer, and use an
optocoupler instead of the relay, but that might be taking a risk with
electronics construction abilities and mains voltages.

* - https://en.wikipedia.org/wiki/Wetting_current

--
Adrian C

On 31/12/2020 18:32, Adrian Caspersz wrote:


You can use other components to get rid of the transformer, and use an
optocoupler instead of the relay, but that might be taking a risk with
electronics construction abilities and mains voltages.

* - https://en.wikipedia.org/wiki/Wetting_current


Ok, this is a cheap ready assembled pcb without a relay.

https://www.ebay.co.uk/itm/240V-220V...-/272619019157

Should be OK to switch 12V, the EL817 chip used is rated to 35V at 50mA.

The UK eBay seller neatly covers himself with "Please be very careful
with mains electricity - it can kill!"

--
Adrian C

On 31/12/2020 18:32, Adrian Caspersz wrote:
Next time try giving a clue like the make or model number. It helps!

Googling "This is the cause or stimulus which defines when to trigger
the Network Camera", this camera looks to be a vivotek_pz8121 or similar.

The camera input has a pull up to 12v, and shorting that to ground
triggers it to record.

The little opto isolator board I linked to should do exactly that

https://www.ebay.co.uk/itm/240V-220V...-/272619019157

Just connect ground to ground and the output to the camera trigger.
Leave the other output pin disconnected It should work!

Obviously a housing would be needed for outdoor work


--
"The most difficult subjects can be explained to the most slow witted
man if he has not formed any idea of them already; but the simplest
thing cannot be made clear to the most intelligent man if he is firmly
persuaded that he knows already, without a shadow of doubt, what is laid
before him."

- Leo Tolstoy

On 31/12/2020 19:02, Adrian Caspersz wrote:
On 31/12/2020 18:32, Adrian Caspersz wrote:


You can use other components to get rid of the transformer, and use an
optocoupler instead of the relay, but that might be taking a risk with
electronics construction abilities and mains voltages.

* - https://en.wikipedia.org/wiki/Wetting_current


Ok, this is a cheap ready assembled pcb without a relay.

https://www.ebay.co.uk/itm/240V-220V...-/272619019157


Great minds...
Should be OK to switch 12V, the EL817 chip used is rated to 35V at 50mA.

Ah,. I hadnt got that far!

The UK eBay seller neatly covers himself with "Please be very careful
with mains electricity - it can kill!"

Of course



--
€œIdeas are inherently conservative. They yield not to the attack of
other ideas but to the massive onslaught of circumstance"

- John K Galbraith

On Wednesday, 30 December 2020 at 20:28:18 UTC, Bazza wrote:
On Wednesday, 30 December 2020 at 19:47:03 UTC, Martin Brown wrote:

I think you need to specify what current you want to switch and whether
or not it is an inductive load before any sensible advice it possible.

One company I knew who changed to using solid state relays inadvisedly
managed to have their kit catch fire with monotonous regularity.

You should be asking why are the classical relays are failing first.

Allow me to clarify.
The current I want to switch is negligible because CCTV camera works on only 12V DC. I want to switch the cameras continuous 12v D/C output signal to ground by having the relay switch from NO to NC.
The relay on the other side will be activated by a 240volt a/c input. So a 240v input will switch a 12v D/c to ground
I'm struggling to understand what you are trying to achieve. I'm running cctv systems around the farm and another in our village hall which record continuously day and night onto hard disc drives in standard dvr's. The 16 channel hd kits record over 7 days before overwriting while the 8 channel lower definition units have longer retention times. All the cameras and the recorders are powered by 12 volt dc supplies. The camera signals to the dvr's are 1 volt peak to peak into 75 ohms. The dvr has its own smps rated at 3A, the cameras are split over multiple smps units for redundancy but most of the cameras are well below 1A each