Just discovered that the power to the shed had tripped.

The master RCD in the shed had tripped.
The RCD on the single circuit had not tripped.
The RCBO in the house had tripped.

The freezer had not fully defrosted - just the top layer (chest freezer) but
it was fortunate we bought something to freeze today and so noted that it
wasn't running.

So we need to put some prcautions in place.

Presumably there are several things we can do:
(1) Attach some kind of power fail alarm to the RCBO end of the circuit in
the house
(2) Attach some kind of wireless (or wired if we manage to pull the CAT5E
through) alarm to the freezer circuit in the shed so we are warned if this
fails.

Just starting Googling, but checking here to see if anyone has already
worked out a solution.

Cheers

Dave R
--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

On Jan 8, 12:57*pm, "David WE Roberts" wrote:
Just discovered that the power to the shed had tripped.

The master RCD in the shed had tripped.
The RCD on the single circuit had not tripped.
The RCBO in the house had tripped.

The freezer had not fully defrosted - just the top layer (chest freezer) but
it was fortunate we bought something to freeze today and so noted that it
wasn't running.

So we need to put some prcautions in place.

Presumably there are several things we can do:
(1) Attach some kind of power fail alarm to the RCBO end of the circuit in
the house
(2) Attach some kind of wireless (or wired if we manage to pull the CAT5E
through) alarm to the freezer circuit in the shed so we are warned if this
fails.

Just starting Googling, but checking here to see if anyone has already
worked out a solution.

is a shed window visible from house? would a neon (as on a FCU) be
visible?

Jim K

David WE Roberts wrote:
Presumably there are several things we can do:
(1) Attach some kind of power fail alarm to the RCBO end of the circuit
in the house
(2) Attach some kind of wireless (or wired if we manage to pull the
CAT5E through) alarm to the freezer circuit in the shed so we are warned
if this fails.

Just starting Googling, but checking here to see if anyone has already
worked out a solution.

Something like this?:-

http://www.oncallmedicalsupplies.com...ermometer.html

(Just the first link I found for "wireless freezer alarm") I don't know
what range you need, though.

If you can run an extra cable. then a simple normally closed relay
contact at the far end, powered by the mains, connected to an alarm in
the house would do it. It only needs to be a low voltage, low current
link, so nothing special in the way of armouring or protection is
needed. If you use a radio link, then it needs to transmit regular
pulses while there is power at the far end so that it fails safe. IMO,
just fitting an alarm to the house end of the wiring, though easy, would
give you a false sense of security.

--
Tciao for Now!

John.

On Tue, 8 Jan 2013 05:18:05 -0800 (PST), Jim K wrote:

is a shed window visible from house? would a neon (as on a FCU) be
visible?

That was my first thought, KISS. There is no need for instant
notification of failure just indication that will be noticed at some
point. Even a mains panel mounted neon under the eaves on a side facing
the kitchen window would do.

--
Cheers
Dave.

Dave Liquorice wrote:
That was my first thought, KISS. There is no need for instant
notification of failure just indication that will be noticed at some
point. Even a mains panel mounted neon under the eaves on a side facing
the kitchen window would do.

But humans are bad at noticing something that isn't there. So a light that
goes out when the power is off will be noticed much more slowly than a light
that comes on, especially if it's flashing.

How about a flashing bike light, suitably modified so it turns on in
flashing mode when power is removed? Possibly wired up to something bigger
than the AAAs they're usually powered by.

Theo

In message , Huge
writes
On 2013-01-08, Dave Liquorice wrote:
On Tue, 8 Jan 2013 05:18:05 -0800 (PST), Jim K wrote:

is a shed window visible from house? would a neon (as on a FCU) be
visible?

That was my first thought, KISS. There is no need for instant
notification of failure just indication that will be noticed at some
point. Even a mains panel mounted neon under the eaves on a side facing
the kitchen window would do.

That's what I've done with my cesspit pump. A mains neon mounted above
the cess-pit where it's visible from the house.

The other thing I need is a "drain blocked" warning - I'm still working
on a sensor for this.

Mercury switch in a float? Only if you have a convenient inspection pit.

--
Tim Lamb

On Jan 9, 9:46 am, Huge wrote:
On 2013-01-08, Dave Liquorice wrote:

On Tue, 8 Jan 2013 05:18:05 -0800 (PST), Jim K wrote:

is a shed window visible from house? would a neon (as on a FCU) be
visible?

That was my first thought, KISS. There is no need for instant
notification of failure just indication that will be noticed at some
point. Even a mains panel mounted neon under the eaves on a side facing
the kitchen window would do.

That's what I've done with my cesspit pump. A mains neon mounted above
the cess-pit where it's visible from the house.

The other thing I need is a "drain blocked" warning - I'm still working
on a sensor for this.

bilge pump float switch?

Jim K

On Jan 9, 10:31 am, Huge wrote:
On 2013-01-09, Tim Lamb wrote:



In message , Huge
writes
On 2013-01-08, Dave Liquorice wrote:
On Tue, 8 Jan 2013 05:18:05 -0800 (PST), Jim K wrote:

is a shed window visible from house? would a neon (as on a FCU) be
visible?

That was my first thought, KISS. There is no need for instant
notification of failure just indication that will be noticed at some
point. Even a mains panel mounted neon under the eaves on a side facing
the kitchen window would do.

That's what I've done with my cesspit pump. A mains neon mounted above
the cess-pit where it's visible from the house.

The other thing I need is a "drain blocked" warning - I'm still working
on a sensor for this.

Mercury switch in a float? Only if you have a convenient inspection pit.

Oh, I have a submersible switch already, it's just mounting it, running
cabling, where to put the warning light and finding the round tuit that
are the issues.

so "I'm still working on a sensor for this. "

was a bit misleading then?

Jim K

"David WE Roberts" writes:

(2) Attach some kind of wireless (or wired if we manage to
pull the CAT5E through) alarm to the freezer circuit in the
shed so we are warned if this fails.

Wind a large electromagnet, wire it to the mains in the shed and
have it hold up an iron weight on the end of a rope attached to
a flag pole. When the power cuts off a flag is raised. Im not
sure what the correct flag for €œfood about to go off€� is.

--
Jón Fairbairn
http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2012-10-07)

On 9 Jan, 10:57, Jon Fairbairn wrote:
"David WE Roberts" writes:

(2) Attach some kind of wireless (or wired if we manage to
pull the CAT5E through) alarm to the freezer circuit in the
shed so we are warned if this fails.

Wind a large electromagnet, wire it to the mains in the shed and
have it hold up an iron weight on the end of a rope attached to
a flag pole. When the power cuts off a flag is raised. I’m not
sure what the correct flag for “food about to go off” is.

as a deluxe model could you get it to launch a 1/2 brick through the
kitchen window with a note wrapped around it warning of the impending
doom?

Jim K

On 9 Jan, 11:07, Huge wrote:
On 2013-01-09, Jim K wrote:









On Jan 9, 10:31 am, Huge wrote:
On 2013-01-09, Tim Lamb wrote:

In message , Huge
writes
On 2013-01-08, Dave Liquorice wrote:
On Tue, 8 Jan 2013 05:18:05 -0800 (PST), Jim K wrote:

is a shed window visible from house? would a neon (as on a FCU) be
visible?

That was my first thought, KISS. There is no need for instant
notification of failure just indication that will be noticed at some
point. Even a mains panel mounted neon under the eaves on a side facing
the kitchen window would do.

That's what I've done with my cesspit pump. A mains neon mounted above
the cess-pit where it's visible from the house.

The other thing I need is a "drain blocked" warning - I'm still working
on a sensor for this.

Mercury switch in a float? Only if you have a convenient inspection pit.

Oh, I have a submersible switch already, it's just mounting it, running
cabling, where to put the warning light and finding the round tuit that
are the issues.

so "I'm still working on a sensor for this. "

was a bit misleading then?

Nope. I need some way to mount the submersible switch. I was going to use
an end stop in plastic waste and run the cabling up the inside of the pipe,
but I haven't found a suitable end stop yet, and I'm not sure how I'm going
to mount the pipe inside the inspection chamber.

sounds like a drawback of a submersible...

Jim K

On Tuesday, January 8, 2013 12:57:02 PM UTC, David WE Roberts wrote:
(1) Attach some kind of power fail alarm to the RCBO end of the circuit in
the house

Old non-maintained (?) safety light on the outside of the shed. Only comes on when the power fails.

On Wed, 9 Jan 2013 09:33:20 -0800 (PST), Andy Dingley wrote:

Old non-maintained (?) ...

Correct, non-maintained are off until the power fails. Maintained are on
all the time, power or no power. Both until their batteries are flat.

... safety light on the outside of the shed. Only comes on when the
power fails.

But from stock with a good batteries you only have 3hrs to notice, if you
are away at work for 8+ hours/day...

Simpler to have a mains relay, battery and flashing LED. Get a relay that
will fit a DIN rail mounted socket and it can be in the shed CU. Modern
high brightness LEDs take naff all current so a D cell or similar will
last for years.

--
Cheers
Dave.

On Tuesday, January 8, 2013 12:57:02 PM UTC, David WE Roberts wrote:
Just discovered that the power to the shed had tripped.

230V relay in shed, NC contacts are open when power is on, closed if power goes off. 12V battery (shed alarm?) connected through the NC contacts to any suitable device, alarm sounder or light. That doesn't help if the freezer fails or if someone unplugs it, you may want a thermostat as well.

On Wednesday, 9 January 2013 20:28:09 UTC, Dave Liquorice wrote:
On Wed, 9 Jan 2013 09:33:20 -0800 (PST), Andy Dingley wrote:



Old non-maintained (?) ...



Correct, non-maintained are off until the power fails. Maintained are on

all the time, power or no power. Both until their batteries are flat.



... safety light on the outside of the shed. Only comes on when the

power fails.



But from stock with a good batteries you only have 3hrs to notice, if you

are away at work for 8+ hours/day...



Simpler to have a mains relay, battery and flashing LED. Get a relay that

will fit a DIN rail mounted socket and it can be in the shed CU. Modern

high brightness LEDs take naff all current so a D cell or similar will

last for years.

Warning of mains failure is all well and good, but doesn't cover the freezer itself failing. While you're about it, why not fit a baby monitor (wireless or mains-signalling) relaying the freezer's own temperature-sensing beeper or an add-on one. It would also alert you of burglars.

Chris

On 9 Jan, 22:17, Onetap wrote:
On Tuesday, January 8, 2013 12:57:02 PM UTC, David WE Roberts wrote:
Just discovered that the power to the shed had tripped.

230V relay in shed, NC contacts are open when power is on, closed if power goes off. 12V battery (shed alarm?) connected through the NC contacts to any suitable device, alarm sounder or light. That doesn't help if the freezer fails or if someone unplugs it, you may want a thermostat as well.

if its a sounder and you are out at work for 8+hours I expect someone
with a clipboard (or a hammer) will be along to sort things out for
you....

Jim K

On Wed, 9 Jan 2013 16:44:51 -0800 (PST),
wrote:

Warning of mains failure is all well and good, but doesn't cover the
freezer itself failing.

Wouldn't that be covered by contents insurance, where as power failure
not caused by a general power cut wouldn't be?

While you're about it, why not fit a baby monitor (wireless or
mains-signalling) relaying the freezer's own temperature-sensing beeper

If it has one, one of ours doesn't just a very dim red light ...

... or an add-on one.

OK. B-)

It would also alert you of burglars.

A drive you potty when it's windy. I have a baby monitor in the loft to
listen to the mouse traps, gets very noisy when the wind gets up...

--
Cheers
Dave.

On 9 Jan 2013 11:07:01 GMT, Huge wrote:

The other thing I need is a "drain blocked" warning - I'm still
working on a sensor for this.

Mercury switch in a float? Only if you have a convenient inspection
pit.

Oh, I have a submersible switch already, it's just mounting it,
running cabling, where to put the warning light and finding the round
tuit that are the issues.

so "I'm still working on a sensor for this. " was a bit misleading
then?

Nope.

Well you have the sensor as in something that tells you water level, just
not installed it, different thing... I have the sensors to monitor the
pumps heating etc here even the box but want 6" of DIN rail to mount them
on.

I need some way to mount the submersible switch. I was going to use
an end stop in plastic waste and run the cabling up the inside of the
pipe, but I haven't found a suitable end stop yet, and I'm not sure how
I'm going to mount the pipe inside the inspection chamber.

All seems a bit complex. Float, stick, flag. Water level rises float
lifts stick with flag on top.

--
Cheers
Dave.

"Jon Fairbairn" wrote in message
...
"David WE Roberts" writes:

(2) Attach some kind of wireless (or wired if we manage to
pull the CAT5E through) alarm to the freezer circuit in the
shed so we are warned if this fails.

Wind a large electromagnet, wire it to the mains in the shed and
have it hold up an iron weight on the end of a rope attached to
a flag pole. When the power cuts off a flag is raised. Im not
sure what the correct flag for €œfood about to go off€� is.


Strangely, this (and other mixed electro-mechanical devices) had already
occurred to me but been discarded as fun but too whimsical :-)

--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

On Thu, 10 Jan 2013 09:51:26 -0000, David WE Roberts wrote:

Wind a large electromagnet, wire it to the mains in the shed and
have it hold up an iron weight on the end of a rope attached to
a flag pole. When the power cuts off a flag is raised. I m not
sure what the correct flag for food about to go off is.

Strangely, this (and other mixed electro-mechanical devices) had
already occurred to me but been discarded as fun but too whimsical :-)

Nothing wrong with whimsical. You wouldn't need a large electromagnet to
physically hold the weight up, just hold a latch that stops the weight
falling. The weight can be on the end of pivoted arm like a trafficator
(if you remember those devices).

--
Cheers
Dave.

On 10/01/2013 10:15, Dave Liquorice wrote:
Nothing wrong with whimsical. You wouldn't need a large electromagnet to
physically hold the weight up, just hold a latch that stops the weight
falling. The weight can be on the end of pivoted arm like a trafficator
(if you remember those devices).

You don't even need an electromagnet. All you need is a weight frozen to
the inside of the lid of the freezer to pull the flag up

Andy

On 10 Jan, 10:22, Huge wrote:
On 2013-01-10, Dave Liquorice wrote:

On 9 Jan 2013 11:07:01 GMT, Huge wrote:
I need some way to mount the submersible switch. I was going to use
an end stop in plastic waste and run the cabling up the inside of the
pipe, but I haven't found a suitable end stop yet, and I'm not sure how
I'm going to mount the pipe inside the inspection chamber.

All seems a bit complex. Float, stick, flag. Water level rises float
lifts stick with flag on top.

;) but which flag??

Making that gas (and hence stink) tight would be an issue. The relevant
inspection chamber is right outside the front door.

sure if you really wanted any help you'd post some decent details?

good luck with it anyway ;)

Jim K

On Thu, 10 Jan 2013 20:52:08 +0000, Andy Champ wrote:

Nothing wrong with whimsical. You wouldn't need a large electromagnet
to physically hold the weight up, just hold a latch that stops the
weight falling. The weight can be on the end of pivoted arm like a
trafficator (if you remember those devices).

You don't even need an electromagnet. All you need is a weight frozen
to the inside of the lid of the freezer to pull the flag up

Thought the idea of this mains fialure indicator was to get power
restored before the freezer had defrosted. B-)

--
Cheers
Dave.

On Fri, 11 Jan 2013 10:42:30 -0000, David WE Roberts wrote:

You don't even need an electromagnet. All you need is a weight frozen
to the inside of the lid of the freezer to pull the flag up

Thought the idea of this mains fialure indicator was to get power
restored before the freezer had defrosted. B-)

The top of the freezer will be warmest and defrost first.

Maybe.

The weight might also be frozen to the lid with something with a lower
freezing point than water so it thaws before the food..

I can't think of anything that freezes between 0C and -15C ... so that
might be a slight snag. Salt solution of correct proportion?

All this does of course mean cutting through the insulation in the
freezer top with enough clearance to allow the flag to move freely, but
with no air access to the inside or condensation will freeze the flag
to the top (although hopefully the thaw will clear this as well as
releasing the weight..

No need for a hole, the object inside is a rare earth magnet the end of
the flag string is attached to a bit of iron and held by the magnet until
the salt solution thaws and the magnet drops away. Need a non magnetic
freezer lid of course and careful adjustment on test of the attraction
between the bit of iron and the weight of the magnet.

--
Cheers
Dave.

On 11 Jan, 16:18, "Dave Liquorice"
wrote:
On Fri, 11 Jan 2013 10:42:30 -0000, David WE Roberts wrote:
You don't even need an electromagnet. All you need is a weight frozen
to the inside of the lid of the freezer to pull the flag up

Thought the idea of this mains fialure indicator was to get power
restored before the freezer had defrosted. B-)

The top of the freezer will be warmest and defrost first.

Maybe.

The weight might also be frozen to the lid with something with a lower
freezing point than water so it thaws before the food..

I can't think of anything that freezes between 0C and -15C ... so that
might be a slight snag. Salt solution of correct proportion?

All this does of course mean cutting through the insulation in the
freezer top with enough clearance to allow the flag to move freely, but
with no air access to the inside or condensation will freeze the flag
to the top (although hopefully the thaw will clear this as well as
releasing the weight..

No need for a hole, the object inside is a rare earth magnet the end of
the flag string is attached to a bit of iron and held by the magnet until
the salt solution thaws and the magnet drops away.

how will a bit of iron now lying on top of a freezer lid raise a flag
up a pole?

Need a non magnetic
freezer lid of course and careful adjustment on test of the attraction
between the bit of iron and the weight of the magnet.

if the flag raising mechanism is to be sprung (see point above) that
could be a helluva ££ RE magnet....

Jim K

On Fri, 11 Jan 2013 08:34:17 -0800 (PST), Jim K wrote:

No need for a hole, the object inside is a rare earth magnet the end
of the flag string is attached to a bit of iron and held by the magnet
until the salt solution thaws and the magnet drops away.

how will a bit of iron now lying on top of a freezer lid raise a flag
up a pole?

The string runs up to a pulley and across to another and then to the base
of the flag pole, running up the flag pole to a pulley at the top back
down to the flag. Weight is attached to first span to lift the iron off
the freezer lid when the magnet drops. Makes the AOT easier as one can
balance the attractive force with the weight.

Whimsical is fun. B-)

--
Cheers
Dave.

On 11 Jan, 17:42, "Dave Liquorice"
wrote:
On Fri, 11 Jan 2013 08:34:17 -0800 (PST), Jim K wrote:
No need for a hole, the object inside is a rare earth magnet the end
of the flag string is attached to a bit of iron and held by the magnet
until the salt solution thaws and the magnet drops away.

how will a bit of iron now lying on top of a freezer lid raise a flag
up a pole?

The string runs up to a pulley and across to another and then to the base
of the flag pole, running up the flag pole to a pulley at the top back
down to the flag. Weight is attached to first span to lift the iron off
the freezer lid when the magnet drops. Makes the AOT easier as one can
balance the attractive force with the weight.

Whimsical is fun. *B-)

indeed, Wilf Lunn is go ;)

altho in your scheme the RE magnet will be holding up that weight too -
so will still be £££ and large?

Jim K

On Fri, 11 Jan 2013 11:04:17 -0800 (PST), Jim K wrote:

No need for a hole, the object inside is a rare earth magnet the end
of the flag string is attached to a bit of iron and held by the
magnet until the salt solution thaws and the magnet drops away.

how will a bit of iron now lying on top of a freezer lid raise a flag
up a pole?

The string runs up to a pulley and across to another and then to the
base of the flag pole, running up the flag pole to a pulley at the top
back down to the flag. Weight is attached to first span to lift the
iron off the freezer lid when the magnet drops. Makes the AOT easier
as one can balance the attractive force with the weight.

Whimsical is fun. *B-)

indeed, Wilf Lunn is go ;)

Wilf's stuff was good but if *anything* of his involved something going
bang the sensible members of the crew left the studio...

altho in your scheme the RE magnet will be holding up that weight too -
so will still be £££ and large?

No the weight of the iron will be just over balanced by the suspended
weight. So the RE magnet only needs to provide minimal attractive force
to the iron.

--
Cheers
Dave.

On 11 Jan, 21:01, "Dave Liquorice"
wrote:
On Fri, 11 Jan 2013 11:04:17 -0800 (PST), Jim K wrote:
No need for a hole, the object inside is a rare earth magnet the end
of the flag string is attached to a bit of iron and held by the
magnet until the salt solution thaws and the magnet drops away.

how will a bit of iron now lying on top of a freezer lid raise a flag
up a pole?

The string runs up to a pulley and across to another and then to the
base of the flag pole, running up the flag pole to a pulley at the top
back down to the flag. Weight is attached to first span to lift the
iron off the freezer lid when the magnet drops. Makes the AOT easier
as one can balance the attractive force with the weight.

Whimsical is fun. *B-)

indeed, Wilf Lunn is go ;)

Wilf's stuff was good but if *anything* of his involved something going
bang the sensible members of the crew left the studio...

Great Egg Race then?

altho in your scheme the RE magnet will be holding up that weight too -
so will still be £££ and large?

No the weight of the iron will be just over balanced by the suspended
weight. So the RE magnet only needs to provide minimal attractive force
to the iron.

mmm but will that bit of iron have enough mass to pull the flag up
presumably 6ft? whilst its only say 2'6" off floor next to freezer
(allowing for a bit o sag in the string?)

Jim K

On 11/01/2013 21:19, Jim K wrote:
mmm but will that bit of iron have enough mass to pull the flag up
presumably 6ft? whilst its only say 2'6" off floor next to freezer
(allowing for a bit o sag in the string?)

Doesn't need to. It only needs to operate a trigger. Another weight can
then pull the flag up

Andy

On 08/01/2013 12:57, David WE Roberts wrote:
Just discovered that the power to the shed had tripped.

The master RCD in the shed had tripped. The RCD on the single circuit
had not tripped. The RCBO in the house had tripped.


Why do you need 3 RCDs? Wouldn't just one in the house be sufficient?
And perhaps the circuit attached to a light in the house to signify
power to the shed was OK.

On 11 Jan, 22:44, Andy Champ wrote:
On 11/01/2013 21:19, Jim K wrote:

mmm but will that bit of iron have enough mass to pull the flag up
presumably 6ft? whilst its only say 2'6" off floor next to freezer
(allowing for a bit o sag in the string?)

Doesn't need to. It only needs to operate a trigger. Another weight can
then pull the flag up

Andy

aha I love it when a plan comes together

Jim K

On Fri, 11 Jan 2013 13:19:00 -0800 (PST), Jim K wrote:

Wilf's stuff was good but if *anything* of his involved something
going bang the sensible members of the crew left the studio...

Great Egg Race then?

Vision On and various programmes hosted by Tony Hart after Vision On
finished.

altho in your scheme the RE magnet will be holding up that weight too
- so will still be £££ and large?

No the weight of the iron will be just over balanced by the suspended
weight. So the RE magnet only needs to provide minimal attractive
force to the iron.

mmm but will that bit of iron have enough mass to pull the flag up
presumably 6ft? whilst its only say 2'6" off floor next to freezer
(allowing for a bit o sag in the string?)

Well the iron and weight could be quite heavy with the iron just a tad
lighter. When the RE magnet falls and releases the iron, the weight will
pull it up to the pulley where it will get stopped. The weight continues
to fall raising the flag with all of it's weight acting on the string.
The weight can start near the ceiling.

--
Cheers
Dave.

"Fredxx" wrote in message
...
On 08/01/2013 12:57, David WE Roberts wrote:
Just discovered that the power to the shed had tripped.

The master RCD in the shed had tripped. The RCD on the single circuit
had not tripped. The RCBO in the house had tripped.


Why do you need 3 RCDs? Wouldn't just one in the house be sufficient?
And perhaps the circuit attached to a light in the house to signify
power to the shed was OK.

Shed has the CU which used to be in the house - so 13 amp and lighting
circuits (and possibly others) can be run round the shed.
Shed is 'Mother Of All Sheds' posted about a couple of years back, so quite
large.

So there is an 13 amp circuit with a breaker, whole CU breaker, then an RCBO
in the new fuse board in the house.

--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

On 12 Jan, 00:41, "Dave Liquorice"
wrote:
On Fri, 11 Jan 2013 13:19:00 -0800 (PST), Jim K wrote:
Wilf's stuff was good but if *anything* of his involved something
going bang the sensible members of the crew left the studio...

Great Egg Race then?

Vision On and various programmes hosted by Tony Hart after Vision On
finished.

altho in your scheme the RE magnet will be holding up that weight too
- so will still be £££ and large?

No the weight of the iron will be just over balanced by the suspended
weight. So the RE magnet only needs to provide minimal attractive
force to the iron.

mmm but will that bit of iron have enough mass to pull the flag up
presumably 6ft? whilst its only say 2'6" off floor next to freezer
(allowing for a bit o sag in the string?)

Well the iron and weight could be quite heavy with the iron just a tad
lighter. When the RE magnet falls and releases the iron, the weight will
pull it up to the pulley where it will get stopped. The weight continues
to fall raising the flag with all of it's weight acting on the string.
The weight can start near the ceiling.

yebbut still the only thing keeping your weight up aloft is the RE
magnet holding some lump of iron? ergo large RE magnet and £££, also
take longer to warm up and drop once freezer fails... all for a load
of 2008 lidl fishfingers?

Jim K

On Sat, 12 Jan 2013 07:51:38 -0800 (PST), Jim K wrote:

No the weight of the iron will be just over balanced by the
suspended weight. So the RE magnet only needs to provide minimal
attractive force to the iron.

mmm but will that bit of iron have enough mass to pull the flag up
presumably 6ft? whilst its only say 2'6" off floor next to freezer
(allowing for a bit o sag in the string?)

Well the iron and weight could be quite heavy with the iron just a tad
lighter. When the RE magnet falls and releases the iron, the weight
will pull it up to the pulley where it will get stopped. The weight
continues to fall raising the flag with all of it's weight acting on
the string. The weight can start near the ceiling.

yebbut still the only thing keeping your weight up aloft is the RE
magnet holding some lump of iron? ergo large RE magnet and £££,

No. Say the weight weighs 1kg and the lump of iron 999g all the RE magnet
has to provide is 1g of attractive force for the system to be balanced
and thus static. When the magnet falls away under it's own weight (it
will have to weigh more than 1g) the iron/weight/pulley system is
unbalanced and the weight can lift the iron to the pulley.

--
Cheers
Dave.