I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

.. wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

You're over thinking the problem:

http://www.ebay.co.uk/itm/Vintage-Me... em417b171d2e

As long as the outage isn't exactly 12 hours, natch.

--
Scott

Where are we going and why am I in this handbasket?

On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)


A mains operated analogue clock or, as those are quite rare these days,
one of these:

http://www.timeguard.com/products/ti...ime-controller

Simply compare time shown when you get home with the correct time.

Colin Bignell

"." wrote in message
...
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

Our microwave oven clock showing a row of zeros does the job nicely.

On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)


Coupled with the microwave, the oven, and other clocks in the house
being zeroed, my intruder alarm logs whenever the power goes off, and
when it comes back again, if i want to see how long it was off for.

--
Toby...
Remove your pants to reply

On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)


After a power outage the oven says "STOP". And the central heating
timer will be the amount behind the power was off for. I sometimes use
this to see how long a job on the electrics took and say to SWMBO "look,
replacing x only took y minutes!". And get a condescending "that's nice
dear" in return.

On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

My LED clock/ alarm hasn't got the backup battery fitted, so when I get
home, if it's flashing, I know when the power last came back on. If you
have a mechanical timeswitch anywhere, it will be running slow by the
total length of the power cuts since it was last corrected. A mechanical
timeswitch set to "always on" feeding power to the clock is a Heath
Robinson approach to having both items of information in the same area.

--
Tciao for Now!

John.

On Monday 06 January 2014 18:05 wrote in uk.d-i-y:

I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

If you can find a nice old proper mains clock with a synchronous motor, that
will tell you how long the power has been out...

--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

On Monday 06 January 2014 18:08 Scott M wrote in uk.d-i-y:

. wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

You're over thinking the problem:

http://www.ebay.co.uk/itm/Vintage-Me... em417b171d2e

As long as the outage isn't exactly 12 hours, natch.


Beat me to it!

--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

On 06/01/2014 19:15, Tim Watts wrote:
On Monday 06 January 2014 18:05 wrote in uk.d-i-y:

I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

If you can find a nice old proper mains clock with a synchronous motor, that
will tell you how long the power has been out...

Available in most large supermarkets. They're sold as 24 hour mechanical
timers, although the face *can* be a little hard to read, being so small.

--
Tciao for Now!

John.

On Monday, January 6, 2014 6:05:04 PM UTC, MM wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

Relay, LED, RC, reset pushswitch


NT

On 06/01/14 19:04, Piers wrote:
On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)


After a power outage the oven says "STOP". And the central heating
timer will be the amount behind the power was off for. I sometimes use
this to see how long a job on the electrics took and say to SWMBO "look,
replacing x only took y minutes!". And get a condescending "that's nice
dear" in return.

small raspberry pi that makes a log entry every minute, and has ntp.

look for the boot log to find when it booted and the last entry in the
log from the timer....


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

Any cooker with a mains powered digital clock or for that matter most
cheap mains powered digital clocks that lack a standby battery. The
result is modulo 1 day but usually more than good enough.

The modern digital teasmade is particularly annoying in this respect.

--
Regards,
Martin Brown

Tim Watts wrote:
On Monday 06 January 2014 18:08 Scott M wrote in uk.d-i-y:

. wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)
You're over thinking the problem:

http://www.ebay.co.uk/itm/Vintage-Me... em417b171d2e

As long as the outage isn't exactly 12 hours, natch.


Beat me to it!

:-)

--
Scott

Where are we going and why am I in this handbasket?

On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

Any decent UPS with management facilities allows you to view the history
of the supply.

--
Rod

"." wrote in message
...
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out,

I've got a mains alarm clock that does all this for you :-)

On Mon, 06 Jan 2014 18:05:04 +0000, . wrote:

I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

For the unsophisticated version you could use a non latching* plug in
RCD adapter which will trip on loss of power.
Some have a little indicator window which changes colour when they
have been tripped while on others a button will be further out.

* Can you get latching ones in plug in form?

G.Harman

On Mon, 06 Jan 2014 22:01:18 +0000
polygonum wrote:

On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really
cool to have a gizmo to plug into the mains, then light an LED if
the power goes out, e.g. in a storm. A more sophisticated version
would also say how long the power was out, e.g. 1 LED = 1 hour, 2
LEDs 2 hours and so on. Obviously, it would need a battery to keep
the LEDs lighted if the power went off. Does something like this
exist already? (Yes, I've Googled!)

Any decent UPS with management facilities allows you to view the
history of the supply.


Just received an APC UPS this morning. Perfect timing!
--
Davey.

On Tue, 7 Jan 2014 00:10:59 +0000, Davey wrote:

Any decent UPS with management facilities allows you to view the
history of the supply.

Just received an APC UPS this morning. Perfect timing!

The smaller ones rely on the connected host PC to do the logging...

--
Cheers
Dave.

On Tue, 07 Jan 2014 00:14:53 +0000 (GMT)
"Dave Liquorice" wrote:

On Tue, 7 Jan 2014 00:10:59 +0000, Davey wrote:

Any decent UPS with management facilities allows you to view the
history of the supply.

Just received an APC UPS this morning. Perfect timing!

The smaller ones rely on the connected host PC to do the logging...


This particular 6-socket one is for the TV, PVR etc. I had a similar one
some years ago in the US, and it kept its own memory, and told the PC
what had happened when it was plugged in to it. I haven't set this one
up yet, so have no idea what it does for history.

--
Davey.

On Mon, 06 Jan 2014 19:43:07 +0000, The Natural Philosopher
wrote:

small raspberry pi that makes a log entry every minute, and has ntp.

look for the boot log to find when it booted and the last entry in the
log from the timer....

Best idea yet! Especially as I was given a RPi for Christmas and am
already experimenting with it!

On Mon, 06 Jan 2014 22:01:18 +0000, polygonum
wrote:

On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

Any decent UPS with management facilities allows you to view the history
of the supply.

Whew! Nice idea, but UPS's are not cheap! The mains-powered analogue
clock is a good idea, but I like the one about the Raspberry Pi the
best (so far!)

On Tue, 07 Jan 2014 00:14:53 +0000 (GMT), "Dave Liquorice"
wrote:

On Tue, 7 Jan 2014 00:10:59 +0000, Davey wrote:

Any decent UPS with management facilities allows you to view the
history of the supply.

Just received an APC UPS this morning. Perfect timing!

The smaller ones rely on the connected host PC to do the logging...

Oops, yes, that's what my UPS does, connected to the PC. And I always
switch off the PC when I go away. (I could leave a little old
Raspberry Pi switched on, though...) Come to that, I do also have a
Basic Stamp with mains adaptor...

On 07/01/2014 02:57, . wrote:
On Mon, 06 Jan 2014 22:01:18 +0000, polygonum
wrote:

On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

Any decent UPS with management facilities allows you to view the history
of the supply.

Whew! Nice idea, but UPS's are not cheap! The mains-powered analogue
clock is a good idea, but I like the one about the Raspberry Pi the
best (so far!)

Not part of the original spec. to be affordable! :-)

--
Rod

On 07/01/14 02:54, . wrote:
On Mon, 06 Jan 2014 19:43:07 +0000, The Natural Philosopher
wrote:

small raspberry pi that makes a log entry every minute, and has ntp.

look for the boot log to find when it booted and the last entry in the
log from the timer....

Best idea yet! Especially as I was given a RPi for Christmas and am
already experimenting with it!

If you power it from a trickle charged battery, it will even stay up
when power is down. What you can then do is - say - ping your router or
something that is always on and look for when it isn't.


Either a shell script or something that opens a connection to a socket
on the router..or does e.g. an SNMP call. Failure of that indicates
router powered off.

I have suitable C code used here to monitor my router every 5 minutes
using SNMP.

somest8mes tenet works as an alternative.

Or some routers can be persuaded to log to a remote IP address.

Or you ,might even cobble together a way of detecting mains (say an
optical isolator fed from the mains) on some sort of I/O pin.


Cron is your friend here.



--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

Dunno but does it matter how long? I have an old timer here which is mains
driven with no battery back up, thus when the mains goes of, even for a few
seconds if left in over ride the relay drops out. thus if the device you
left on is off when you return the power went off.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"." wrote in message
...
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

On Tue, 07 Jan 2014 08:53:35 +0000, The Natural Philosopher
wrote:

Or you ,might even cobble together a way of detecting mains (say an
optical isolator fed from the mains) on some sort of I/O pin.

My bro (electronics degree) said re another kind of sensor that I
could create to sense mains electricity flowing would be just by
winding some coils of wire around the mains cable, which would
generate a small voltage when the mains is on or nothing when it's
off. This could then be fed to the RPi or to a Basic Stamp, with
suitable amplification of the signal as necessary.

On Tue, 07 Jan 2014 07:13:01 +0000, polygonum
wrote:

On 07/01/2014 02:57, . wrote:
On Mon, 06 Jan 2014 22:01:18 +0000, polygonum
wrote:

On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)

Any decent UPS with management facilities allows you to view the history
of the supply.

Whew! Nice idea, but UPS's are not cheap! The mains-powered analogue
clock is a good idea, but I like the one about the Raspberry Pi the
best (so far!)

Not part of the original spec. to be affordable! :-)

True!

On 07/01/2014 09:24, . wrote:
On Tue, 07 Jan 2014 08:53:35 +0000, The Natural Philosopher
wrote:

Or you ,might even cobble together a way of detecting mains (say an
optical isolator fed from the mains) on some sort of I/O pin.

My bro (electronics degree) said re another kind of sensor that I
could create to sense mains electricity flowing would be just by
winding some coils of wire around the mains cable, which would
generate a small voltage when the mains is on or nothing when it's
off. This could then be fed to the RPi or to a Basic Stamp, with
suitable amplification of the signal as necessary.

But the RPi would need to be powered from batteries :-)

On Tue, 7 Jan 2014 08:59:23 -0000, "Brian Gaff"
wrote:

Dunno but does it matter how long?

Well, yeah, if we're talking about the freezer, which is the only
reason why I'd need the gizmo. If power went off continuously for a
number of hours, that would be nice to know later. The neighbour said
it went off for 10 hours just before Christmas. 10 hours, though,
should be okay for the freezer contents, especially given that I only
had minimal heating on so the house would have been cold already.

On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)


I have a bog-standard Netgear router which logs (amongst other things)
startup events. That would show unexpected startups caused by power cuts.

We have a slightly sensitive RCD which very occasionally trips for no
obvious reason. When we go on holiday I set the server at work to ping
my router hourly (address obtained via DynDNS as I don't have static IP)
and to send an SMS text to me and a neighbour with keys if it doesn't
get a response for a while. That has saved the freezer contents and
tropical aquarium fish.


--
Reentrant

On 07/01/2014 09:35, Reentrant wrote:
On 06/01/2014 18:05, . wrote:
I asked the next-door neighbour on return, but it would be really cool
to have a gizmo to plug into the mains, then light an LED if the power
goes out, e.g. in a storm. A more sophisticated version would also say
how long the power was out, e.g. 1 LED = 1 hour, 2 LEDs 2 hours and so
on. Obviously, it would need a battery to keep the LEDs lighted if the
power went off. Does something like this exist already? (Yes, I've
Googled!)


I have a bog-standard Netgear router which logs (amongst other things)
startup events. That would show unexpected startups caused by power cuts.

We have a slightly sensitive RCD which very occasionally trips for no
obvious reason. When we go on holiday I set the server at work to ping
my router hourly (address obtained via DynDNS as I don't have static IP)
and to send an SMS text to me and a neighbour with keys if it doesn't
get a response for a while. That has saved the freezer contents and
tropical aquarium fish.


My oven and microwave clock tell me if there has been a power cut, but
both can only count to one. They simply have to be reset when the
elecrickkery returns!

On Tue, 07 Jan 2014 09:29:03 +0000
.. wrote:

On Tue, 7 Jan 2014 08:59:23 -0000, "Brian Gaff"
wrote:

Dunno but does it matter how long?

Well, yeah, if we're talking about the freezer, which is the only
reason why I'd need the gizmo. If power went off continuously for a
number of hours, that would be nice to know later. The neighbour said
it went off for 10 hours just before Christmas. 10 hours, though,
should be okay for the freezer contents, especially given that I only
had minimal heating on so the house would have been cold already.

Turn a full 'fridge ice tray upside down, and put it on top of the
freezer contents. If it still has ice cubes in it when you return, then
there was no power problem. If it's empty, then there was.

--
Davey.

On 07/01/14 09:24, . wrote:
On Tue, 07 Jan 2014 08:53:35 +0000, The Natural Philosopher
wrote:

Or you ,might even cobble together a way of detecting mains (say an
optical isolator fed from the mains) on some sort of I/O pin.

My bro (electronics degree) said re another kind of sensor that I
could create to sense mains electricity flowing would be just by
winding some coils of wire around the mains cable, which would
generate a small voltage when the mains is on or nothing when it's
off. This could then be fed to the RPi or to a Basic Stamp, with
suitable amplification of the signal as necessary.

thats possible too.

but it is a bit prone to false positives from RF in not dine carefully

a simple resistors full wave bridge and capacitor to an LED with an
optodetector on it is a cheap small and easily constructe in a mains
plug with a two wire socket on it to take a basic 'open collector'
signal back.


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

On 07/01/14 09:28, Andrew May wrote:
On 07/01/2014 09:24, . wrote:
On Tue, 07 Jan 2014 08:53:35 +0000, The Natural Philosopher
wrote:

Or you ,might even cobble together a way of detecting mains (say an
optical isolator fed from the mains) on some sort of I/O pin.

My bro (electronics degree) said re another kind of sensor that I
could create to sense mains electricity flowing would be just by
winding some coils of wire around the mains cable, which would
generate a small voltage when the mains is on or nothing when it's
off. This could then be fed to the RPi or to a Basic Stamp, with
suitable amplification of the signal as necessary.

But the RPi would need to be powered from batteries :-)

I'd use a diode and a resistor and a small battery charge to run it off
rechargeables


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

On Tue, 07 Jan 2014 09:28:12 +0000, Andrew May
wrote:

On 07/01/2014 09:24, . wrote:
On Tue, 07 Jan 2014 08:53:35 +0000, The Natural Philosopher
wrote:

Or you ,might even cobble together a way of detecting mains (say an
optical isolator fed from the mains) on some sort of I/O pin.

My bro (electronics degree) said re another kind of sensor that I
could create to sense mains electricity flowing would be just by
winding some coils of wire around the mains cable, which would
generate a small voltage when the mains is on or nothing when it's
off. This could then be fed to the RPi or to a Basic Stamp, with
suitable amplification of the signal as necessary.

But the RPi would need to be powered from batteries :-)

Not a problem. The Haynes book Raspberry Pi Owner's Workshop Manual
explains how this can be achieved.

On Tue, 7 Jan 2014 12:08:19 +0000, Davey
wrote:

On Tue, 07 Jan 2014 09:29:03 +0000
. wrote:

On Tue, 7 Jan 2014 08:59:23 -0000, "Brian Gaff"
wrote:

Dunno but does it matter how long?

Well, yeah, if we're talking about the freezer, which is the only
reason why I'd need the gizmo. If power went off continuously for a
number of hours, that would be nice to know later. The neighbour said
it went off for 10 hours just before Christmas. 10 hours, though,
should be okay for the freezer contents, especially given that I only
had minimal heating on so the house would have been cold already.

Turn a full 'fridge ice tray upside down, and put it on top of the
freezer contents. If it still has ice cubes in it when you return, then
there was no power problem. If it's empty, then there was.

Yeah, I know the coin trick on top of a frozen glass of water, too!
But it ain't exactly what I'd call a gizmo!

On Tue, 07 Jan 2014 17:21:06 +0000
.. wrote:

On Tue, 7 Jan 2014 12:08:19 +0000, Davey
wrote:

On Tue, 07 Jan 2014 09:29:03 +0000
. wrote:

On Tue, 7 Jan 2014 08:59:23 -0000, "Brian Gaff"
wrote:

Dunno but does it matter how long?

Well, yeah, if we're talking about the freezer, which is the only
reason why I'd need the gizmo. If power went off continuously for a
number of hours, that would be nice to know later. The neighbour
said it went off for 10 hours just before Christmas. 10 hours,
though, should be okay for the freezer contents, especially given
that I only had minimal heating on so the house would have been
cold already.

Turn a full 'fridge ice tray upside down, and put it on top of the
freezer contents. If it still has ice cubes in it when you return,
then there was no power problem. If it's empty, then there was.

Yeah, I know the coin trick on top of a frozen glass of water, too!
But it ain't exactly what I'd call a gizmo!

Why look for a gizmo, when there are simple solutions available? Just
to look geeky?

--
Davey.

On Tuesday, January 7, 2014 1:59:43 PM UTC, The Natural Philosopher wrote:
On 07/01/14 09:24, . wrote:
On Tue, 07 Jan 2014 08:53:35 +0000, The Natural Philosopher
wrote:

Or you ,might even cobble together a way of detecting mains (say an
optical isolator fed from the mains) on some sort of I/O pin.

My bro (electronics degree) said re another kind of sensor that I
could create to sense mains electricity flowing would be just by
winding some coils of wire around the mains cable, which would
generate a small voltage when the mains is on or nothing when it's
off. This could then be fed to the RPi or to a Basic Stamp, with
suitable amplification of the signal as necessary.

thats possible too.
but it is a bit prone to false positives from RF in not dine carefully
a simple resistors full wave bridge and capacitor to an LED with an
optodetector on it is a cheap small and easily constructe in a mains
plug with a two wire socket on it to take a basic 'open collector'
signal back.

Or just a Class Y cap


NT

On Tue, 7 Jan 2014 21:09:52 +0000, Davey
wrote:

Why look for a gizmo, when there are simple solutions available? Just
to look geeky?

That's what a million people said about any invention before it caught
on.