Author Topic: Alarm for electric circuit failure  (Read 1135 times)

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Alarm for electric circuit failure
« on: February 10, 2019, 12:05:03 pm »
There's a property with an underground stream running through its cellar. The stream enters at one side, runs in a channel around the walls and exits through an opening in the opposite wall. Nobody has been able to determine precisely where it rises or runs to (it certainly doesn't flow into the storm drain as it's below their level). Most of the time it doesn't cause any problems but there's a pump, activated by a float switch, to keep it at a manageable level. The problem is that various people have use of the building and there have been occasions when someone has turned the pump off (presumably thinking it was a waste of power), leading to a cellar waist-deep in water. Power cuts are also an obvious worry.

So what we want is an alarm to show if the pump is not receiving power for whatever reason. I suggested some sort of voltage sensor but it's hardly my area of expertise, so I'm asking here. It obviously needs an independent power supply, presumably a battery, so it can go off in the event of a power cut.
An ungovernable laughter, a joyous agitation which makes the summer stretching before you seem like an unrolling canvas on which you might draw those first rude pure strokes that are free. (Capote)

Kim

  • 2nd in the world
Re: Alarm for electric circuit failure
« Reply #1 on: February 10, 2019, 02:06:56 pm »
Commercial products to do exactly this exist:  Google for "power failure alarm".

Or roll your own:  Long-life battery, suitable noise-making-device, normally-closed relay.  Power the coil of the relay from a wall-wart.

Some sort of water-level-higher-than-the-pump-should-be-keeping-it alarm might also be a valid approach:  Not as quick to respond to power failure, but would warn if the pump stopped working effectively for other reasons (eg. due to blockages or overwhelming water).

Wiring the pump up in such a way that compulsive switcher-offers can't easily access it (eg. into an unswitched fused spur) might also help...
To ride the Windcheetah, first, you must embrace the cantilever...

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Alarm for electric circuit failure
« Reply #2 on: February 10, 2019, 02:21:05 pm »
Thanks. Problem though, which has just occurred to me: I'm not sure there are any electric sockets in the cellar. Though I'm sure we could easily get one put in, it's just it has to go through various approval procedures (due to the ownership structure of this building), which would be no problem to get but take time.
An ungovernable laughter, a joyous agitation which makes the summer stretching before you seem like an unrolling canvas on which you might draw those first rude pure strokes that are free. (Capote)

Re: Alarm for electric circuit failure
« Reply #3 on: February 10, 2019, 03:41:45 pm »
The water level sensor option is a good one, there are commercial sensors that are basically a pair of wires with bare ends. The water rising bridges them and completes a (low voltage or “volt free”) circuit that sounds an alarm. Won’t work in power cuts (unless back-up battery powered) but then neither will the pump.
We are making a New World (Paul Nash, 1918)

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Alarm for electric circuit failure
« Reply #4 on: February 10, 2019, 04:04:44 pm »
Well, that's the other problem: if the pump fails at a time of eg high rain, a back-up plan is needed (a big bucket!).
An ungovernable laughter, a joyous agitation which makes the summer stretching before you seem like an unrolling canvas on which you might draw those first rude pure strokes that are free. (Capote)

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Alarm for electric circuit failure
« Reply #5 on: February 10, 2019, 04:11:04 pm »
Commercial products to do exactly this exist:  Google for "power failure alarm".

Or roll your own:  Long-life battery, suitable noise-making-device, normally-closed relay.  Power the coil of the relay from a wall-wart.
Just checking I understand how this works: Mains power keeps the relay open (not completed). When mains power fails, the relay closes and completes the circuit, sending power from batter to alarm. At least that's the only way it makes sense to me, but the term "normally-closed" is not entirely clear to me.
An ungovernable laughter, a joyous agitation which makes the summer stretching before you seem like an unrolling canvas on which you might draw those first rude pure strokes that are free. (Capote)

Re: Alarm for electric circuit failure
« Reply #6 on: February 10, 2019, 07:31:39 pm »
Commercial products to do exactly this exist:  Google for "power failure alarm".

Or roll your own:  Long-life battery, suitable noise-making-device, normally-closed relay.  Power the coil of the relay from a wall-wart.
Just checking I understand how this works: Mains power keeps the relay open (not completed). When mains power fails, the relay closes and completes the circuit, sending power from batter to alarm. At least that's the only way it makes sense to me, but the term "normally-closed" is not entirely clear to me.

I think you have it right.

Relay contacts can be "normally-open" where they are "open", or not conducting, "normally", or when there isn't power on the coil.

Or they can be "normally-closed" where they are "closed", or conducting, "normally", or when there isn't power on the coil.

Kim has suggested the latter, normally-closed, so it will conduct and sound the alarm when there isn't power on the coil.

For details, use a wall-wart that supplies 12 V.  Any old and unused 12 V router power supply will do, or one of these:-
https://www.ebay.co.uk/itm/AC-100-240V-to-DC-12V-Power-Supply-Converter-Adapter-Charger-Transformer-UK-Plug/392189151864?hash=item5b504b8a78:g:ocIAAOSwUP5cCzlf:rk:12:pf:0 if you can't find one in your dead router box.

Wire that to a 5 pin automotive relay, such as this:-
https://www.ebay.co.uk/itm/12V-DC-40A-30A-5-Pin-Relay-Automotive-Changeover-Car-Bike-Boat-Switch/201944673743?hash=item2f04d72dcf:m:mVa8o5Q27MeNkmKe5spoq0A:rk:8:pf:0

Those have 5 terminals numbered 85, 86, 87, 30 and 87a. Wire the 12 V wall wart to terminals 85 and 86, either way round. That will click when you plug in the power supply, and will click more quietly, a short time after you unplug.

Now wire a battery to a buzzer and put the relay in to break the circuit, wiring to terminals 20 and 87a, either way round. Make no connection to terminal 87. It should buzz when the power supply is unplugged, and be silent when the power supply is plugged in.
Quote from: Kim
Paging Diver300.  Diver300 to the GSM Trimphone, please...

Re: Alarm for electric circuit failure
« Reply #7 on: February 10, 2019, 08:17:37 pm »
The water level alarm could be engineered to run for several years from a battery.

Re: Alarm for electric circuit failure
« Reply #8 on: February 11, 2019, 10:43:48 am »
The water level alarm could be engineered to run for several years from a battery.

Indeed, actually all that is needed is a battery, a bulb (or several if you like), and wire in a loop, with the loop broken by two bare ends of wire at a suitable level. Water rises, completes circuit, bulb(s) light(s). Low self-discharge battery and LED bulb(s). Could even use a gel motorcycle battery on a trickle charger.
We are making a New World (Paul Nash, 1918)

Re: Alarm for electric circuit failure
« Reply #9 on: February 11, 2019, 11:28:56 am »
IANAEE (I'm sure one will be along shortly), but I cannot see how that would work. Surely the resistance of water is much greater than that of a bulb so the PD across the bulb would be tiny?
Quote from: tiermat
that's not science, it's semantics.

Kim

  • 2nd in the world
Re: Alarm for electric circuit failure
« Reply #10 on: February 11, 2019, 11:43:34 am »
IANAEE (I'm sure one will be along shortly), but I cannot see how that would work. Surely the resistance of water is much greater than that of a bulb so the PD across the bulb would be tiny?

If the bulb were an LED it would light with a couple of milliamps, but for any real load you'd need to amplify the current with an op-amp or darlington pair or whatever.
To ride the Windcheetah, first, you must embrace the cantilever...

Re: Alarm for electric circuit failure
« Reply #11 on: February 11, 2019, 11:52:03 am »
Pure water has a very high resistance (18Mohms is the generally accepted value) , but groundwater not so much. Far too many impurities.
We are making a New World (Paul Nash, 1918)

Kim

  • 2nd in the world
Re: Alarm for electric circuit failure
« Reply #12 on: February 11, 2019, 12:01:55 pm »
Commercial products to do exactly this exist:  Google for "power failure alarm".

Or roll your own:  Long-life battery, suitable noise-making-device, normally-closed relay.  Power the coil of the relay from a wall-wart.
Just checking I understand how this works: Mains power keeps the relay open (not completed). When mains power fails, the relay closes and completes the circuit, sending power from batter to alarm. At least that's the only way it makes sense to me, but the term "normally-closed" is not entirely clear to me.

I think you have it right.

Relay contacts can be "normally-open" where they are "open", or not conducting, "normally", or when there isn't power on the coil.

Or they can be "normally-closed" where they are "closed", or conducting, "normally", or when there isn't power on the coil.

Kim has suggested the latter, normally-closed, so it will conduct and sound the alarm when there isn't power on the coil.

For details, use a wall-wart that supplies 12 V.  Any old and unused 12 V router power supply will do, or one of these:-
https://www.ebay.co.uk/itm/AC-100-240V-to-DC-12V-Power-Supply-Converter-Adapter-Charger-Transformer-UK-Plug/392189151864?hash=item5b504b8a78:g:ocIAAOSwUP5cCzlf:rk:12:pf:0 if you can't find one in your dead router box.

Wire that to a 5 pin automotive relay, such as this:-
https://www.ebay.co.uk/itm/12V-DC-40A-30A-5-Pin-Relay-Automotive-Changeover-Car-Bike-Boat-Switch/201944673743?hash=item2f04d72dcf:m:mVa8o5Q27MeNkmKe5spoq0A:rk:8:pf:0

Those have 5 terminals numbered 85, 86, 87, 30 and 87a. Wire the 12 V wall wart to terminals 85 and 86, either way round. That will click when you plug in the power supply, and will click more quietly, a short time after you unplug.

Now wire a battery to a buzzer and put the relay in to break the circuit, wiring to terminals 20 and 87a, either way round. Make no connection to terminal 87. It should buzz when the power supply is unplugged, and be silent when the power supply is plugged in.

My thoughts exactly.

Obviously there are ways to do this more efficiently without keeping a relay coil active all the time, but there's a certain appeal to the KISS approach and parts that are easily scrounged.

Related, thoroughly obsolete, advice:  You can add monitoring to a 'dumb' UPS by plugging a convenient modem into the un-maintained supply and monitoring the DSR pin.
To ride the Windcheetah, first, you must embrace the cantilever...

Re: Alarm for electric circuit failure
« Reply #13 on: February 11, 2019, 12:17:25 pm »
Problem though, which has just occurred to me: I'm not sure there are any electric sockets in the cellar. Though I'm sure we could easily get one put in, ...

I like to think that putting a mains socket in a room which routinely floods might not be so easy  :o

Also, given that the switch gets switched by people that don't know it's importance; what will happen when a light or buzzer goes at someone that doesn't know it's importance? How often is it seen by someone in the know?

So, I'd favour the "replace the switch with something that needs tools to switch" approach to making sure the pump has power.

Then maybe a webcam / twitter feed?

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Alarm for electric circuit failure
« Reply #14 on: February 11, 2019, 12:23:27 pm »
It doesn't routinely flood. The only incident I'm aware of was when the pump got switched off for a week. Though what was in place when the building was built (about 1905) I don't know. Would be good to find out, in fact. But the same had occurred to me re mains sockets and floods.

We'd have a light rather than an audible alarm, partly to avoid getting confused with a fire alarm (there can be random people in the building), something like twitter feed or text alert too.
An ungovernable laughter, a joyous agitation which makes the summer stretching before you seem like an unrolling canvas on which you might draw those first rude pure strokes that are free. (Capote)

Re: Alarm for electric circuit failure
« Reply #15 on: February 11, 2019, 12:24:16 pm »
Put in a lockable isolator?
We are making a New World (Paul Nash, 1918)

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Alarm for electric circuit failure
« Reply #16 on: February 11, 2019, 12:27:52 pm »
An ungovernable laughter, a joyous agitation which makes the summer stretching before you seem like an unrolling canvas on which you might draw those first rude pure strokes that are free. (Capote)

Re: Alarm for electric circuit failure
« Reply #17 on: February 11, 2019, 12:48:12 pm »
As a water industry engineer there are various ways of achieving these ideas.

Firstly the level switch; this can either be level probes such as the bare wires method mentioned but rather safer. a google for water level probes will return a number of models for these. The alternative is a float switch, basically a float hanging from a pivot, when the water level rises the weight of the float is taken off the pivot and the circuit is closed.

Secondly the pump; depending on the pump and the supplier there may already be internal circuits in the pump to give statuses such as running, fault etc. These will be contacts on the pump that will complete a circuit in specific circumstances, like healthy or running. If you know the pump manufacturer and model it may be possible that you only need a small box with a couple of lamps, to display what the pump is already saying.

Re: Alarm for electric circuit failure
« Reply #18 on: February 11, 2019, 12:55:12 pm »
As a water industry engineer there are various ways of achieving these ideas.

Firstly the level switch; this can either be level probes such as the bare wires method mentioned but rather safer. a google for water level probes will return a number of models for these. The alternative is a float switch, basically a float hanging from a pivot, when the water level rises the weight of the float is taken off the pivot and the circuit is closed.


We used to use the Mowbray float switches, but they need (I suspect) too grate a (change in) water level for a basement application, hence the mention of probe types.

Ah, which reminds me - I'm too long out of the business to remember, but there is/was a type of float switch like a small ball-cock float on the end of a probe - perhaps your more up-to-date experience will recall them?
We are making a New World (Paul Nash, 1918)

Kim

  • 2nd in the world
Re: Alarm for electric circuit failure
« Reply #19 on: February 11, 2019, 12:59:05 pm »
Put in a lockable isolator?
Good idea.

And maybe even sign saying "Power to sump pump - if you switch this off the building will flood."  Not that compulsive switcher-offers are affected by mere signs, but it might stop someone randomly poking around for a light switch.
To ride the Windcheetah, first, you must embrace the cantilever...

Re: Alarm for electric circuit failure
« Reply #20 on: February 11, 2019, 01:07:49 pm »
As a water industry engineer there are various ways of achieving these ideas.

Firstly the level switch; this can either be level probes such as the bare wires method mentioned but rather safer. a google for water level probes will return a number of models for these. The alternative is a float switch, basically a float hanging from a pivot, when the water level rises the weight of the float is taken off the pivot and the circuit is closed.


We used to use the Mowbray float switches, but they need (I suspect) too grate a (change in) water level for a basement application, hence the mention of probe types.

Ah, which reminds me - I'm too long out of the business to remember, but there is/was a type of float switch like a small ball-cock float on the end of a probe - perhaps your more up-to-date experience will recall them?

I believe I have come across such as these however they are more normally used where you want to keep a tank full. The float switch on a cable is most often used to stop a pump in the event that a tank is too empty where the depth from the access and mounting of the floats to the water level you want to measure is too long for probes.

The issue being that the housing for the probes needs to be mounted above the top water level as the casings don't like to be submerged but the tips need to be below the level you want to measure.

* Additional background*

I am a process engineer so I tend to define the size of tanks and the levels the tanks operate at but leave detecting these levels and the choice of instrument to the ICA (Instrumentation, Control and Automation) specialists.

Re: Alarm for electric circuit failure
« Reply #21 on: February 11, 2019, 01:12:36 pm »
Should have been clearer, the Mowbrays have two floats, and we used them as stop / start for tank filling.  Low level gives the weight of both floats to pull the switch for refill, then as level rises and load comes off as both float the switch turns off the pump. You need at least 1m depth to get them to work tho.
We are making a New World (Paul Nash, 1918)

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Alarm for electric circuit failure
« Reply #22 on: February 11, 2019, 01:37:50 pm »
As a water industry engineer there are various ways of achieving these ideas.

Firstly the level switch; this can either be level probes such as the bare wires method mentioned but rather safer. a google for water level probes will return a number of models for these. The alternative is a float switch, basically a float hanging from a pivot, when the water level rises the weight of the float is taken off the pivot and the circuit is closed.

Secondly the pump; depending on the pump and the supplier there may already be internal circuits in the pump to give statuses such as running, fault etc. These will be contacts on the pump that will complete a circuit in specific circumstances, like healthy or running. If you know the pump manufacturer and model it may be possible that you only need a small box with a couple of lamps, to display what the pump is already saying.
Thanks, Matthew. So it might simply be a case of contacting the pump manufacturer to find out. Should've thought of that ourselves!
An ungovernable laughter, a joyous agitation which makes the summer stretching before you seem like an unrolling canvas on which you might draw those first rude pure strokes that are free. (Capote)

Re: Alarm for electric circuit failure
« Reply #23 on: February 11, 2019, 02:36:54 pm »
As a water industry engineer there are various ways of achieving these ideas.

Firstly the level switch; this can either be level probes such as the bare wires method mentioned but rather safer. a google for water level probes will return a number of models for these. The alternative is a float switch, basically a float hanging from a pivot, when the water level rises the weight of the float is taken off the pivot and the circuit is closed.

Secondly the pump; depending on the pump and the supplier there may already be internal circuits in the pump to give statuses such as running, fault etc. These will be contacts on the pump that will complete a circuit in specific circumstances, like healthy or running. If you know the pump manufacturer and model it may be possible that you only need a small box with a couple of lamps, to display what the pump is already saying.
Thanks, Matthew. So it might simply be a case of contacting the pump manufacturer to find out. Should've thought of that ourselves!

Equally you said the pump has a float switch so that it starts automatically, there is a good chance that the pump will have a set of contacts to say the float switch is calling the pump to run (also means the water is high). Normally these contacts would be wired back to a control system that would then light lamps or display on a screen what the pump is doing. It all depends on how big and complex the pump is.

Most of the pump manufacturers will have a manual online which will include a wiring diagram so just the manufacturer and model will allow others here to advise. PM me the pump details if you want.

Vince

  • Can't climb; won't climb
Re: Alarm for electric circuit failure
« Reply #24 on: February 11, 2019, 06:08:30 pm »
Do UPSs have alarms when they are running from battery power?

If so run the pump from a UPS so you are covered for power cuts too.
216km from Marsh Gibbon