Power Loss Alarm System

Very easy to make one for a few quid ...

http://www.electronics-project-design.com/PowerFailureAlarm.html

... but maybe not a good idea messing with mains if you're not sure what you're doing.

Thanks JohnDG

I'm not an electronics expert, but I have downloaded a schematic that I can use to build such a device before I asked the question. I am an electrician, so I am happy to "mess with mains".

Perhaps you could e-mail me your idea for a schematic and I will check this against the schematic I already have?

Hi again JohnDG

Didn't realise you had placed the web address of the site you wanted me to look at (apologies). Yes, that is the circuit I had already found, so I will try to get a local company to build me a trial model of it. Thanks again for you time.

I like JohnDG"s approach. But, did you ever consider tearing up a smoke detector and using those parts?

Thank you Lynlynch.

I have already looked inside a wired alarm but as I am an electrician and not an electronics expert I don't want to rip apart items that will be connected to the mains without knowing exactly what I am doing. Therefore, I intend to ask an electronics team in my area to see if they can build me one. Thanks for your (and everyone's) help though.

Here in the UK we have the new 17th wiring rules, and that is forcing all new electrics to be routed via an rcd or rcbo, so when a freezer is on the main household circuit (or on another circuit protected by an rcd) a "trip" causes the power loss. If the freezer power is on a separate circuit and the freezer is in the garage the owner may not realise until too late. Hence I think that a cheap version of this alarm (as it doesn't seem to be available at the moment) will sell well.

These answers are great, but complicated. Take a wall transformer that turns a/c into low voltage dc and a nail and make a simple electromagnet.mount your electromagnet so it holds up a contact piece that when dropped will close an open connection between the alarm battery and the alarm. or rig somthing that would work like the old point system on a car distributor,just without the tension spring holding them apart turn it upright and just use the magnetics to seperate and gravity to close the connection. I could make one for under $5, about $1.00 with used parts,the transformer costing 50 cents or less at a yard sale.If your going to sell them, i would like in on the construction. There are several ways to make this device,you could even add a clock that starts at 12, and lets you know how long your power has been out. You could stick an outside switch on it so you could shut the alarm off when you came to check on it without unplugging it. If the power came back on, the alarm would cease. yes, the same transformer could be used to keep a battery charged up for the alarm,and it would be easy to hook in a few led lights,as well. The 110volta/c led lightsyou get as christmas light sets work very well on low voltage dc if you cut up the light set into individual bulbs,most use between 3-4 vdc each

Thank you "ageniusforhire"

That is so simple and effective, I'm sure I can do something with these ideas.

Thank you all for your excellent ideas. This is a great forum.

Maybe plug a low-watt LED into the outlet next to the refrigerator outlet? Light = power available; dark = power outage (or burned-out LED).

http://www.thermoworks.com/products/low_cost/rt801.htmltry;

Welcome to ThermoWorks View My Account Login / Register Products What's NEW Thermapens NEW Splash-Proof Original Super-Fast High-Accuracy Other Types Infrared Meters Low Cost Digitals Handheld Meters Waterproof Meters Panel Meters Probes & Sensors Thermocouples Platinum RTD's Data Loggers, Recorders, Printers, HACCP Loggers Calibration Gear Lab Baths & Circulators Dial & "Other" Thermometers Timers Humidity Instruments Accessories pH Instruments Software Pelican/Storm Cases Office Hours: M-F 8 am to 5 pm MST Canada & International

$19.00 RT801 Digital Fridge/Freezer Alarm Thermometer Range -58 to 158°F °C / °F Switchable Display Backlight Settable High/Low Alarm Min/Max Memory Internal and External Temperatures

Hi Big John Mac

That's it!

Thanks for the link

I am buying one right now.

Advantage of temperature monitor (as per #5): cheap'n'cheerful, self-contained, no mains connection.

Disadvantage: Mains power fail alarm would give you a lot more time to get it fixed before food spoilt.

Yes, you are right.

I will probably get the mains power alarm idea built as well (there would be many other uses for this type of alarm)

Thanks JohnDG (and everyone else) for your time

Dont get too carried away with the "other uses" for this type of circuit closer.I am sure you could find yourself in a heap of trouble if you became mischevious.lol. it can also be rigged up to make the connection when power comes on,lol.

Thanks Tornado

Yes, in the UK we usually fit a freezer to the power circuit using a fused switch that has an incorporated LED. The reason for an audible alarm is for those customers that have a big chest freezer in the garage. Power loss not noticed in time = loss of frozen food and a bill or insurance claim to re-stock it all. Also I have heard from two people who didn't notice the LED on the power (fused) switch to their freezer was not "on", and they lost the frozen food contents too. Every customer I have spoken to likes the idea of an audible alarm, even when the freezer is in the kitchen. Hence I am looking to get a trial version built if they truly don't already exist.

Hook up a relay to the power source that has a set of NO (normally open) contacts.

When the power fails the contacts close. You can use this to switch on a bell, light or other annunciator.

In the US I can buy a relay with a socket that has terminal screws on it for less than $10US from a surplus electronic house. The screws make hooking up the bell very easy. Just be sure that the relay coil voltage matches your line voltage. Good luck EdfromNJUSA

Sounds good. Thanks for that advice

Here in the states if You have a commercial building it must be equiped with emergency lighting if there is a power failure. Its a simple device obtainable at any electrical outlet store for about $30.00 (usa). They usualy have 2 lights but I'm sure You could replace one light with a buzzer. Installing one is not brain surgery.

oilcan13

Thanks oilcan13

Another good idea. For people that have a freezer in their garage what better idea than an emergency light... not only warning you the power is off but making sure that you can see where you are going (as garages are full of things you may bump into or trip up on)

You guys are coming up with some great ideas. Well done!

Tilerman,

The freezer should not trip that breaker except under unusual circumstances. Check the starting capacitor and the compressor motor.

Check if there are other loads on the circuit. It is better if the freezer is alone on the breaker. Two inductive loads - motors starting - could trip an otherwise adequate circuit.

Make sure the circuit has heavy enough wiring and a large enough breaker.

An inexpensive way to monitor the breaker is to plug an AC powered smoke alarm into the same circuit. It will start to beep if it looses AC power.

Good luck

Dave

Hi LG Dave

My idea is for when the freezer is on a Consumer Unit line with about four or five other circuits (each protected by an mcb and the whole line protected by an rcd) it's not that the freezer causes a trip but if something else causes a trip and all the circuits on the same rcd line go out at the same time.

But thanks for your time and the good information about freezer faults ... it all helps me to provide customers with the best service possible.

Happy to help.

Good luck.

would the cheap wired in fire alarm be wrong for your situation. Just add a plug,plug it in next to the fridge and voila. you could also make a small electromagnet and run it off a little transformer plugged into the same line.when the transformer lost current,the core could drop a little and close a connection in a circuit with the battery and buzzer.

If you want to go fancy then fit a current monitoring relay and a timer at the board where the freezer is supplied from. The actual sounder circuit would be the same as johnDG's diagram. this way if the freezer doesn't draw current for greater than the preset time then it either has the power cut or it has been unplugged.

Chas

Hi Capblanc

Yes, I thought about getting the companies that supply the Consumer Units to start adding a small (battery powered) alarm to their rcd's and rcbo's to warn of power failure (on protected lines where the loss of power is not so obvious). Most replies were negative, but some offered units to mount into the Consumer Unit. This is the best idea, but often it takes up space on the CU board and in the UK most domestic power supply boards (CU's) are already full up (with mcb's and rcd's etc). So we need a manufacturer that can add an alarm into their rcd units and thereby save space. This is another idea that I am working on.

Thanks for your time

I think LG Dave's answer takes the prize for doing what the OP wants at the most economical cost and off-the-shelf. The smoke detector incorporates a battery (usually 9 VDC transistor radio type) to power the buzzer when the AC goes down. Very straightforward.

I agree, since I posted this situation you have all (kindly) given me some great ideas to give a customer several alternatives.

1. Big John Mac showed me where to buy a commercial thermal alarm (found some in the UK for £15) the simple (ready to buy) answer but slow to warn of power loss.

2. JohnDG's guide towards making a true power loss alarm (worth doing for other situations as well)

3. Oilcan13's idea of joint circuit with an emergency light

4. The idea of combining the circuit with an ac fire alarm (various contributors and again, a worthy alternative)

5. Capblanc's idea of fitting (JohnDG's) current monitoring relay and a timer at the board where the freezer is supplied from (I'll be writing to all manufacturers of CU's to see what they think about getting this done for the future)

6. Ageniusforhire's idea of a wall transformer supplying power to an electromagnet (or electromagnetic switch) … cheap and effective?

All of you guys are coming up with some great ideas. Thank you all for the time taken.

Re the fridge alarm I posted you about: I have cut-and -spliced the wire to lengthen it with no noticible accuracy loss (about 15') and then taped the sensor to my water heater on the output pipe to visually monitor water heat. Of course, there is some small inaccuracy due to losses of tape etc, but at least I get a reference. I do not know how far one could extend it, but think that if wire resistance losses were slight that one might find that useful, as maybe getting meter to a readily observable location. I intend to run it several hundred feet out to my greenhouses soon, so can monitor them from my rocker !!

I agree this unit has many other uses than just a freezer alam.

Thanks for your time