I have got a fused feed in the shed at the bottom of the garden with a freezer in it and last week the fuse tripped and the freezer was off but it only must have been a few hours ...now what Ineed is some type of alarm to let me know when this happens so the freezer does not be off for days without noticing.
Power failure alarm
- Thread starter JOHNBOY42
- Start date
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You need a relay with a mains coil and a low voltage normally closed contact. Put the relay in a box, connect a length of mains lead to the coil, earth the box if it's a metal one and put a mains plug on the other end. Plug it into a socket on the same circuit as the freezer. If the power goes off the contact will close.
You can now use that relay contact to control a bell - or any other kind of alarm you like - in the house. Treat it just like a bell-push.
For improved safety, connect one side of the relay contact to mains earth.
This is not a fail-safe circuit. It will fail if somebody breaks the low voltage wire between the shed and the house. For improved integrity you need a relay with a changeover contact. Connect all three terminals of this CO contact through 3-core wire back to the house. You now have access to the original NO contact and also an NC contact at the house end. Use the NC contact as you did before and the NO contact to control a second relay. This one has an NC contact which, when all is well, will be held open. Use that in parallel with the one in the shed to switch the bell. If you're any good at electronics you can do all the house end stuff with logic circuits.
PS: By now you might be wondering what will happen if the bell fails. How will you know? To get round this you will need the Sellafield solution. Their alarms sound continuously unless there's a problem. If they stop, you run!
You can now use that relay contact to control a bell - or any other kind of alarm you like - in the house. Treat it just like a bell-push.
For improved safety, connect one side of the relay contact to mains earth.This is not a fail-safe circuit. It will fail if somebody breaks the low voltage wire between the shed and the house. For improved integrity you need a relay with a changeover contact. Connect all three terminals of this CO contact through 3-core wire back to the house. You now have access to the original NO contact and also an NC contact at the house end. Use the NC contact as you did before and the NO contact to control a second relay. This one has an NC contact which, when all is well, will be held open. Use that in parallel with the one in the shed to switch the bell. If you're any good at electronics you can do all the house end stuff with logic circuits.
PS: By now you might be wondering what will happen if the bell fails. How will you know?
To get round this you will need the Sellafield solution. Their alarms sound continuously unless there's a problem. If they stop, you run!
B
breezer
dont connect any part of the relay to eath and you dont need a 2nd relay.
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B
breezer
There is or was a plug for freezers (i had one may years ago) but even if you can still get them, not a lot of use in your case.
put it this way fart, and wind tunnel
in other words you will not be able to her the buzzer in the house with the buzzer in the shed.
a light will be of no use what so ever since you can't hear a light
put it this way fart, and wind tunnel
in other words you will not be able to her the buzzer in the house with the buzzer in the shed.
a light will be of no use what so ever since you can't hear a light
B
breezer
not if you are asleep you wont see a light.
as i said, IF you can get a plug with a buzzer in it you will not be able to hear it, they only had small buzzers.
You really will have to go down the relay route I am afraid to say.
as i said, IF you can get a plug with a buzzer in it you will not be able to hear it, they only had small buzzers.
You really will have to go down the relay route I am afraid to say.
S
saxondale
madness, the cable has to feed from the house to the shed - something on the house side then? but I really don`t like the idea of home made relay boards.
B
breezer
how do you figure that one?
The mains supply has to come from the same supply that runs the freezer, if it doesnt it defeats the object of the exercsie.
no boards are required, just a relay
unless you can come up with an off the shelf alternative the OP has no choice other than to diy
S
saxondale
obviously - so unless the shed is off its own power station the cable TO the shed must come from within the house - so put the buzzer / light / device on this cable inside the house and you overcome the problem of not hearing it ?
relay cant live on its own - quick google will find mains fail indicators
B
breezer
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Just plug one of those low wattage bulbs into a lamp holder -say 6 watts and plug it into a double socket with the freezer. It'll be on as long as the freezer is on and will cost about £2 per year to run. You can see it from your lounge if it goes off....
B
breezer
novel idea, but i think the OP wants to hear something, problem with a light (apart from you cant hear it, so of no use if OP is asleep) you have to remember to look at it, and also in a bright day you may not be able to see it.
S
saxondale
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