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Alarm outage with reset switch.

Baihakee

New Member
Hi everyone, can you help me

I want to make a alarm circuit when the power failure or outage. Relay detect a 220vac in normal close, so when 220vac it’s fail , relay can detect and buzzer is alarm until press a reset switch.8DB3E0E6-CA12-4E52-AC24-5368D5EA3BC1.png
 

gophert

Well-Known Member
Most Helpful Member
Wire a relay so the normally-closed circuit sounds your alarm, as you have drawn.
- make sure to get a relay that can handle 100% duty cycle (most can)
- make sure the relay's coil can handle your AC line voltage. Or use a USB-type charger (5vdc) and get a relay with 5vdc coil voltage.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
The circuit you posted would work fine for that.

Aside
I put a drop-out relay in an outlet strip once. You plug it in and press reset. When the power dropped out and came back the relay would stay de-energized. I'd plug an auto-answer modem into it. I could call the lab phone and if it didn't answer, we had a power failure.
I coould then goto work and reset the I-V-t overnight measurement.
 
Last edited:

Nigel Goodwin

Super Moderator
Most Helpful Member
The circuit you posted would work fine for that.

Aside
I put a drop-out relay in an outlet strip once. You plug it in and press reset. When the power dropped out and came back the relay would stay de-energized. I'd plug an auto-answer modem into it. I could call the lab phone and if it didn't answer, we had a power failure.
I coould then goto work and reset the I-V-t overnight measurement.
A VERY time ago I wired a 240V DPDT AC relay among my household fuse boxes (following a little reorganisation of which fuseboxes fed where) - so that particular fusebox feeds all the lights, the central heating boiler electronics, and the circuit that feeds the TV etc. The relay is wired so that while the normal mains is working the relay feeds the mains straight through to that fusebox - but if the mains drops out, the relay also drops out and connects that fusebox to a 2KW generator instead.

You have to manually start the generator (which won't start any more!), and once the mains comes back ON the relay flicks back over, disconnecting the generator and restoring normal mains feed. This means that it's pretty fail safe - you don't want both mains and generator trying to feed at the same time, or the generator trying to feed back out to the grid.
 

Baihakee

New Member
I want to hold LED stay on, even though SW1 it's close.
in this schematic, LED off when main power (SW1) is a closed circuit.

thankyou

1588521210718.jpg
 

eTech

Well-Known Member
Here's one alternative.

1. When AC is present:
PWR is energized
C1 is charged
ALMR is deenergized
LED is off
Buzzer is off

2. When AC is removed:
PWR is deenergized
C1 discharges thru ALMR
ALMR is energized
LED is on
Buzzer is on

3. When AC is removed and RESET button is pressed:
PWR is deenergized
C1 remains discharged thru ALMR
ALMR is deenergized
LED is off
Buzzer is off

4. When AC is restored:
Return to state 1.

1588525083905.png
 
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