Instructables

Fire Bell Alarm Clock

Picture of Fire Bell Alarm Clock
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There are many ways you could create your own fire bell alarm clock it all depends on what type of alarm clock you are going to use. On the alarm clock I chose there is an led LCD back light and It turns on for about 6 seconds when the alarm goes off so I used that to latch a relay. If you have any questions feel free to ask!
coolstuff14 (author) 8 months ago
I'm sorry the schematic is wrong the side of the relay coil hooked up to the collector of the transistor should be hooked to the first poll on the relay not the 9v. I'm going to upload a new one today.
coolstuff14 (author)  coolstuff148 months ago
Schematic is now correct
snoekie8 months ago
I think the schematic should look something like this
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snoekie8 months ago
I am assuming that once the backlight turns on and the relay switches that the relay's one pole will keep power to the coil of the relay and the button breaks the loop to disable the bell. So the button will be a push-to-break button. In this case the schematic is not correct. If I missed the purpose of the push button and the schematic is indeed correct, there is a direct short from the 9v to gnd
davescz8 months ago
What is the sense of button in circuit ? Does it shortcut the 9V battery or what ?