Project - Delphijustin industries https://delphijustin.biz Making use out of things! Mon, 27 Jun 2022 22:41:03 +0000 en-US hourly 1 https://wordpress.org/?v=6.2.9 https://delphijustin.biz/wp-content/uploads/2025/10/cropped-dongwa-192-32x32.png Project - Delphijustin industries https://delphijustin.biz 32 32 Simple doorbell/alarm https://delphijustin.biz/simple-doorbell-alarm/?utm_source=rss&utm_medium=rss&utm_campaign=simple-doorbell-alarm https://delphijustin.biz/simple-doorbell-alarm/#respond Fri, 17 Jun 2022 15:57:15 +0000 https://delphijustin.biz/?p=4160 This is probably the simplest doorbell or alarm circuit that is out there. The buzzer will not be constantly on since the buzzer gets switched on by a capacitor. The circuit draws hardly anything when off as you will see in the graph below. As the capacitor gets charged its current lowers down a lot. …

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]]> This is probably the simplest doorbell or alarm circuit that is out there. The buzzer will not be constantly on since the buzzer gets switched on by a capacitor. The circuit draws hardly anything when off as you will see in the graph below. As the capacitor gets charged its current lowers down a lot. If you want to save money for parts and use a power supply use the one with the relay. The relay will make it work with a spst switch. I wish I knew that before ordering the parts

It uses a switching transistor to turn the buzzer on and off. It’s best to use a transistor since it can take very little current to turn on. It needs a SPDT magnet alarm switch since it has to switch the capacitor between +v and transistor base resistor. You cannot use a SPST switch. I didn’t need a transistor for the buzzer since it didn’t need alot of current.

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