Self-powered Doorbell

This very simple and self-powered device was conceived to allow a person to monitor if someone has rung his home door-bell when he was out. As most door-bells use 12Vac supply, the circuit must be simply connected to the two door-bell-coil leads. More: Though this device was primarily intended to be used when a person leaves the house for a few hours or a week-end, a number of tests has proven that a minimum of 15 days "memory" can be guaranteed, even using cheap capacitor types. To know if t

This device operates by utilizing the existing power supply from a standard 12V AC doorbell system. The circuit is designed to detect the ringing of the doorbell and store this event in a memory component, typically a capacitor, which retains the information even when the power is not present. The key components of the circuit include the doorbell coil leads, a rectifier to convert AC to DC, a capacitor for energy storage, and an indicator, such as an LED, to signal that the doorbell has been rung.

When the doorbell is activated, the AC voltage from the doorbell coil is applied to the circuit. The rectifier, usually a diode, converts this AC voltage into a pulsating DC voltage. This DC voltage charges the capacitor, which stores the charge as long as the doorbell is pressed. The charging time is short, allowing for immediate feedback, while the capacitor's discharge rate is low enough to maintain a memory of the event for an extended period, even up to 15 days, depending on the capacitor's specifications.

The LED indicator is connected in parallel with the capacitor and will light up when the capacitor is charged, indicating that the doorbell has been rung. This visual cue serves as a reminder for the user to check for missed visitors. The simplicity of the design allows for easy installation, requiring only connections to the doorbell's coil leads and minimal additional components.

Overall, this self-powered monitoring device provides a practical solution for individuals who may be away from home for extended periods, ensuring they are aware of any visitors who have rung their doorbell in their absence.This very simple and self-powered device was conceived to allow a person to monitor if someone has rung his home door-bell when he was out. As most door-bells use 12Vac supply, the circuit must be simply connected to the two door-bell-coil leads.

Though this device was primarily intended to be used when a person leaves the house for a few hours or a week-end, a number of tests has proven that a minimum of 15 days "memory" can be guaranteed, even using cheap capacitor types. To know if t 🔗 External reference