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Power-on Reminder with LED Lamp Schematic Circuit Diagram

Frequently, equipment in workstations inadvertently stays powered on, which can lead to overheating and potential damage. To address this issue, here’s an additional device designed for workbench power supplies: the “Power-on Reminder with LED Lamp.” This device periodically alerts you to the powered-on status of connected devices by activating a buzzer for approximately 20 seconds, typically every hour. Additionally, it features a white LED that offers sufficient illumination to help you locate objects in the event of a main power failure.

Here’s a description of a simple “Power-on Reminder with LED Lamp” circuit along with a high-level schematic diagram. Please note that the specific component values may vary depending on your requirements and component availability.


  • Timer IC (e.g., NE555)
  • Buzzer
  • White LED
  • Transistor (e.g., NPN transistor like 2N3904)
  • Diode (e.g., 1N4148)
  • Resistors
  • Capacitors
  • Power supply (e.g., 9V battery or regulated power supply)

Power-on Reminder with LED Lamp Schematic Circuit Diagram


  1. NE555 Timer IC: This IC is configured in astable mode to generate a periodic pulse signal. Pin 4 (Reset) is connected to a capacitor-resistor network (R3 and a discharge resistor not shown) to periodically reset the timer, creating a repetitive time interval.
  2. R1: A resistor that sets the charging and discharging time constants for the NE555 timer.
  3. LEDs: Two LEDs are used in this circuit. The first LED (connected to Pin 3 of NE555) serves as a power indicator. It lights up when the circuit is powered on. The second LED is the white LED used for lighting and is controlled by the transistor.
  4. R2: A current-limiting resistor for the first LED (power indicator LED).
  5. R3: A resistor that, in conjunction with the discharge resistor (not shown), sets the time interval for the reminder buzzer.
  6. Buzzer: The reminder buzzer is connected to the output pin (Pin 3) of the NE555 timer. When the timer’s output goes high, the buzzer sounds for around 20 seconds, reminding you of the power-on status of your equipment.
  7. Transistor: The transistor is used to control the white LED. It is switched on and off by the timer’s output. When the timer’s output is high, the transistor conducts, allowing current to flow through the LED and illuminate it.
  8. Diode: The diode is used to protect the transistor from reverse voltage when the LED turns off.


  • When the circuit is powered on, the power indicator LED will light up.
  • The NE555 timer generates periodic pulses, and when the timer’s output goes high, the buzzer will sound, reminding you of the power-on status of your connected devices.
  • Simultaneously, the white LED will also illuminate to provide light in case of a power failure or when you need to locate objects.

The values of resistors (R1, R2, and R3), capacitors, and the specific part numbers for the timer IC, transistor, and diode will depend on your specific requirements and can be adjusted to achieve the desired timing intervals and LED brightness.


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