Lamp With Off Timer and Dimmer

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Intro: Lamp With Off Timer and Dimmer

This is one of the most basic 555 circuits. This circuit is part of this chips datasheet, complete with the math needed to design to specification, and is one of the reasons a 555 is referred to as a timer.

This is a monostable circuit, one of the most basic 555 circuits; it has two distinct states, one of them stable (having a steady voltage) and the other one unstable (having an unsteady or variable voltage). Normally, the circuit is in the stable condition. The circuit can be removed from the stable condition temporarily by an input pulse called a triggering signal. After a certain period of time, which can be adjusted or set by choosing specific component values

{t = 1.1*Rt*Ct}, the circuit returns to the stable state until another triggering signal is applied.

Eg: Rt= 10 kilo ohm, Ct=100 microFarads; therefore t= 1.1*10^3*100^-6 => t= 1.1S

In the schematics you'll notice two potentiometers; one of them increases/reduces the brightness of the LED's (Rpot1) and the other increase/decreases the period of time before the LED's turn off.

I also added a switch which allows me switch from normal mode to timer mode

The pushbutton starts the timer so when pressed the LED's will turn on for 1.1 seconds .

If you decide to add a potentiometer that varies the time then the formula becomes: t = 1.1*(Rt+Rpot)*Ct
Click the link to learn more about monostable circuits:

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