Smart Switch Timer

Ever have those days where you turn ON the switch and forget to turn it OFF after a while? This is the perfect device to do so.

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This project is developed to counter a major issue that prevails in households where appliances such as Geysers and water pumps have to be turned off after a while. Well there are third party devices that are added-onto the system to control the switching. This requires modification to the wiring and generally any changes in electrical system is not advisable as shorting of wires could damage the wiring and may cause fire. An alternative to that is to switch OFF the switch physically via an actuator. This way you keep yourself away from electrical risks and be safe!

This project has come a long way from what I had in mind earlier. This is the best version I can put out there and i'm very happy to present you my final build. This project at one point in time was a build that only could support at max 8 minutes of timer which illuminated LEDs based on the minutes, for example for 1 minute only a single LED glowed and for 2 minutes two LEDs glowed and so on upto 8 LEDs. This was fine but not good enough for times where you need to time for more than 8 minutes. The challenge was to use at max 8 pins of my arduino UNO to display higher numbers, which is when I got rid of the LEDs and got my hands on Hitachi's 1602 LCD display which takes around 6 digital pins and the rest are connected to the 5V and ground supply directly or indirectly via a potentiometer or resistor. This allows me to display whatever I want without worrying about how much I can display on it.

To control what is displayed on my screen I had decided on using a 4x4 keypad which requires 8 pins, but the challenging part again was the availability of pins. Therefore I decided to get rid of that and use a potentiometer that returns analog values back to the arduino based on the angle of the knob. This helped me control whats displayed on my screen with just a single input analog pin.. 

These were the challenges I faced and the way around it. 

WORKING OF THE BUILD: The build consists of two potentiometer, the one on the right to control the contrast of the LCD screen and the one on the left to adjust the timing of the switch. As we change the angle of the knob, the varying analog values is intercepted and a corresponding time is displayed on the screen, once we are done selecting the timing we require we have to press the button in the middle that initiates the countdown timer. The countdown timer is displayed on the screen in seconds after which the controller signals the servo to rotate in a specific direction and turns off the switch. In cases when the timer has to be discontinued, the button should be pressed again and the timer stops. The build supports upto 20 minutes of timer, which can also be increased as when we require.

Now that i have this, i can turn ON my water pump and set the timer on this and forget about it. This can be applied in various workplaces as well, for example in a workshop where soldering iron have to be turned off after use as not doing otherwise could prove fatal. One can set a timer for 15 Minutes when they turn ON the soldering iron and forget about turning it OFF.


video demonstrating the working.

MPEG-4 Video - 38.96 MB - 09/02/2021 at 20:00



Arduino Code.

ino - 16.77 kB - 08/31/2021 at 18:38



Base within which all the components are placed.

Standard Tesselated Geometry - 3.40 kB - 08/30/2021 at 16:57



Top lid that houses the LCD display which fits over the base.

Standard Tesselated Geometry - 18.44 kB - 08/30/2021 at 16:57


  • 1 × Arduino Uno Open source microcontroller board
  • 2 × 10K Potentiometer
  • 1 × LCD Display 1602A 8 bit Display
  • 1 × SG90 Servo Motor 1.3 kg/cm torque
  • 1 × PushButton

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Vijay wrote 09/11/2021 at 14:52 point

Love this project, sImple yet so useful! Brilliant work!

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