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Saving energy is important issue for many people and countries. We want to keep our environmental footprint as small as possible and reduce unnecessary energy consumption. We need to save energy and reduce waste of energy when no-one is using it.

Home lights are often switched on when people at home do not stay at room. We want to save energy and turn light off when person is not in room or use external lights wherever it is possible.

Developing a simple solution for intelligent light control we actually do a first steps of introducing a smart house concept and home automation which can be later expanded for more sophisticated system.


Design Task

When motion is detected by a passive infrared (PIR) sensor, light will stay on for at least a period of time, on average 2 minutes, so that it can provide illumination for this time if the person that triggered the sensor stays in the area. Then, after this period of time has elapsed, it will shut off. If the person continues moving in the vicinity of the motion sensor, it will then be triggered again and stay on for 2 minutes again. This cycle will continue as long as needed. Control panel will record the saved energy and presents it on the LCD screen. User can also adjust light intensity either manually or automatically from the control panel. Automatic intensity control uses light intensity sensor to detect ambient light and necessary illumination.


Design Process


  1. Find similar solution and study theory or working principles.

  2. Choose PIR and light sensors

  3. Choose controller and user interface board

  4. Decide, how to connect light or how to simulate it

  5. Make electrical schematic

  6. Make wiring to connect sensors and controller board according to schematic

  7. Connect appropriate relay and/or LED lights

  8. Check again if all devices are connected right

  9. Connect programmer or USB cable to program the controller



  1. Install a programming environment which is suitable for chosen controller

  2. Check if connection is established between PC and controller

  3. Draw a program algorithm flow chart

  4. Implement a program according to the algorithm

  5. Debug and eliminate programming and logic errors

  6. Check if program and entire solution meets requirements



  1. Make documentations and user manuals



This simple system demonstrates how to develop a smart system where lights are controlled by environmental conditions like ambient light intensity and people in the room. Based on this experience there is easy to expand the system with more sensors and lights to control whole building or make software algorithms more intelligent and take into account also date, holidays and other parameters.

Expected Learning Outcomes

  • To find out how microcontroller based systems work
  • To understand the principle of how a passive infrared and light intensity sensor works
  • To build a simple smart home systems
  • Learn basic programming and flow logic
  • To investigate some simple electronics systems and facts



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