- Labs project
Power saving led light for children [140012-I]
October 11, 2013
Most led lights for children run on batteries. They only have an on/off switch, a resistor and one or more leds. This means that the led light will run for hours without the need and the battery power decreases rapidly. This project describes an small and easy to build modification so the battery power will be extended for many hours. My youngest child wants the led light to be on while he goes to sleep. After 10 minutes he is sleeping and the light does not need to be lit on anymore. I used an attiny85 to for timing and control. So, what did I do? The ATtiny85 is powered by the battery. It uses the watchdog timer and sleeps for most of the time. Once in a while it checks what to do, takes an action if needed and goes to sleep again. An additional pushbutton is used to program the timer and to turn the led light lits on or off. How to use? If the switch is powered on ( you don't have to turn off the led light anymore, but ok ) the led light will blink the number of the timer setting. First time use it will be 12 times. To turn on the led light, press the button once. It will lit on slowly. To turn off the led light, press the button once. It will lit off very slowly. To programm the timer, press the button for 10 seconds until it flashes one time (meaning timer setting set to 1). Every time you press the button again within 2 seconds after the last button press it will blink and increase the timer value. The maximum value is 12. If the button is not pressed for 2 seconds, it will blink the amount of presses (timer value) and save the value in the internal EEprom. The timer vallue is as follows: 1 : 1 minute 2 : 2 minutes 3 : 3 minutes 4 : 4 minutes 5 : 5 minutes 6 : 10 minutes 7 : 15 minutes 8 : 20 minutes 9 : 25 minutes 10 : 30 minutes 11 : 45 minutes 12 : 60 minutes Depending on the timer value, the led will lit off very slowly after the mount of programmed minutes. components: ATtiny85 small pushbutton N-channel FET The firmware is programmed with arduino software. To make modification to the firmware, you will need t install the latest avrgcc with some modifications to the avrgcc config file. There seems to be a bug in the compiler 2008. arduino code, pictures and schematic will be posted in the near future.
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