555 Timer, Variable Blinking Light

Introduction: 555 Timer, Variable Blinking Light

Thank's to the Instructables Build Night sponsored by http://www.jameco.com/, hosted at http://archreactor.org/, I bring you a 555 timer based project that blinks an LED at a rate that's affected by the intensity of the light in the room!

Things you need:
- breadboard
- 9V battery
- LED
- couple of resistors
- Photo-resistor, or LDR
- many jumper wires

Step 1: Connect All the Things!

Wire up the circuit on a breadboard.  There's some leeway in the resistor values.  Changing the 10K will change the blink speed, and the 3.3K you should change based on the LED you use.

Step 2: Move Around to Different Lighted Areas!

It should blink faster with more light!

Thins to do:
- add an inverter circuit so that it'll blink faster in darkness!
- try different LED's!  the big yellow one was in Jameco's grab bag, it has 6 LED's inside it, all 5V forward voltage which is why I took the resistor off.
- replace the LED with a buzzer!  place in your refrigerator to see if the light stays on when the door is closed!
- replace LED with a transistor and drive a big high power led!
- replace photo-resistor with a trim pot and set your own blink rate!

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    3 Discussions

    it's on the schematic, 10uf. for this project voltage isn't very important, but it should be an electrolytic type.

    You can increase or decrease sensitivity of LDR's Light sensing ability by adding a Variable Resistor/Potentiometer with LDR.
    Nice instructable though