High Power LED Blinking Circuit

Evil Mad Scientist Labs brings us this easy to make LED blinking circuit. The idea is to put a LED in series with a small blinking incandescent bulb from a string of Christmas lights. The bulb has an internal bimetallic strip that bends out of shape when it heats up, cutting the circuit. when it cools enough, it returns to its original shape and closes the circuit again, making the bulb and the LED turn on. Both lights have short period of sustained light when they are initially powered up since the bimetallic strip is still warming up.

The project uses a 5W blue LED, the aforementioned bulb, and a 6V battery pack loaded with 3 AAA batteries. The battery pack and the lights are all attached to a small section of perforated board. Duplicating this project should be easy and provide a very bright LED, but to make a 5W LED shine its brightest, a larger bulb and a heatsink will be necessary.

7 thoughts on “High Power LED Blinking Circuit

  1. The light is clever, and saves you the need for a resister, but unfortunately your “immortal” diode circuit is now mortal. :p
    (And of course the auxiliary light might be annoying… if it suited your purpose, you wouldn’t need the LED!)

    Surely someone makes a reusable fuse that operates on the same principle as the light?

  2. Tiny hack of dubious utility, but ok… Why use a 5W LED though? I used to duty-cycle regular old LEDs and they’d take several Amperes at low duty cycles. Imagine what a heat-sinked 5W (back-of-napkin guess: 4×1.5 = 6V, 5/6 = 830mA) LED could do when I was putting 2A through a 20mA LED with no heat sink!

  3. I think this exact same thing is found in the indicator circuit in a cars indicators, i think its located on hte fuse box, it heats up and cools down on the exact same principal as the christmas light except no extra light. I have no idea how youd interface with the one out of a car though, i imagine it would require 12v to operate it.

  4. I think the hackaday text should say 4 AAA batteries, not 3. Although the LED may work fine at 4.5V also.
    The light bulb will act as a current limit resistor. If the value is appropriate then he should have no issue of burning the LED out.

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