A Tree Of LEDs That Blows Out Like A Candle

The beautiful workmanship in [Andrew]’s LED tree is gorgeous all on its own, but of course there’s more going on than meets the eye. This  LED tree can be blown out like a candle and it even playfully challenges a user to blow out all the lights at once in a single breath.

Some of you may remember the fascinating example of an LED you can blow out like a candle which had the trick of using the LED itself as a sensor. Like any diode, the voltage drop across the LED changes very slightly based on temperature. By minimizing thermal mass with surface-mount LEDs and whisker-thin wires, it was possible to detect when the LED was being blown on.

The LED tree shown here uses the same basic principle, but with a few important changes. The electronics have been redesigned and improved, and the Arduino used in the original proof of concept is ditched for stacked custom PCBs. Each board has a diameter under 100 mm in order to take advantage of the fab house’s lower cost for small boards. [Andrew] says that while the boards required a lot of time-consuming hand soldering and assembly, the payoff was that five boards rang in at barely five dollars (plus shipping) and that’s hard to beat.

Watch the tree in action in the brief video embedded below.

14 thoughts on “A Tree Of LEDs That Blows Out Like A Candle

  1. Fascinating LED sculpture. TLDR; Except for a JK Flip Flop, it’s a analog design (no uC). And of course it has an LM555. Component count is high, but that’s the price of admission when you want to make something in an unusual and interesting way.

      1. It’s possibly a trade-off between sensitivity of the circuit to noise, versus the temperature-induced change in voltage drop that you’re looking for as the signal to turn off.

        Also, it’s more of a challenge. I’m sure the only professions that would be capable of blowing those candles out easily would be politicians and lawyers, as few others are long-winded enough. :-)

  2. On the picture (*) you can see some small heatsinks put on top of some components. The heatsinks are easy to get and i do have some, but i wonder what kind of glue(?) he used. Does anybody has a cheap stuff to recommend? The last time i looked heat-conductive-glue was expensive and only usable for several weeks or month once opened. Is this (still) true?

    * https://bytechlab.com/content/uploads/2019/02/LED-tree-finished-top-view.jpg

    1. Guessing they are the typical super cheap ‘raspberry pi heat sink kit’ or similar. They come with some double sided tape. At this kind of level you can just use sticky tape to hold them on. Since you’re not going to be cooling a PC processor with these tiny things, you can get away without proper heat-sink compound

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