Halloween is coming and [Paulo] decided to make some flickering jack-o-lanterns by hijacking the flickering circuit of a cheap LED tea light to drive a much more powerful light!
He has tons of old 12V incandescent bulbs collecting dust, so he decided to make use of them for some holiday fun. He wondered if he could steal the circuit from the flickering LED tea lights and use them to drive the incandescents. Upon taking the LED tea candle apart, he discovered there was no circuit, as it was in fact embedded in the LED itself! Not to worry though, he simply integrated the flickering LED into his circuit! Coupling a capacitor with the LED, he used a transistor amplifier to take the signal, and then finally boosted it using a MOSFET to drive the light bulbs. He then powered the entire thing using an old laptop power brick. Nice one [Paulo]!
Do you have any cool Halloween hacks? Don’t forget to send them in to the tip line! For other pumpkin fun, check out last year’s Pumpkin Tetris!
19 thoughts on “Flickering Pumpkin Lanterns”
Not all tea light LEDs have embedded flickering. The ones i have and use have a chip on the side. I like swapping the warm LEDs for a cold blue ones for that creepy magical feel.
You should be able to put ordinary LEDs in series with a flickering one. As long as the voltage is high enough, then they’ll all flicker at once.
Gawd I hate this time of the year – we won’t get anything sensible out of you yanks until after Christmas! sigh…
You need to learn to man up and worship capitalistic orgies in the name of dubious religious histories and co-opted paganism like a right-thinking person.
LOL – that reply will give me some consolation over the festive season – well done! :-)
Can’t deny the overflow of that halloween stuff also annoys me, and it’s not just hacks, it’s also TV and such. But yeah, guess we’ll have to suffer through it.
how much of the schematic is your add on and what part is reverse engineered from the led tea light?
The circuit “from” the tea light IS the tea light! You connect them to a battery and they flicker away, convincingly. It’s an ordinary-looking LED with some sort of flickering circuit built into the LED housing, possibly on or near the chip that emits the light. Perhaps a look with a magnifying glass would prove illuminating. A-ho-ho!
As the tea LED naturally flickers on and off, it’s current draw will vary accordingly. The AC component of this drives the transistor through the capacitor, so the lamps will flicker on and off in time with the LED.
Can anyone tell me what the 100k is for, can work out the rest.
100k resistor is a pull-down resistor. It is to make sure the MOSFET turns off quickly when no signal is present.
When is there ever no signal present ?
It looks like its part of a voltage divider with the 1K, futzing with the trigger voltage of the mosfet?
I would have used a photoresistor I imagine.
The problem I’ve always had with the fake candles is that they’re limited by the poor frequency range of the LED. They don’t have the warmth of a real candle flame. I imagine that there are some better engineered versions than the dollar store version I’ve seen though.
The pound shop near me has some gizmo or other with a full-colour randomly changing RGB LED. I haven’t bought one but I’d guess it’s the same 2-pin thing, I know you can buy them as components.
They also do those tiny USB Bluetooth dongles. Not bad for a pound. Even Ebay does them for more than that.
I did take apart a USB air freshener though. A small PCB that itself made up the USB plug, leading back to 2 little SMD resistors. I forget the value but they added up to 500mA at 5V. You’re supposed to pour a little bottle of some bizarre smelling toxic waste on to evaporate it.
Which is ironically a job performed in the past by those vapourisers powered by… a tea candle! Awesome!
I would guess tapping into the RGB flashers would result in an output netting the RGB combined output, ie like putting through a B&W filter
Since it’s only 2-pin you’re probably right. When one goes dark, if the others light up, then overall the current draw will be pretty constant.
The LEDs you mention do have inter-color fades so there would be slight dimming there… You are usually picking up the PWM signals when using the method
Hi, I actually did this last year but used a red 1W LED, flickering LED and a 2N3053 with the flicker LED connected between Vcc and base and the LED on the collector.
Was still working three days later but got dimmer as the batteries faded.
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