Introduction: High Current Flickering Pumpkin LED Driver
Use a LED Tea Light to Drive High Current LED's that is simple and easy to make.
Designing the circuit that produces a true real looking candle-flame effect is very difficult to accomplish. I wanted to make a simple and quick way to drive higher current LED's without all the hard work. I was looking at a LED Tea Light at Michael's Crafts Store and the realization came to me why don't I just connect the flickering LED Tea Light to a drive circuit that can handle the higher current loads to produce a high current LED Driver. The hard part of the circuit design was completed by the purchase of the LED Tea Light that cost a couple of dollars.
Step 1: Take Apart TheTea Light
To open the Tea Lights you cut with a knife 1/2" in from the bottom until you cut through the plastic so the top will come off. With the top off I soldered a wire to the (+) anode lead of the LED, this wire will drive the flickering effect of the high current driver. To locate the plus (+) side of the LED lead is to use a digital multi meter with the Tea Light turned on. I solder a wire to the negative side of the battery so we have a common circuit ground. In the picture the red wire is the (+) and the white wire is the negative battery terminal.
Michael's Crafts Store
GE (General Electric)
Flickering Tea Light LED
#362298 (One Tea Light)
#399217 (Six Tea Lights Value Pack)
Step 2: Circuit Design
The Tea Light produces the pseudo random flickering flame simulation by varying the voltage and current of the LED. The Tea Lights LED (+ Anode Lead) output drives the current of the BJT transistors making the output LED's flicker. To make the output LED's flicker you need to adjust the variable resistor R1 and R2 to a position as not to saturate the transistors output
but to make LED's flicker like the Tea Lights LED. A good starting point for R1 is 50K ohms and R2 is 20K ohms. The Output LED driver 2N3906 has a maximum IC of 200mA and that can be replaced with PN2907 for a maximum IC of 800mA.
The resistor Rx can be changed to control the current and voltage through the output LED's. I used 471 ohms for Rx to produce a maximum current of 25mA in each LED.
You can install many output driver sections together to produce more lumens of flickering light.
The circuit design makes a simulated candle flame effect to drive high current LED's, other high current loads, or HBLED, etc.
Step 3: High Current Flickering Pumpkin LED Driver in Action
See the video of the High Current Flickering Pumpkin LED Driver in action. Enjoy..................
Participated in the
DIY Halloween Contest
13 years ago on Step 2
Are you sure the Tea Light varies the voltage and current? I would sooner believe it creates a psuedo random PWM output to the LED. Meaning, it turns on the LED for random amounts of time. I can't see from the picture what exactly makes up the Tea Light circuit to say one way or the other though.
14 years ago on Step 2
I have been looking for something like this for a while... this seems to be a very nice approach to the flickering LED problem in that the lumen's or volume of light if you will can be adjusted... also no PIC and ATMEL devices need to be dealt with... wondering how a couple Cree-XR's would look... breadboard time... Thanks
Reply 13 years ago on Step 2
Neat circuit. The latest round of tea lights I bought, the 'flicker' was built right into the LED as opposed to being a separate circuit board as with the older designs. But this should work just about the same. I've used a very similar circuit and some 150mA 'straw hat' LEDs (ebay) to really light up some pumpkins. With the LEDs is you can light up plastic, foam, and all manner of otherwise 'flammable' pumpkins and decorations. Though I also have to have several real pumpkins with candles...just have to have the 'burning pumpkin' smell in the crisp fall air to really feel like Halloween! On a side note, experiment with the variable resistors, then swap out for cheap/small fixed resistors of the same value to really miniaturize the circuit.