Last Halloween was looking for some alternatives to real candles to illuminate some Jack O'Lantern pumpkins had on the front porch of my house. I tried some of the inexpensive LED candles that were available at some of the local retail stores, but they worked horribly - they were not very bright and the flicker algorithm wasn't even random and looked completely fake. So to remedy this, I decided to design my own LED candle.
The first iteration was to design an LED candle that approximated a candle flame. I called this design the Digital Candle 1.0 and a demonstration video of this is seen here:
Note: The video below is the low power version of this circuit.
The Digital Candle 1.0 uses four (4) 1206 based amber LEDs is in a dark room very closely approximates a single candle. Its actually relatively bright in a dark room and great for that extra ambience - especially when camping or sitting around with your significant other for a nice romantic evening.
But in the end - i wanted more. So i decided to create a high power variant of the original Digital Candle 1.0. Hence, the new name - the Digital Flame 1.0. This kit was similar in design - used the same microcontroller IC and code - but utilized high power LEDs. I also decided to add a light detection circuit.
The light detection circuit can utilize either an onboard (provided) photo resistor, or an external photo resistor which detects the level of ambient light. When ambient light level falls below a preset level, than the device will turn ON. The level at which the device will turn ON can be custom set by the end user using an onboard potentiometer. The light detection circuit can also be disabled completely and the unit operated solely with the onboard switch.
The light detection circuit was primarily added with Jack O'Lantern illumination in mind. An external photo resistor can be used and attached through a small hole in the outside of the pumpkin, so that when its dark out, the digital candle will begin to operate without the user having to remember to turn a switch on or off.
This design utilizes four (4) high power PLCC-4 based LEDs and operates from two (2) AAA batteries which attach via battery clips on the rear side of the PCB board. Both an onboard potentiometer for light detection circuit adjustment and toggle switch are provided on the topside of the board for user control.
Step 1: Features
- Operationg Voltage Range - ~2.5-5.0V
- ON/OFF Switch
- Light Detecting Photocell Circuit (Unit will turn on automatically when it becomes dark out)
- Provisions for externally connecting a photocell sensor (onboard connector pads)
- Operates from two (2) AAA batteries
- Four (4) amber high power PLCC-4 LEDs
- Advanced randomization routines simulate burning candle flame using onboard microcontroller
- Onboard FLASH programming connections provided so you can experiment with your own microcontroller code