Solar-powered flashing LED heart pendant PCB coil

for Mouser and MacroFAB Blink An LED competition

Similar projects worth following
Starting from
bobricius has 2076 orders / 91reviews
Ships from Slovakia
Whats it is make special MacroFab Design Contest: Blink an LED Sponsored by Mouser Electronics ???

- Most innovative and ultra best solar harvester,
- I am sure that it is new blink principle :D
- 0.4V startup ! very innovative design with onboard pcb coil transformer
- only 2 BPW 34 for generate power
- very easy replicable
- minimum components, all magic is hidden in PCB structure
- wearable, compact, this is new generation of self powered LED jewelry
- innovative
- effective
- reliable
- with good coating survive doomsday
- no direct sunlight required, work much better in shadow
- again, easy replicate 5 components only
- ideal kit for learn to solder
- no batteries, no waste
- environmental friendly, work foreeeeeeeeeewer

I designed and ordered new board with heart shape, unfortunately It is not possible receive it before contest end. I providing proof video based on my 1 inch joule thief. 

I am very sad that I can not show new board in action.


Design is based on joule thief, 2x BPW34 solar cells are used to charge storage capacitor, when voltage rise above startup voltage, joule thief make LED blink from storage capacitor, all is repeating.

Flasher is based on classic joule thief design usually based on toroid transformer, but in this case
is transformer etched on PCB, Joule thief usually works as continuous light device but thanks to to combination
low current source + storage capacitor and startup voltage hysteresis it blinking !!!!

I think It is world first one component led flasher


  • very simple Transistor + LED + Solar cells + capacitor
  • small, just 1 square inch
    ( for heart pendant little enhanced )
  • durable unbreakable solar cells
    ( BPW34 are plastic )
  • innovative design, all magic in PCB structure
  • very elective
  • wearable, new generation self powered led jewelry
    (can be coated transparent resin and survive doomsday ) 
  • harvesting power supply, can be used as module for powering another devices

Flashing is faster and much more powerfull but my camera can not catch all flashes,

I can take video in night for more proof..... ouch it is solar powered .. I am sorry ...


  • on schematic are 2 leds, because you can use SMD or TH led
  • Resistor is 0R, it is only for future tuning, but is not required
  • you can order testing prototype board here PCB coil joule thief
    (just connect capacitor an diodes,)


Heart PCB

Bill of materials with Mouser links to each component:



Prototype, working and tested board

brd - 351.16 kB - 09/09/2018 at 21:09


sch - 264.95 kB - 09/09/2018 at 21:09



Heard shaped, to carry all components

brd - 472.07 kB - 09/07/2018 at 21:54


sch - 264.32 kB - 09/07/2018 at 21:54


  • 2 × BPW34 Opto and Fiber Optic Semiconductors and ICs / Photodiodes
  • 1 × Capacitor 100uF or more
  • 1 × LED ... RED or GREEN, smd, TH ... your choice
  • 1 × MMBT2222ALT1G Discrete Semiconductors / Transistors, MOSFETs, FETs, IGBTs

  • 1
    Just assembly and enjoy

    It is ultra crazy simple, because all magic is in PCB structure, no coil wind, nothing .... just solder few components

View all instructions

Enjoy this project?



baicker.009 wrote 03/01/2024 at 04:34 point

why i can't flash the led, I measured that the solar panel provided 0.9v, is it too low ?

  Are you sure? yes | no

Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates