Perpetual Candle – Emergency Light 1W using LEDs, Solar panel can be also integrated with a single diode at input of LM317T. If your Solar Panel Voltage is low then use a DC/DC Converter or Joule Thief.
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|From Schematics of delabs|
View Schematic right here (may not work for browsers still in olden age). Click link below to see the schematic magicallly appear. Drag Drop Image with mouse for scrolling in all directions.
Source in Cadsoft Eagle format – candle.zip
Did it work ?
Here it is, not a nice photo, but this is all could do now. The Perpetual Candle is built into a Joy Stick that i never used. it is built around parts i have in my old inventory, LED’s are of this millennia.
|From Hobby Hound|
The Center piece is a bamboo tube. The bottom of this pipe is a brass part. A autotransformer dial is the big washer. The LEDs on both sides of a PCB in a Translucent Plastic Measurement Cup which comes with Vitamin Tonics.
This is a easy to build LED lamp circuit for Learning and building skills. This is the first draft schematic V 1.0. It will need improvements for Higher Power Lighting.
I will give a short summary, The LM317 here configured for around 6.4V DC. The Q3 BC547 limits the current, you can select R3 to suit, make it 1/2W. The Ni-Cd battery pack 1.2 * 4 will not get Over-Current or Over-Voltage due to this circuit.
The IRF540 Mosfet or any other equivalent you have around, along with Q2 BC547 forms a current source for the parallel 12 LED array. Ultra-bright White LED at 20mA each or use a 1W ready LED Chip. R4/R6 can be selected for the Max LED current. The voltage of LED is around 3.1 and 20mA * 12 = 240mA is the max current. You can Tweak the design for even 5A or more but then you will need a DC/DC High frequency converter in place of LM317. The Current source also needs to switch to improve efficiency. A PWM on the mosfet gives brightness control. The entire solution (switching) can be found in many chips with semiconductor vendors today.
Also use Heatsinks for both devices, may not be required, test is out.
Most of the parts in this are more than a decade old. The Brass part may cover even a century. The age of the bamboo tube can only be established after carbon dating. So olden it is, but the design and white leds are more new, this millennium to be exact!
Can i Build it ?
Yes, as long as it is for your own use. Even small quantities can be fabricated and sold at a moderate profit around locally. For manufacture in large numbers, you are morally bound to send me $ 1 for every 100 Nos sold.