The Center piece is a bamboo tube. The bottom of this pipe is a brass part. A autotransformer dial is the big washer. The LED array is from a Failed China Lamp and The Enclosure is a 10 CD Box. The Top Byzantine Structure is a Pepper Cap from Africa and a Furniture Knob.
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.
|From Hobby Hound – DIY Electronics|
Read Earlier Post – Perpandle Design
How It Works ?
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.