Perpetual Candle – White LED Lamp on Ni-Cd

Advertise in delabs

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.

One Single High Current LED may work well. 12 Matched LEDs also can be used. In LED Array some are dim, put min. resistor (3.9 ohm) for all 12 for current sharing. The resistor addition will impar the ability of Candle to work at lower battery voltages. Also resistor is less green, It wastes power, so use PWM and Single Die high current LED. Ni-Cd system may last over 5 Years if Candle is allways on Mains. Sealed Lead Acid system may go upto 2-3 years life but will have more punch. A SuperCap system may last more than 12 Years, i feel.

Source in Cadsoft Eagle format – candle.zip

More delabs Schematic Diagrams

  • Function Generator using ICL8038Function Generator using ICL8038
    ICL8038 and XR-2206 can help you build a Function Generator or Wavform Generator. It is needed along with the Oscilloscope and Power Supply on the [...]
  • Two Stage Sequential TimerTwo Stage Sequential Timer
    This is an example of a cascaded or sequential timer, here two CD4541 are forming a two stage timer. You can add more in a [...]
  • Digital 5V Power Supply using L296Digital 5V Power Supply using L296
    This circuit is derived from an application note of L296, It is a Power Switching Regulator from ST. The advantage of using a switching regulator [...]
  • Sample and Hold with Standby CD4053Sample and Hold with Standby CD4053
    A, B, and C are the Digital Control for x, y and z input and output pairs.The voltage at Vinx is stored in C1 when [...]
  • Interface ICL7135 Voltmeter to PCInterface ICL7135 Voltmeter to PC
    A PC based Analog Voltmeter. The Printer Port or Parallel Port Interface is used to acquire high resolution analog data using ICL7135. This is a [...]
  • Pulse width modulation using 555Pulse width modulation using 555
    IC1 astable gives a fixed square wave at pin 3, C1 and R1 derive uS trigger pulses from IC1 and this will trigger IC2 monostable [...]
  • Audio Visual User Interface with AckAudio Visual User Interface with Ack
    This circuit is an User Interface part of a Security Alertness Monitor that i designed decades ago. The circuits are here – Digital Circuits – Part 1 The RAM [...]
  • Connection Diagram of AC Control SSRConnection Diagram of AC Control SSR
    SSR or Solid State Relay or Electronic Relay Connection Method. This is a Thyristor Based Normally Open 230V Switch that can be turned on / [...]
About delabs 152 Articles
Product Design - Industrial Automation and Instrumentation. -

Be the first to comment

Leave a Reply