Tips or Help in Designing LED Light Bulb for Ambient Lighting Conditions

Discussion in 'The Projects Forum' started by Ballerinda, Jun 17, 2010.

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  1. Ballerinda

    Thread Starter New Member

    Jun 17, 2010
    3
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    I am trying to experiment and gain an understanding of lighting. Attached is a document with my schematic, most likely off. I think my diode is not places right in the circuit. If someone drew an update it would be grealty appreciated.

    I have 10 1W LEDs with a foraward voltage of 3.3 to 3.6V and forward current of 350mA. they are also 80lm a piece. I want to create an energy effieicnt bulb using all 10 LEDs, giving me 350mA, 33 to 36 forawrd voltage, and 800 lumens output.

    Problems I faced are regulating the voltage in and controlling it. I figured a zener diode voltage regulator would work. Its for a light bulb so I couldn't place in a transformer and save cost. I added a fuse to protect teh LEDs from current, then a capacitor C1 to store some charge, then a full wave bridge rectifier to go from AC to DC voltage becaus ethe LEDs run on DC. If not theyd keep blinking on and off. Then I put a capacitor C2 to smooth the signal from the rectifier, a resistor Rs to control the bleeding from teh capacitor when the bulb discharges. Then i used a zener with that resistor to control the voltage coming into the LED part of teh bulb.

    There might be a reistor needed, liek a load resistor after the zener, and before the LEDs, and also I think the Rs resistor should be in series to act almost like a shunt resistor.

    If you have any tips
    1. Improving the circuit or fixing it
    2. Controlling the 120 +/- 10V coming from the wall and current
    3. Making it effieicnt comparable to 100W or 60W incandescent
    or any feedback at all,

    please let me know. Its a small project, and I am looking to cut the cost back to build it as I spent a lot on materials so far. I was also wondering if the bulb has 10W from the LEDs, does that make it a 10W bulb? Im just looking for help and clarity.

    -Thank you so much for any help you can aide me with.
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    Leds are current controlled devices and not voltage controlled.
    You will need to regulate the current with a current source.

    We urge you to use a transformer to make a safe circuit.

    Bertus
     
  3. Ballerinda

    Thread Starter New Member

    Jun 17, 2010
    3
    1
    I could always throw a resistor in series with the 1st capacitor to controll the current.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    282
    Stuff like this with a UL seal on it is fine, but homemade is not a good way to go. Your circuit is not at all safe, unless all components are in a potted box. Any failure in the capacitor, and it's all at line potential.

    We would recommend that you buy an approved LED replacement bulb - or plan to use a step down transformer.
     
  5. dsp_redux

    Active Member

    Apr 11, 2009
    182
    5
    Honestly, you should use a transformer to protect yourself from the main's power. Why don't you use two parallel branch of 5 series LED instead?
     
  6. Ballerinda

    Thread Starter New Member

    Jun 17, 2010
    3
    1
    My problem is that this is for a project.

    Why would it be better to arrange the LEDs in parallel. Wouldn't they conduct more heat.

    And I need to fit my design into a standard light bulb socket from a ceiling, so I need to rectify and drop the voltage. I was trying to make a transformerless power supply, as per http://www.aaroncake.net/circuits/supply5.asp.

    I figured that would save me time and money. A transformer would become bulky and heavy. If there are smaller versions or ideas to overcome this, what would you recommend?

    Also I was wondering if my resistor should be placed horizontally or parallel as is. Also should I add a resistor by the first capacitor, and another resistor after the zener diode to act as a load resistor?
     
    LupusDacicus likes this.
  7. Wendy

    Moderator

    Mar 24, 2008
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    This is one of the circuits we strongly discourage here at AAC, since it can not be made safe, especially by beginners. You will blow every diode in that circuit, since you don't have LEDs back to back (one facing each way). LEDs are diodes, but they were never meant to handle the back voltage you will be putting them through.

    I've written a guide for beginners on LEDs, including how to vary their brightness using PWM.

    LEDs, 555s, Flashers, and Light Chasers
     
    Last edited: Jun 17, 2010
  8. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    There is no safety built into that circuit at all. With no isolation, the circuit is a lethal shock hazard.

    There seems to be no point in continuing this thread.
     
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