LED Panel Lamp




Well, yesterday I got attack of conscience and decide to make something local to improve world power shortage. I rebuild old halogen 12W lamp in my table lamp on modern LED light.

Step 1: Halogen 10W

This was reason which push me to work. I have electric power AC220V and it's transformed to plain AC12V which drive this lamp with 1A...o light and heat with 12 W. Very hot!

Step 2: Heat

You can see what heat of 12W do... plastic is melted. Well light color is warm about 3000K. Its not day light which we like much.

Step 3: Eternal Plexi

I took 5mm Plexiglas 120x80mm, drill holes for LED foots. Also I shall rectify AC to DC current.

Step 4: Serial

LED China. 11mm dia. 3.6V and 20mA. Each.And I have 12VDC output.What to do?
I shall connect LED serial !-so 4 leds shall easy hold 14.4V! In my case 12V divide with 4 is 3V. Less. OK.

Step 5: Mirror

I took alchoholic silver paint pen to paint bottom of each led. Do you know why?  To increase light in front direction. My moto: keep it simple.

Step 6: Assembled!

White wires are AC12V from transformer. AC is converted in DC with Graetz diodes, full wave, After that is 8 lines of 4 LEDs ...voila!

Step 7: Be Light!

Switch on! ...nothing burned...it works! Nothing is warm...even 4 Graetz-diodes (they are 1A) are cold.
Instead 2W I have output 12VX15mAX8=cca 1,5W... or so..

Step 8: And Light Is On!

I put on back(glued) 6mm sponge. (roll sponge for laying on pool...). YOU can put a tape. Or card paper. Or something else --- what you like. Just for better look and some protection. And
of course: WARNING. Do this on own risk. Not mine.



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    21 Discussions


    4 years ago on Introduction

    I'm new with this so I could use some help, are the LED's are connected in parallel or series? This will work if I use a ordinary resistor and power it up using as 12v battery? thanks..

    1 reply

    3 years ago

    Nice, I like it!


    5 years ago

    very high quality work! I really love the trick of using silver paint to add reflectivity. I've made dozens of such arrays (36led each ) for garden lights, however they're on blank pcb. the acrylic is adding a new dimension to the looks. very fancy!


    8 years ago on Step 8

    Very nice project , Its what exactily i'd thinking about , But u said u'd connect ur LEDs in series and u used 16 LEDs that mean u need 16x3=48 v , But ur power supply gives u only 12 V , Would u explain that for me cose i wanna convert my desktop lamp to the same , Thx.

    4 replies

    Dear, 1. I like to have your full name or Email.. 2. Each LED have nominal Voltage 3--3.6V Each LED is rated/calculated on 20mA (now we have also a bigger/stronger LEDs)
    3. Divide 12V (13V) with 3,6V you get  number 3

    4. 3,6 V X 3 =10,8  V
        3.6 V X 4 =14,4 V
    5. You can securely take 4 LEDs in series.
         Each line of 4 LEDs give you  20mA X 14.4 V = 0,028 W  of needed/used power .
    6. Desktop lamps are usually halogen lamp about 10-20W or more, so transformer is  already overpowered ...



    Reply 8 years ago on Introduction

    there is a lot of amps coming out the secondary side of the transformer.. because of that you can use an LED with 4/10 of a volt because it gets a lot of amps, or milliamps.


    Reply 8 years ago on Step 8

    Calculation is correct!
    I have 4 LED in series... it means 4 x 3 V = 12V total.
    Therefore I have 8 lines at 4 LEDs...paralel...
    You can put limen at 4 LEDS how much you want


    7 years ago on Step 8

    If I connect the half (4 lines X 4 LED's) to use the upper half of AC and the rest 4 X 4 reversed so they use the low transition of the 12v AC I think I can eliminate the use of the bridge diodes .I am wrong ?


    8 years ago on Step 8

    This is a nice way of constructing a desk lamp. There is only one small problem with the assumed voltages. If you rectify 12Vac with a Graetz you will get some 16Volts DC on the output. Therefor it would be better in my opinion to have an array of 3x5 LED's. In your lamp right now the LED's are drawing more current than what they are designed for and therefor lifespan will be much shorter. You can use this link to search for the best possible array. Please note there is a single- and a multi LED version http://led.linear1.org/led.wiz Sincerely, Ton

    1 reply

    Reply 8 years ago on Step 8

    This is not right, The peak voltage is ca. 17Volts, but this is the peak, and what counts is the Vrms and this stays at 12V. if you want to get 17VDC you have to add a Cap of a few hundred µF. This also reduces flicker to nearly zero. wtg hubert


    9 years ago on Step 5

    'Alchoholic' not alcohol based...lol ok ok good tip on to the next step....

     What if you lined the Plexiglas with a reflective material, say aluminum foil, silver leaf, or something of that nature (like how you covered the back of the LED with silver paint). 

    Or instead of a flat plexiglass surface, make something with a curve, similar to how a headlight works in your car.  It takes one bulb, and because of the concave reflective surface, it projects the light with stronger intensity.

    RadBearDoctor What

    Reply 9 years ago on Introduction

    A buddy of mine used to form plexi by putting it in a tray of sand and heating it in the oven. You might be able to curve the plexi by heating it this way and then laying it over a round form like a pop can.

    I've used metal duct repair tape as a reflector in several projects and it worked well.

    @RadBear... plexi forming is not so difficult. But, as I mentioned - purpose determine final form.  Yes  you shall collect more light in a spot. The very best is to find on car flee market defect car lights and use a part for such construction...  

    Idea is OK. Mirror like surface - parabolic helps a lot. Police flash lights. But, remember that each LED allready have a lens on front - built in. Narrow beam light is for exact purpose i.e. light with stronger intensity.Wide light is better for general purpose and eyes. Soft light.
    ONLY solution that you put so much LED s to reach power consumption of 80 % of halogen. In my case I have to add 20 strip of 4 LED s, to get similar output and quantity of light.