Retrofit a Incandescent Flood Light to LED




Introduction: Retrofit a Incandescent Flood Light to LED

I had installed in my house's porch an 500W incandescent flood light for soooo many years. But i thought that 500W worth the try to change it to something modern and energy conservative. In my searches around the internet something that is called led COB catched my eyes and i started to search about them. After a while and after reading some similar projects the idea formed inside my head and decided to proceed.

I feel comfortable tampering with the mains voltage which is 220V in my country but if you have never done any project using the mains voltage you should be extremely careful.

So let's get started!

Step 1: Buy (or Gather) the Parts.

I have found very cheap LED COB on ebay 50W for $1.67

COB (Chips on Board) , is a new technology of LED packaging for LED light engine. Multi LED chips are packaged together as one lighting module. When it light up, it looks like a lighting panel

This technology produces a lot of heat so the base of the COB is metallic to help heat dissipation. To dissipate heat we have to attach a heatsink. To help contact we have to use a highly heat conductive paste. I have chosen this one from ebay because it is cheap and suggested for LED heat dissipation. It costs around $1.20 for 30g. I have used about 5 grams for this project.

The old flood light that i have used (not the same with this picture) was rated 500W and the heatsink was from an old processor.

Step 2: Gather the Tools

    • Screwdriver (of course)
    • Metal brush
    • Electric drill and 2.5mm and 2mm drill bits
    • Four 2mm thick, 2cm long screws
    • Solder iron, paste and wire
    • Silicon gun
    • Rotary grinder
    • Gloves
    • Protective glasses

    Step 3: Dissasemble the Flood Light

    Remove the front glass loosening the screw on top and remove the lamp. If you want to reuse it we have to use a paper to hold it and do not touch it with your hands. Take out the aluminum reflective surface removing the screw at the bottom. After, loosen the screws to remove the base that was used to hold the old lamp.

    Test to see if the led COB sits firmly at the bottom of the housing. In my case the led COB was 1-2mm wider, so i grind it using the rotary grinder.

    Step 4: Positioning the Led COB

    I have cleaned the surface inside, using a metallic rotary brush and after that i placed the led COB inside the housing and marked the holes for drilling.

    I have used a 2.5mm thick drill bit for the flood light housing.

    At the exterior of the housing i wanted to place the heatsink. But there were metallic bumps and in order for heat to dissipate, a firm contact is needed. I used the rotary grinder to remove as many bumps as needed for the heat spreader to sit firmly on the exterior.

    Then i marked and drilled 2mm holes at the heatsink.

    Step 5: Soldering the Cables

    I have used the older cables that were inside the flood light. There were covered with some heat protective sleeves so i thought that this will help if the temperatures rises inside the flood light.
    I have used a lot solder paste. As you can see the connections aren't very good but i pull the hard and the kept in place. I am not sure why the solder could not cover the wires but i believe that this cables need different solder wire. Anyway i used the silicon gun to cover them in a next step.


    If you do this project you have to make sure that the cables touch ONLY the two areas designated as L and N and nothing else. The bottom of the led COB is metallic so you have to be extremely careful. Consider that you are going to connect it to the mains. Also make sure that this two cables are not touching the exterior of the flood light casing or touching together. This is the most significant part of the project. if you are not sure that you have done it correctly the don't do it. In every case you can use a multimeter, in the contact setting, to test the connections.

    Step 6: We Have a Thermal Contact

    I have put enough thermal conductive grease paste inside, at the bottom of the flood light and pressed the led COB firmly and put the 2mm four screws in place. I didn't have to screw them because the holes were 2.5mm.

    At the exterior i also put grease paste between the grinded surface and the heatsink and screwed the heatsink with the screws.

    I have made a sandwich with led COB on top, grease paste, flood light casing, grease paste and heatsink.

    Step 7: Final Steps and Thoughts

    In order to avoid electric contact i have used the silicon gun to cover the two electric connections.

    Make sure that there is no contact between the two cables and anything else except the led COB. You can use a multimeter in contact setting to test if you are not sure. The flood light is going to be connected to the mains so you have to make sure that you have done everything with no errors. A descent LED flood light costs less than 30€. Buy one and don't bother. There are thousand other projects using batteries.

    I have placed the aluminum reflective surface after cutting the interior according to the led COB's dimensions. I made sure that it couldn't touch the led COB in any case. Finally i closed everything.

    Final thoughts

    Does it worth it?
    It took me about 2,5 hours to complete the project. Most of the time was for the grinding process. The money that i have spent are less than 4€. The pleasure that gave me cannot be measured. I could probably buy a better led flood light for 30€ but turning the switch on and off would never give me the same pleasure.

    Post making - Measuring and fixing some deficiencies.
    After some comments from fellow intstructable makers, i have fixed and resoldered the connections cleaning them with solvent. Also i have measured the wattage consumption and i found out that it is only 28W instead of the 50W that the seller stated. It is the "cost" of buying cheap from ebay.

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      4 years ago

      Congrats for the article. Until now I have dis several of these adaptations with great results, even not using external heat dissipator. I suggest you to measure the Wattage of final assembly because, on my experience, the round cornered LED COBs hardly deliver more than 75% of stated WAtts, so I ever choose the rectangular shaped that commonly exceeds the advertises Watts. Well done !


      Reply 4 years ago

      You are right grasnall. I have tested both types of the led COB's and
      the supposed to be 50W is just 28W and the smaller 20W is 16W.

      Another thing is that when they are getting hot they become dimmer and the
      wattage consumption drops. So i am pretty certain that a heat dissipator
      should be installed.


      Reply 4 years ago

      Thanks for your commets,gkal. In fact, if the heat dissipation is not properly done, you can notice the Watts going down until certain level. I deeply believe that when this happens, there is a great risk of damage the leds, due to poor heat dissipation.Some time ago I needed a great heathsink for two 50W COB leds devices and as heathsinks needed were too much expensive I decided to use a motorcycle cylinder (please refer to attached picture). The results used to be very good.


      Reply 4 years ago

      What a great idea!


      4 years ago

      Take the cables off ,clean the ends with acetone or alchohol and heat separately and apply flux and solder . Don't try to connect until the solder is all over the ends . Then just touch them on the board with the iron and they will be good


      Reply 4 years ago

      Very good suggestion. Thank you.