I had purchased some cheap LED China bulbs but the LED's keep burning up. In an effort to improve them I opened some up and did some measurements.
With a 220/240 AC input and after some resistors, capacitors and a AC/DC converter the output to the LED's is 140v DC. If you divide this by the 36 LED's we get close to 3.9v per LED!
These are 5730 SMD's, this is why they burn out so fast. If I add more LED's say 49 LED's this bring down the voltage across the LED's to 2.8v and would extend the life of the LED's.
If I then add a heat sink it would keep the LED's cooler.
With this information I would then build a better more efficient and more durable lamp for my box room.
Step 1: Materials
One or more new or broken China LED bulbs.
One broken cover of an old fluorescent lamp.
Two aluminium strips.
a couple of threaded screws and nuts.
some cables and glue.
Step 2: Getting the Parts Ready
First find an old fluorescent lamp cover and cut a piece of about 20cm. I also removed one of the sides as this lamp was to be used in a box room but you could leave it and the end covers on for extra protection.
With little effort pop the top off the China bulb and desolder the LED strips and Bulb inner's but make sure to record the cable positions for later.
We now need two strips of aluminium to disperse the heat and support the LED's. I used two 14cm x 2cm strips and drilled some holes on the ends.
Step 3: Building the Inners
Drill some holes on the cover for both fixing it to the wall and for the aluminium strips
Clip the little locators at the end of the LED strips and stick them to aluminium strips with the heat-sink paste/glue making sure + goes to - to + and so on(I used some of the burnt ones by soldering a wire across the burned LED's making them a total of 49 LED's)
solder the strips together and add a little wire at the end to link to the next row.
Place inside the cover with a nut in between as a spacer to allow cooling space.
Step 4: Supply
Take the cover off the ceiling rose and pass it thru the lamp wire.
Locate the 140v DC connections on the bulb board and solder the wires from the lamp to them.
Stick the board onto the inside of the ceiling rose (glue gun) and connect the two AC cables to the supply.
Try it out and enjoy.