Led Strip Bulb Prototype




Hello everybody!

Here I am for presenting my first instructable...

I am a boy from Tuscany, so... Sorry for my english!

Step 1: Materials

Main items that we need:

  • a connection of an old bulb lamp
  • a transformer
  • 2 diodes
  • 2 capacitors
  • 2 5x20 fuses (2 A)
  • 1 LM7824
  • 1 thin aluminium sheet

Step 2: Electric Circuit

These simple circuit is composed from three parts.

The first part is the transformer. I have a 230/12 V transformer but I have a 24 V led strip, so we need the second part of the circuit.

The second section is a voltage multiplier, that is very similar to a rectifier bridge, but composed by 2 diodes and 2 capacitors, instead of 4 diodes. With this bridge we raise the voltage about 30 - 35 Vcc with a ripple.

The third section is the integrated circuit LM7824, that helps us to have 24 Vcc, not still pure, but perfect to give power to a led strip. To have a flawless 24 Vcc we need 2 or 3 capacitor before and after the LM7824 to filter and level the voltage but I haven't enough space.

Step 3: The Led Strip

The strip absorbs 0,046 A each 10 cm, we use 200 cm of strip, so the current will be 0,92 A. The maximun current that gives the LM7824 is 1 A, I know that this is an extreme situation, but this is only a prototype, an also we put an heatsink on it.

Step 4: The First Part

Let's make the first section, solderind the bulb connection, the 2 A fuse an the primary coil of the transformer. The transftormer enters perfectly in the plastic "bowl" of the bulb lamp, than we can try the circuit voltage.

Step 5: The Second and the Third Parts

We need a round shaped board to mount the circuit on it, put the heat-sink with a little bit of silicon conductive paste on the LM7824, make a nock with the dremel for the wires passage.

Finally we can try the voltage and the strip worrking.

Step 6: The Strip Holder

Working on the aluminium sheet we must shape it into a cylinder, that enters in the place where there was the glass ball. I hope that the pictures explain better than me the process. The width of the sheet is determined by the length of the strip.

Step 7: The Last Step...

Mounting the strip on the cylinder with some cable tie and connect it to the circuit.

Finally arrives the test... OK!

In the last photo, with the horizontal bands that you caught only with the camera, you can see that the output voltage is not perfect but a bit fluctuating, as previously described...

Thanks for reading my instructable! Sorry for my imperfect english!


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    10 Discussions


    2 years ago

    this is cool and really well made but this is actually a type of light that is sold its called a corn light!


    2 years ago

    Cheap bulbs use a capacitor to reduce voltage (z=1/C*omega where omega is 2*pi*f) and a bridge rectifier, and that works provided there's no need for dimming. You can even connect such bulbs to a trailing edge dimmer, that works (not that fine but...)


    Reply 2 years ago

    A led strip bulb prototype with an heatsink prototype... :)


    2 years ago

    Very cool, next step is to make a led disco bulb.


    2 years ago

    Your English was better than a lot of people who speak it as a native, so no need to apologise for it.

    Nice instructable. I imagine with the transformer it wouldn't be real cheap/easy to do this with a lot of bulbs. I've read about capacitor circuits being used to control led current with ac power, and I've noticed it's used in a fair few led light bulbs I've bought for the house. Have you any experience with these circuits? I've just noticed a lot of these have stopped working, want sure if it was the circuit or because they are cheap Chinese bulbs

    1 reply

    Reply 2 years ago

    Thank you!

    The transformer and all the items are old recycled components, I haven't spent a lot, the problem can arrive constructing a bigger number of bulbs.

    Led bulbs that you are talking about, I think that the cheapest has the voltage reduction with something in series with the voltage regulator that causes a primary voltage drop. More expensives led bulbs I think have a PWM voltage regulator.


    I serisously need to start building my own light fixtures so that I can customize the shape and size of the lighting in my bathroom.