Introduction: Make G25 FAIRY Light BULBs for Halloween

Picture of Make G25 FAIRY Light BULBs for Halloween

For Halloween, given you use Orange and Purple or Violet Leds 'Fairy-lights' (aka Firefly) strings, they make for perfect subdued holiday lighting.

These 'FairyBulbs' put magic where and when you place them.

I had been waiting for someone to make these ... they didn't ... so I did.

I plan to create several of them, White and in different colors, for various occasions and uses.

The available LED bulbs have the circuitry to derive limited low voltage DC power for the LEDs from the high voltage AC. Wiring the fairy lights in series with the bulb's LEDs works out very well. The exiting chip LEDs remain in the circuit as the power supply expects their load and they are needed to ensure proper voltages and current. The excess light from the original LED chips is eliminated by covering them with a high temperature black paint. Note that the emitted light itself produces hardly any heat; even when block/absorbed by the paint. Further the overall operating temperature is reduced as a slightly lower voltage drop across the high power LED chips slightly reduces the wattage.

Step 1: Steps in the Making

Picture of Steps in the Making

In this project you are working with a 120vac device so be sure to take extra precautions. Be safety vigilant. Proceed at your own risk as we are modifying the insides of the 120VAC light bulb, during modification, testing and subsequent operation. The original manufacturer will not and I can not be held responsible, in any way, for you, your work, or the units you customize. That said working on it while unplugged, and exercising cause when first powered up you should be just fine.

  1. Acquire components
  2. Remove the globe from bulb
  3. Tape a mask around the LED chips
  4. Place a spray guard under bulb
  5. Spray black paint over LEDs
  6. Allow paint to totally dry
  7. Remove tape and guard
  8. Unsolder the negative wire
  9. Solder the Fairy light string into the open line
  10. Crumple up the string into the globe
  11. Replace the globe onto the bulb
  12. Screw it in & Light it up.

Given you have all you need and are clear on what you're going to do, This recreation can be done in less than an hour (not counting paint drying time).

Step 2: What You Need

Picture of What You Need

Required:

  • G25 LED bulbs with a clear globe, GE 3.5w or 5watt (Walmart, Home Depot)
  • Fairy Light string, which operates off batteries. on eBay
  • High temperature black spray paint (Home Depot) on Amazon

Tools:

  • soldering iron and accessories
  • shrink tubing 1/8"
  • flexible putty knife

Optional:

  • possibly some glue for final assembly
  • voltmeter for confirming voltage polarities

Step 3: Information About the Components and Operation

Picture of Information About the Components and Operation

The Fairy lights

Normally use 3 AAs (or AAAs) providing a low level DC voltage and in my case a current of 33ma (>1ma/led).

I think that this fairy light string is poorly lit due to limited current in order to get the 'Warm' off white color and/or to lengthen operating time so as to improve customer satisfaction. In the fairy-bulbs, I created, there is 4-5ma per fairy light LED. They look better (well lit, yet not bright) and are still very low power (<15mw each). In confirmation of this I pinched one between my fingers after lengthy operation, and could hardly tell if it was warmer than room temperature.

The strings I used have 40 LED lights. I have ordered some with 50 as well as 100 lights to try them out. I think 40-50 is perhaps best. I expect the string of 100 to result in dimmer lights but of course offsetting that with more of them; which may turn into more of a blur.

I recommend not using strings along with components that make them blink, dim or flash, as they would use some logic circuitry, which in turn have specific DC volt range requirements expected not to be conductive to this project implementation.

LEDs are intended to operate with voltage applied only in one direction. In the AC bulb there is circuitry which converts it's alternating current to direct (one way only) current. Be sure to at no point connect the fairy light LED string with the wrong polarity, as the resulting reverse voltage biasing could break down and damage the leds.

The Bulb

In my first test unit, utilizing a 4 LED chip 5w bulb, after modification I measured a 2 volt reduction across the four chips and a maximum temperature reduction of about 10 degrees Fahrenheit on the base metal heat sink (170 -> 160).

I have successfully used both the 3.5w and 5w version of GE's clear G25 bulbs. Their 4.5w version does not have accessible wires to allow an easy modification.

The 3.5w & 5w bulb used ~177ma through 3 & 4 LED chips respectively.

The GE's 6.5w bulb, while being 'higher power', they were so by having a larger voltage across more (8) LED chips; but a low current 111ma instead of 177ma. As it is the inline current that our string of parallel fairy LEDs share, the fairy LEDs are less well lit. So I have chosen not to use the 6.5W versions of the GE bulbs.

The resulting circuit

Reference the diagram above.
Note that the current that flows through each of the chip LEDs in turn flows through the fairy light string where the current is divided up among the mini LEDs as they are wired in parallel.

Step 4: Key Modification Details

Picture of Key Modification Details

All my comments here, and above, are relevant to the current 3.5w & 5w GE G25 bulbs and the fairy lights I have used. Matters may differ if you're using other specific components.

Here the 'step#'s refer to those listed in the section "Steps in the making" above.

step #2: Removing the clear plastic shell

Test the shell to be sure that it is indeed plastic, using a sharp knife. If the blade pressed against the bulb will not easily move side to side it is plastic. The edge of a blade will not bite into glass and so it will easily slide side to side.

I have removed glass ones, but I have also had them burst in my hands (gloves would have been smart). Due to safety concerns and likelihood of failure to separate it without breaking it, I definitely recommend against trying to use a glass bulb.

To remove the globe I ran a thin blade paring knife between the globe and the base. There may be a dab of silicone glue somewhere along its lip that needs to be cut through. Wedge a putty knife near the knife then get the knife wedge in the other side. Rock and twist them until the globe simply pops off.

You never need to press the knife in really hard, and to do so might result in a slip and you could cut yourself; so don't do it.

Step #5: Spray painting

Be sure to use high temperature spray paint (meant for grills or engines).

Spray 3 or four layers allowing complete drying between each (perhaps 15-20 mins).

Step #6: Total drying out of paint

Allow the paint job to fully dry, 12-24 hours.

I found that the smallest speck of less than 100% dried out paint will vaporize once the light is turned on, which then tends to create a pit for a pin point for light to escape. This is not necessarily a definite failure, given the amount of light escaping is much less than one fairy light led.

Step #8: Unsoldering the negative wire

On the bulbs I used the gray wire is the negative.

This lead is soldered to the LED chip PCB passing through a thick board and can be a little hard to unsolder and pull out. I recommend using a 40-50 watt soldering iron to do so. I also used the tip of a dart to leverage the wire up and out.

Step #9: Solder the Fairy light string into the open line

Cut off the control circuit/battery pack from the fairy light string. Reconnect them temporarily, turn them on and determine which lead is the negative.

Be sure to connect the fairy string's negative (cathode side) to the negative gray wire of the bulb. And the other to where you unsoldered that gray wire from. It is highly recommended to use shrink tubing over the solder joint between the wires. Alternately electrical tape or high temperature glue might be used to protect from an accidental short.

Step #11: Replace the globe onto the bulb.

There are tiny notches along the globes edge. When lined up the globe will pop on securely.

Step 5: Share Your FairyBulbs With Us

I envision different FairyBulbs being used for different occasions and purposes.

New Years & 4th July . . . . . . . . . Red, White & Blue

Saint Patrick's day . . . . . . . . . . . Green

Halloween . . . . . . . . . . . . . . . . . . Purple (Violet) & Orange

Christmas . . . . . . . . . . . . . . . . . . Multi-color or individual Red, Green & White

Party Time, Weddings . . . . . . . . . lots of White ones

Bug light, conversation piece . . . . Yellow

You are likely only going to find purple and orange fairy light strings in and around Halloween. All of the rest may be available any time and especially near Christmas. Otherwise you can wait for them to be shipped directly to you from China via eBay.

I look forward to seeing many 'I Made It' photos of various colors, utilized in many settings.

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Bio: Professional Software, Hardware, Systems Engineer for more than 40 years. Amateur Radio HAM (KI7NEW)
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