Three Candles

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About: The more mistakes I make, the more experience I gain.

"Three Candles" in Fourth of July attire.

Runs a few days on a charge using three salvaged tea lamp LEDs and flame lenses, one magnet, one reed switch, one 500mah LiPo battery and six 3D printed parts (five unique). Tilt it rearward and it lights, tilt it forward and it extinguishes.

We are using these as table centerpieces for our annual Fourth of July gathering. And if you celebrate the Fourth of July, we wish you a safe holiday!

Designed using Autodesk Fusion 360 and Meshmixer 3.5.474, sliced using Cura 4.1 and printed in Ultimaker PLA on an Ultimaker 2+ Extended and an Ultimaker 3 Extended.

Supplies:

I used the following supplies and tools:

  • Red and black 26 AWG stranded wire.
  • Electrical tape.
  • Soldering Iron and Solder.
  • Thick cyanoacrylate glue.
  • Wire Cutters.
  • Wire Strippers.

Step 1: Purchase, Print and Prepare the Parts.

I purchased the following parts:

  • One USB LiIon/LiPoly charger (https://www.adafruit.com/product/259).
  • One LiPo Battery (https://www.adafruit.com/product/1578).
  • One JST PH 2-Pin Cable – Male Header 200mm (https://www.adafruit.com/product/3814).
  • One reed switch (2 by 12mm, Gikfun 20pcs Reed Switch Normally Open N/O Magnetic Induction Switch Electromagnetic for Arduino (Pack of 20pcs) EK1621x2, available on line).
  • One neodymium magnet (12mm diameter by 3mm thick, local hobby shop).
  • Three salvaged tea lamp LEDs and flame lenses.(https://www.amazon.com/gp/product/B00T28FWVS/ref=ppx_yo_dt_b_asin_image_o00_s00?ie=UTF8&psc=1).
  • Three 100 ohm resistors.

I 3D printed the following parts at .15mm layer height, 20% infill, no supports:

  • Three "Adapter.stl".
  • One "Base.stl".
  • One "Candle, Short.stl".
  • Two "Candle.stl".
  • One "Cover, Rear.stl".
  • One "Tool, Pre-thread.stl" (optional, used to assist in cleaning the threads in "Base.stl").

To generate the tri-color base, I used the Cura 4.1 "Post Processor" feature (Cura Extensions, Post Processing, Modify G-Code menu) to pause the printer at both the 98 and 196 layer heights, changed the filament color, then resumed printing. Following the orientation of "Base.stl", I started with blue (for layers 0 through 97), switched to white (for layers 98 through 195) and finally switched to red.

Step 2: Wiring and Assembly.

The wiring for "Three Candles" is fairly straightforward.

  • Battery positive ("+") connects to the anodes of the three LEDs (LED1, LED2, LED3).
  • Battery negative ("-") connects to one lead of the reed switch (S1).
  • The remaining lead on the reed switch connects to one lead of each of the three resistors (R1, R2, R3).
  • The remaining lead of the three resistors connects to the cathodes of the respective three LEDs.

I wired and assembled "Three Candles" as follows:

  • Carefully bent one lead of the reed switch (S1).
  • Soldered the black lead of the JST PH 2-Pin Cable to the straight lead of the reed switch and a 60mm length of 26 AWG black wire to the bent lead of the reed switch.
  • Slid the reed switch assembly into "Back.stl", then using thick cyanoacrylate glue I glued the wires to the back for strain relief.
  • Soldered the three 100 ohm resistors (R1, R2 and R3) to the free end of the 60mm length of 26 AWG black wire.
  • Threaded "Candle, Short.stl" into "Base.stl".
  • Threaded the free end of the 26 AWG spool of black wire through the base and up candle short, then cut it to the length necessary to reach from the free lead of resistor R1 to the LED cathode lead.
  • Soldered the candle end of the 26 AWG black wire to the LED cathode lead.
  • Soldered the base end of the 26 AWG black wire to the free lead on resistor R1.
  • Threaded the free end of the 26 AWG spool of red wire through the base and up candle short, then cut it to the length necessary to reach from the red lead of the JST PH 2-Pin Cable to the LED anode lead.
  • Soldered the candle end of the 26 AWG red wire to the LED anode lead.
  • Soldered the base end of the 26 AWG red wire to the red lead of the JST PH 2-Pin Cable.
  • Tested the wiring by plugging the battery into the JST PH 2-Pin Cable and placing the neodymium near the reed switch and made sure the LED illuminated.
  • Pressed one salvaged flame lens into one "Adapter.stl".
  • Pressed the LED into the flame lens assembly.
  • Pressed the flame lens assembly into the candle.
  • Repeated this process for the remaining two candles.
  • Insulated exposed wiring using electrical tape.
  • Placed the battery into the assembly then connected it to the JST PH 2-Pin Cable to make sure all LEDs illuminated.
  • Placed the neodymium magnet into the base.
  • Pressed the rear cover into the base.

To illuminate "Three Candles" tilt it back, and to extinguish tilt it forward (a small tap may be required to separate the magnet from the reed switch).

And that is how I made "Three Candles".

I hope you enjoy it!

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