Thursday, May 7, 2020

More This is What You Can Do With a (Tall) 3D Printer

Another Lamp!

Ever since I made the first lamp that my son took to his dorm room in college, my wife has been after me to make one for her. COVID-19 isolation has granted me some time to get caught up on projects like this...

First, The Shade

I created the pattern using ChaosPro and saved a sequence of images. The shape is a power 3 Julia set fractal with one of the parameters swept from a negative to a positive value. I imported the image sequence from ChaosPro into ImageJ and saved it as an STL file, then loaded the STL file into PrusaSlicer and scaled and sliced it to fit on UMMD.  It was printed in 0.25 mm layers using transparent PETG, with 6 solid bottom layers, 3 perimeters, and no infill or top layers. If I recall correctly, it took about 24 hours to print. It is 503 mm tall and weighs 430 grams.

One of the images from ChaosPro that was used to make the lamp shade.

The shade is 503 mm tall, transparent PETG.

The top of the shade.

The surface of the shade has a very interesting texture that results from the limited resolution of the math that generates the fractal shape. There were a LOT of very fine cob-web like hairs because I used PETG to print. I pulled/clipped off the larger ones and "disappeared" the finer ones with hot air from a heat gun. There's still a little cleanup left to do.

After printing I cut a hole in the bottom of the shade to match the diameter of the LEDs on the circuit board from the light bulb. 

The hole in the bottom of the shade matches the diameter of the LED board from the light bulb.

A test using this shade with a long warm white LED bulb.  It has a nice look to it, but will need some work on the base.  I may make some of these.

The Light Source

I used a wi-fi controlled Feit Electric multicolor bulb that was rated for 1600 lumens. I took apart the bulb and found the usual two-circuit-board construction- one for the control electronics and the other for the LEDs. The base of the bulb is made of aluminum and acts as a heatsink for the LEDs.

This is the bulb I used.  On sale for $17 when I bought it.

LED board from the lightbulb. This board plugs into the controller board using the two 4 pin sockets on either side of the slot. The slot is for the wifi antenna that stands off the controller board. The blob of putty was covering the controller board- I suspect it was intended to be thermal insulation to protect the controller from the heat of the aluminum heatsink in the base of the bulb. The six big LEDs around the slot provide all the colors, the rest are for white light.

Inside of the bulb, putty and LED board removed - the controller board fits in the plastic covered aluminum base.  The white thing in the center is the wifi module. This board connects to the LED board via the two sets of four pins above and below the wifi module.

I wanted the light source to reside at the very bottom of the shade, pointing straight up, so the entire shade would be lit, and so that the light shining through the open top of the shade would make a nicely shaped pattern on the ceiling. That meant I had to separate the circuit boards from the light bulb and figure out how to mount them in some sort of base for the lamp. I also had to figure out how to fit some form of heat sink into the base so the LEDs wouldn't burn up.

The Base

The base was designed to hold the two circuit boards and heatsink.  It is designed in two pieces- a top plate to which the LED circuit board and heatsink mount and the bottom that holds the control board and power switch so the lamp can be turned on and off even if wifi isn't working properly. The bottom of the base is open to allow some air flow, though there probably won't be much. Time will tell if the heatsink I made is adequate.

Prototype of the base to check fit.  I printed this while I waited for delivery of the white PETG that I intended to use for the final design.

Top plate prototype.

The top plate has a hole that's just big enough for the LEDs to fit. The LED circuit board is trapped between the printed top plate and the aluminum plate heat sink. I put a couple dollops of heat transfer compound on the LED board before final assembly. 

The final base with LED board in place.  Notice the brown spots where the printer deposited charred blobs of PETG. Fortunately, they are covered by the shade.

Underside of the base.

Wiring between the controller and LED boards.  The aluminum plate is the heatsink for the LED board.

Clean looking back of the lamp.  I think the power switch came from a coffee maker.

Here it is.  The shade is attached to the base with some clear silicone.

The LED board has two four pin sockets to connect to pins on the controller board. I soldered wires to the controller board pins, covered them with heat shrink tubing, and then inserted the stripped wires into the appropriate connector holes on the LED board. Then I squirted a drop of hot-melt glue on the back of each connector to keep the wires from pulling out.

The Result

I am very happy with the way this turned out, but I'm already thinking of some improvements I can make in future projects like this one. First, PETG is good material to use for the shade, but white PETG is not so great for the base.  PETG has an annoying tendency to build up on the nozzle and then leave charred globs on the print at the worst possible locations, usually on the front of the print where it will be seen. Maybe I need to work on that nozzle wiping project a bit more... I think dark colors should be OK. I want to add some weight to the base to improve stability, too.

I'll probably print with the appropriate sized hole in the bottom of the shade for the next one, instead of cutting the hole after-the-fact.

The image projected on the ceiling by many LEDs shining up through the opening at the top of the lamp shade.

The lamp makes a very nice pattern on the ceiling as expected, and lighting from the very bottom really does light up the entire shade.  When set for white light at full brightness, it's almost too bright.  Fortunately, you can dim it via the wifi app for iPhone and Android.

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