Wednesday, July 8, 2020

To a Hammer, Everything Looks Like a Nail

A couple years ago I installed a timer switch on my front porch light so it would turn on at dusk and off at dawn. It was one of those smart switches that knows what time it is and when the sun sets and rises and even keeps track of daylight savings time. The light uses two candelabra type bulbs and is about 12' (almost 4m) off the ground. At about the same time I installed the timer, I installed a couple LED type bulbs because they are supposed to last 20 years and I don't like climbing up on a ladder to change light bulbs that are 12' in the air.

Well, it's two years later and one of the so-called 20-year LED bulbs failed. I wanted to replace both of them with yellow bulbs because the white light attracts bugs, and the bugs attract spiders, and the spiders make webs and catch the bugs and leave things looking very messy. I found a couple candelabra base yellow LED bulbs at Home Depot, got out the ladder and went to install the new bulbs.  

The fixture hangs from a chain, way up in the air, and requires two hands to get it apart to install the bulbs. That means I'm up on a ladder, with two hands on the fixture and none on the ladder, not a good situation. I unscrewed the bottom part of the lamp fixture, and it and the glass then came down, granting access to the bulbs. I had forgotten that the glass doesn't actually attach to the bottom part of the fixture and ended up dropping it. Oops!

So now I had to replace the glass, an impossible task because that stuff is not standard and even if I could figure out who made the lamp, they've long since stopped making them or stocking the glass parts. So my choices were either buy a whole new fixture or make my own replacement for the broken glass. Being a cheapskate and 3D printing type person- you know the type, every problem can be solved with a 3D printer- and having recently made a nice lamp using some beautiful edge-glow glass PETG filament from Keene Village Plastics, I decided to try using the stuff to make a replacement for the broken glass. If it didn't work, I'd only be out about $1 worth of plastic and a couple hours of print time and I could always replace the whole fixture.

After I finished cleaning up the broken glass, I made a couple quick measurements of the fixture and went to work. The only dimensions that matter are the diameters of the top (222 mm) and bottom (102 mm) parts of the fixture, and the distance between the top and bottom (180 mm) when the fixture is screwed together. In Fusion360 I created a profile of 1/2 of the glass using a few straight lines and a spline curve, then revolved it 360 degrees to make a solid of the correct size and shape, then exported the STL file. I sliced it with 2 perimeters with 0.5 mm line width and 0.3 mm layers, no top, no bottom, and no infill. It literally took less than five minutes to design and slice.

The print took about 3 hours at 50mm/sec. Judging by the surface of the print, I'd say 50 mm/sec may be pushing the speed a little high for this filament. No matter- it will be 12' in the air and no one will ever get close enough to see any imperfections. The whole thing is pretty flexible, but rigid enough to maintain its shape as long as I don't screw the bottom of the fixture on too tightly.  

The print doesn't look particularly transparent, but it actually lets a lot of light through. 

And here it is installed, with the new yellow bug lights on:

Yes, those are bugs sitting on it! So much for the idea that yellow light bulbs don't attract bugs...

Next project: clean all the spider webs and dead bugs off the porch walls and ceiling.


  1. This is very cool! Keep up the posts! :)

  2. Have you checked that they are real amber leds? Most leds bulbs are blue leds with phosphates to change the color (Phosphor-converted amber LED) and still have a lot of emissions in the blue-green spectrum region, even if they look yellow

    This is a good reference about the different light systems:

    1. I have no idea what the LEDs are inside the bulbs, but I suspect they are the things that look like filaments that light up because the bulbs are very light weight and don't seem to have any sort of power supply built in (like the old Sylvania bulbs did). The envelope is yellow and that may be the main source of the yellowness. I would guess it's a warm white bulb that's been placed inside a yellow envelope.

      Yellow light doesn't repel bugs, it just attracts fewer of them than white/blue bulbs. It does appear that there are fewer bugs around the light than there were when the white bulbs were in the fixture.


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