Flan jar lid

flan-jar-lidNowadays people are familiar with recycling. But some people forget recycling is only the third alternative in “reduce, reuse, recycle.” The goal of this project is to reuse small glass jars instead of tossing them into glass recycle.

The jars came from an eight-pack of flan in little single-serve portions. The jars were sealed with a layer of foil, which was sufficient to preserve the flan until the expiration date, but the foil top was not reusable.

In order to reuse these jars, I need to make some lids. At first I thought a simple revolve would do the job – draw the profile of a lid with a lip, revolve it 360 degrees, done! Sadly it wasn’t that easy.

Problem #1: neither ABS nor PLA were flexible enough to make a practical lid. What I had drawn up is the shape of a Tupperware lid but my material did not have the flexibility of Tupperware lids. I thought this was solvable by making the lid precise enough so that it only needed a tiny bit of flexibility to work. That’s when I ran into the next problem…

Problem #2: The flan jars were not perfectly round and varied from jar to jar. This was perfectly acceptable for their original usage of sealing with a foil top, but tremendously inconvenient for me! It’s not practical to try to match the precise shape of each individual jar just to make a lid.

To work around these  problems, I switched the design so that the lid slides on to the jar sideways. Half the lid is rigid, reinforced by a strong lip to hold on to the jar. The other half has a small lip at the far end keeping the lid in place. The lack of a strong lip gives the lid a tiny bit of flexibility, so the small lip can be bent out of the way and the lid can slide off the jar.

The lids make the jars useful for holding small tools and parts.

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Shade for the Garage Door Opener

blindersAll modern garage door openers have a safety feature: a small light beam to detect objects that might be in the way. Most of the time this feature is unobtrusive working in the background for my safety.

Occasionally, though, the sun would be at an angle that blinds the beam receiver. When the sensor is blinded, the garage door opener defaults to safety and behaves as if there was an obstruction in the door. Great for safety, not great for actually getting the door closed. What we needed was a sunshade.

The tolerance requirements were very relaxed relatively to the other projects. I didn’t even need the precision of a caliper, a ruler was enough to get me in the right ballpark.

I rotated the shape 90 degrees, so that it faced down, to enable easier printing. By doing this the shape could support itself as the 3D printer built up the layers, no need to waste material printing supports. Aligning the object in this manner also resulted in a cleaner inner surface for the tube.

At the time of this project, my 3D printer was loaded with transparent filament. I decided to perform a test print even though a translucent shade would be counterproductive to the goal of shading light. I thought I’d make a few test prints and iterate to the final design as my 3D projects usually do, and load a different filament for the final print.

My plan was foiled by the realization it fit and worked right off the bat. Even though the end result is not opaque to light, I suspect it breaks up enough of the sunlight. If the transparency ever becomes a problem, I can always spray paint the exterior of the object.

Good enough! I declared the project complete and moved on to the next thing on the to-do list.

Update: I’ve printed and installed an opaque replacement.

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Worn AA Batteries Get a Second Life

battery-tray-exploded-viewThe “Duck light” project earlier was a lot of fun, crafting an object to be lit with a little LED tea light. I liked the result so much I kept it lit around the clock, which led to the obvious next problem: battery life.

These lights came with a standard CR2032 lithium battery good for 2-3 days of continuous use. Replacement batteries can be found for less than a dollar, but that’s almost as much as the cost of the entire light! I embarked on a project: find a better way to keep my lights glowing.

Online search found some basic details on CR2032. The full power voltage is 3 volts, conveniently a multiple of the ubiquitous AA battery’s 1.5 volt. More interesting, however, is that the quoted minimum voltage is 2 volts. Most AA-powered devices would stop working well before an AA battery drops to 1 volt, which implies that a “spent” AA would still deliver sufficient power for the tea light LED.

With this research in hand, I proceeded to design and 3D-print a small battery tray as simply and inexpensively as possible. Normally an AA battery tray has metal springs to push against the negative end of the battery. My project takes advantage of the fact the 3D printed plastic is flexible, and print a curved arch to provide this holding force.

I need something at each end of the tray to complete the circuit. One end is easy: I pulled the LED component out of the tea light base and used pliers to shape the wires into a Y shape to connect the battery terminals. At the other end, I used a piece of aluminum foil from the kitchen. Normally this is a bad idea because a thin foil of aluminum can’t carry much current, but it should be fine given the extremely low power flow of the LED.

To make the base more presentable, add a cosmetic shell to cover the battery tray and provide support for whatever we want to keep lit, and voila! A small lighted base for any purpose.

I had a pair of AA batteries that had been in my Xbox One wireless controller. I received “battery level low” errors for about a week before the controller refused to turn on at all. Yet these batteries were still powerful enough to light up the LED and keep them lit for many days.

A cheery light powered by batteries that would have otherwise been thrown away. Success!

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