Monday, December 28, 2015

A Luminary

Actually a few luminaries.  It has been a tradition in our family to have luminaries lining our driveway and entrance during Christmas and often also for new year.  A luminary is basically a  brown lunch bag with about two inches of sand and a candle.  It usually works quite well and is a nice touch to holiday decorations.  However bad weather can make this challenging and it sometimes is difficult to get the correct candle at a reasonable price. 

This year while teaching my STEM classes I had an idea of how to solve the candle problem.  The first exercise in my STEM class is for folks to make a throwie.  A throwie is basically a LED and a coin battery (usually a CR2032) taped together being mindful that the longer positive lead of the LED touches the positive side of the coin battery.  My STEM course manual has directions if you cannot figure it out from this description.  It provides a sense of accomplishment for the students and demystifies touching wiring.  The history of the throwie was that makers also attached magnets and they would throw it at metal structure to decorate them.  We usually place tack on the back and they place it on their id badges.  I wondered if such an arrangement would help with the candle problem in the luminaries.

The first  hurdle was that any LED would not do.  It would have to be large 10mm and would have to flicker like a candle.  I experimented with many a blinking, flickering LED and discovered the best candle like LED at, a great site for LEDs and other geekie stuff.  I experimented with a few and selected a 10mm white flicker.  It was perfect.  I tested it one night with a paper lunch bag and sand.  I secured the LED to the battery with electrical tape and shoved the leads into the sand until only the bulb was showing.  It flickered nicely but simply was not bright enoungh.  Next night I used two CR2032 coin batteries in series, second battery positive (+) side was against first battery negative (-) side.  Fortunately this did not blow the LED but made it considerably brighter.  Please be careful when you first test yours - since LEDs may differ - wear adequate eye protection.   Here is a picture of them in our driveway.
Not a great picture but you get the idea.  Although they dim every night a bit, they are still glowing enough to see from the street after 4 days.

I am working on a bunch of new posts including benchmarks for the UDOO Neo and the CHIP computer. Hopefully I will do better in the new year.  The best to all of you in the new year!  Later!