32 December 2014
BUILD IT YOURSELF
By Ron Newton
I’ve been married for 53 years now, so finding my wife
a Christmas present becomes more of a challenge. It’s
not like I can't afford to go to the store and buy
something. It’s just that I was raised believing that a
gift should come from the heart and be something
handmade. I'll never forget when I was eight, my dad
made me a plyboard jeep with a 30 caliber machine
gun mounted in the back that was made out of a
cardboard shipping tube.
Due to allergies in the family, we can’t have a live Christmas tree, and I’m getting too old to put up a fake one. My grandkids are all older too, so now I’m waiting for great-grandkids. Thumbing back through some old issues of Nuts & Volts, I came upon an issue that had a Christmas tree made out of LEDs. Searching the Internet, I found
several methods for making a cone shape tree utilizing different techniques. While
there are a plethora of kits available, I decided to come up with my own (Figure 1).
I added a pryoelectric infrared (PIR) sensor for a proximity detector, along with a
microphone circuit which detects music and then flashes accordingly to the beat.
The tree has a four inch square base and a height of 10. 5”. There are eight
columns which have 56 LEDs. The top LED is a tri-colored unit that changes colors.
The LEDs are multiplexed to save power, and appear to be on all the time even
though they’re not.
Let me digress. In 1948, Southern California Edison switched from 50 Hz to
60 Hz. I remember this well as all the electric clocks had to be discarded, along
with many motors. Using 50 Hz and incandescent bulbs, no one could see the
flicker since the filament could not cool off that fast. Keep in mind that when using
a 50 Hz alternating current, there is a period of time (100 times per second/zero
crossing) when the power is off. However, in 1938 when fluorescent bulbs became
popular, a noticeable flicker could be observed that drove people nuts.
; FIGURE 1.
BUILD THE 3D CHRISTMAS