Halloween Hacks: Flickering Jack-o’-lantern
posted Oct 23rd 2011 6:43am by Brian Benchofffiled under: contests, led hacks
The dollar store is always a great place to find some weird stuff, so when [jethomson] found a flickering Jack-o’-lantern, he thought it would make a great project for the 74xx logic competition.
Instead of using the flickering incandescent lightbulb that came with the blinking pumpkin, [jethomson] decided to rebuild a blinking circuit around a 74HC14 Hex inverting Schmitt trigger IC. The chip was used as a relaxation oscillator by adding a resistor and cap from the input to the ground. After a bit of component selection and some calculation, he had a red and blue LED blinking at 2,6,9, and 15 Hz.
The result is a seemingly random pattern of light that looks like a ghostly blue after image of the handheld Jack-o’-lantern. While it may not be one of the most complex builds for the 74xx competition, it gets points in our book for originality.
Although [jethomson] says his camera doesn’t pick up his project very well, he did post a video of the Jack-o’-Lantern in action. Check it out after the break.
I wouldn’t say using that relaxation oscillator circuit is very original because it’s in the datasheet. However, using just the 74HC14 and mixing several frequencies to get a flicker effect might be. The closest I found was someone who used an LFSR. My idea was to use non-harmonic frequencies to get a non-periodic waveform, but ultimately I settled on using frequencies that created an effect I liked.
Here’s a link to the article:
7400 Competition — Flickering Jack-O’-Lantern