Thread: Furious Jack the JOL scarecrow

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With three days to go before Halloween I decided I wanted to revise my propane fired pumpkin from last year. This is what I came up with:

YouTube - Halloween Scarecrow with laser









YouTube - Halloween 2010

He's made out of cardboard and masking tape with a metal support structure. (3/4" waterpipe with a 'T' at the neck-- arms are PVC pipe and then I welded a platform to the top for the (real) pumpkin). Electrical and gas lines go up the 'spine'.

The heart is colored flexible foam with a couple LED's programmed into a 'beating' pattern. (That was surprisingly effective!)

I didn't turn the gas up as much as previous years (just because I didn't want to totally burn out the pumpkin too fast, but it ran just fine for ~3-4 hours until we closed down.

We had ~148 TOT's compared to ~150 last year, so basically the same turn-out. Everyone seemed to like the display. The approach to the house was dark (although the video makes it look *much* darker that it really was). Apparently it was spookier than last year because we has about ~10 younger TOT's "freeze up" about half-way up the path that we had to go outside to meet with candy.

-Clay

Love the laser effect , how did you do that ?

Originally Posted by Sychoclown

Love the laser effect , how did you do that ?

That's basically the 'laser vortex' effect. Usually it's accomplished by just pointing a laser (green ones are bright and cheap) at a front surface mirror mounted at an angle on the shaft of a motor. The motor spins and depending on the angle of incidence of the laser you get a cone of light. There's some fog in the air which makes the beam visible and renders the 'vortex' look.

In this particular case I had an RGB laser projector so I used a microcontroller to plot two sine waves out of phase with the internal DAC of the micro and draw a circle. That's sort of the equivalent of using a hammer to kill and ant, but hey, use what you got.

If anyone can look directly in to the 'beam' part of the vortex you want to be careful with the laser exposure time to make sure you can't cause any eye damage. Thankfully with the vortex effect the exposure time is very brief because the beam is moving in a circle rapidly so you're really only being exposed to the light for the amount of time it takes to pass over the pupil. There's information on safe exposure times for lasers online-- you can look into "audience scanning" with lasers if you want to find more info.

-Clay