Wednesday, August 25, 2010

Ever Elusive Haunted Lantern Project

I'm sure most folks have seen the old kerosene lanterns often used in haunts.  There are some great simple hacks to make them a bit more haunt reliable and safe such as this and this.  There are now LED flickering candles you can buy at most craft and dollar stores, but they are pretty weak.  There is infuriating little information on the internet about how to go about building a simple flicker circuit that makes much sense.  Either the circuits are too complicated for the novice electrician, or poorly developed by folks that don't know what they are doing.  I've spent months trying to figure out a simple and effective circuit to fit in the three lanterns I picked up for $5 a piece at the local discount store.  

First, I would not have gotten this far without a nod to these "pioneers" of yard haunt LED ingenuity.  Spooky Blue has the "Spooky Blob", but I wasn't comfortable with the circuitry that seemed possible to burn out the LEDs.  I found this tutorial on linking flashing with ultrabrite LEDs for lighting pumpkins, but again I don't trust the circuit without resistors as I almost instantly blew out an LED hooking it up to a 9 Volt battery.  LEDs run at anywhere from 2.2 Volts to 3.5V or sometimes 5V, I never found any 9V examples during my research.  Also, most haunt related sites offering how-tos seem to be pretty dated for the current technology, again, looks great, but no how to-the link is down.  

I wanted the power and compactness of a 9 Volt to run a series of paired LEDs and found this circuit wizard to be very informative.  I entered in 9 for the battery voltage, 3 for diode forward voltage, 20 for mA and 10 for the number of LEDs.  I used the second set of plans or array design. 

 I then took a breadboard for easy experimentation after a horrible, awful, frustrating evening of trying to temporarily hold the circuit components together with electrical tape (never, ever, make that mistake).  I used 150 Ohm resisters and put them in before pair of LEDs, I have no idea why the wizard shows then after them, but then again, I am no electrician either.   I then inserted a flashing LED then a superbright LED before connecting the two to the negative terminal part of the breadboard and repeated with five pairs. 

 The LEDs flash at fixed but different rates from one another creating a random looking "flicker" like a candle sputtering.  The actual LEDs should not be visible to the viewer, but set back in the bottom of the lantern out of view, otherwise the whole thing looks like a flashing Vegas sign.  I will hot glue some small mirror fragments in the top of the lantern to really bounce the light around and attach a switch to the circuit to mount in the Kerosene fill port for ease of use.   

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