# HOWTO: safe LED lighting for haunted houses (technical stuff)



## thrilltainment (Apr 8, 2010)

The trend with LEDs is becoming more popular in our daily lives (stop lights, TV, computers, instrument panels, etc...), in this post I will try to convince you that LED lighting is way to go for 99% of your haunted house lighting needs. This post isn't for promo purposes but simply to inform about safe lighting practices and to illustrate the benefits of placing more focus on lighting in your haunt. Please feel free to post any technical questions you may have and I'll try to the best of my knowledge to answer them.

*Why use LEDs?*

Safe --- LEDs are low voltage and generates very little heat, reducing risk of fire dramatically, this reason alone should convince you to use LED lighting in haunts. You can also hide LEDs in virtually any material w/o worrying it'll catch on fire.
Durable --- LEDs typically won't shatter when dropped, there are no moving parts or hollow spaces. LEDs can even be made water resistant or water proof with the correct type of casing.
Energy efficient --- the amount of light per watt of power used is significantly better than traditional incandescent lights. This year, LEDs will exceed the efficiency of compact florescent lights (the curly light bulbs).
Environmental friendly --- there are no toxic substances in the LED, there is mercury in fluorescent lighting. In case you do manage to break an LED, you won't have to worry about dealing with hazardous materials.
Easier to install --- Although I don't know all the local fire codes, I don't believe low voltage lighting wires require running it through conduit, this will save a lot of time when running your wires around.
Directional light --- LEDs inherently emit direction light, making them great spotlights.

*Why are people still using the traditional bulbs?*

Perhaps their haunt was built way before LEDs got popular, it was probably a lot of work to install the electrical system and they haven't felt the need to switch over
LEDs may seem like unfamiliar territory because they come in so many types and very few (until recently) are compatible with traditional light fixtures
For making your own LED lighting system, it does take some basic technical understanding of electricity.

*LED Basics*
LED stands for Light Emitting Diode, this is a type of semiconductor that will light up when a voltage is applied to it. Because LEDs are diodes, polarity matters --- that is, in order for the LED to light up, the positive voltage must be applied to the anode and the negative voltage must be applied to the cathode. LEDs typically light up with only 1.3V - 4.0V applied to it, this voltage is specified in the LED's documentation and varies between colors and models. One important thing to understand is, simply hooking up a small battery to a bare LED is NOT good practice. This is because your battery is not limiting the current that will be applied to the LED. The LED may still light up, but you may be significantly reducing its lifespan or burning it out. If you ever buy a really cheap key chain LED light (for about $1) and open it up, often you'll see a bare LED straddling a 3V button battery --- this is as cheap as it gets, the LED will light up but not reliably (you'll probably notice in the long run your LED may not be as bright as it used to be). The proper way to light an LED is to have a RESISTOR in series with the circuit to limit the current flowing through the LED (I'll explain how this works below). For more details, go to Wikipedia: Light-emitting diode - Wikipedia, the free [email protected]@[email protected]@/wiki/File:RBG-LED.jpg" class="image"><img alt="RBG-LED.jpg" src="http://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/RBG-LED.jpg/225px-RBG-LED.jpg"@@[email protected]@commons/thumb/c/cb/RBG-LED.jpg/225px-RBG-LED.jpg

*Differences between LEDs and traditional lights*

Polarity matters: if you reverse the polarity on an LED, it just won't light up
LEDs are not dimmable in the same way that traditional lights are -- will go over this in more detail below
LEDs run on low voltage, even if you have LED bulb that screws into traditional 110V or 220V sockets, there is circuitry inside that steps down the voltage

*How to light up a SINGLE LED from a 9V battery properly*
Assuming you have a single RED LED with a turn on voltage of 1.7V and handles up to 20mA of current (usually these specs are on the website from which you purchased the LED or on some type of packaging that came with it), here's how you get it to light up reliably (we require some basic electronic principles).

With a 9V battery, 1.7V will be dropped across the LED, that means 7.3V still remain --- this voltage will be dropped across a current limiting resistor, which is in series with the circuit. Since we want at most 20mA travelling through the LED, that also means at most 20mA will travel through the resistor. By basic Ohm's Law: Voltage = Current * Resistance we get: 7.3V = 0.020A * R, if we solve for R, we get 7.3/0.02 = 365 Ohms. This means you want to use at LEAST this resistance in your circuit because this limits the current to at MOST 20mA. You probably won't find an exact valued resistor for what you calculated, just use the closest standard value that is HIGHER than what you calculated. More resistance = less current. Below is a simple diagram and a really useful tool for calculating the resistor value needed for your LEDs.

http://www.pcboard.ca/kits/led_notes/









You'll realize most of the 9V we started out with was dropped through the resistor (7.3V) and only a small portion of it (1.7V) was through the actual LED ---- this is pretty inefficient as most of the energy was simply burned off as heat through the resistor and not as light. A more efficient way to do this is hooking up several LEDs in series on the same circuit:









In the picture above, 3 LEDs are hooked up in series, meaning 5.1V (3 x 1.7V) is dropped across it and only 3.9V needs to be dropped across the resistor. By the same calculation method above, you'll get 3.9V = 0.020A * R, and solving for R we get 195 Ohms. Of course there is a limit to how many LEDs you can put in series, the total combined voltage drop MUST be less than your voltage source. If you're running off of a 9V battery like in the diagram, you'll also want to account for the battery's voltage lowering as it starts to run out of juice. Say the battery can potentially drain down to 8V, then at MOST you can hook up 4 LEDs in series.

*Dimming LED lights:*
Traditional light bulbs dim out when a lower voltage is applied to it. This will work for LEDs to SOME extent but you won't a very smooth transition between ON, DIMMED, and OFF. The brightness of an incandescent light is proportional to the voltage applied to it. The brightness of an LED is proportional to the CURRENT running through it, however this is much more difficult to control. There are two ways of dimming an LED, one way is simpler and less efficient, the other is more complex but very energy efficient.


*Simple but inefficient:* if you add a potentiometer (a variable resistor) to the circuit above, you can throttle the current through to the LED.
*Efficient but more complex:* LEDs work more efficiently when they are either fully ON or fully OFF. If you're switching the LED ON and OFF very fast (more than 100 times per second), you won't be able to see the flickering. During this ON and OFF cycle, if the ON time is more than the OFF time, your LED will appear brighter. If the OFF duration is more than the ON duration, the LED will appear dimmer. By varying the relative pulse width between ON and OFF, you'll be changing the perceived brightness of the LED, kind of like taking an average of the light output. This technique is called "Pulse Width Modulation"










Most low voltage LED dimmers work in this fashion. For example here:
http://www.ecolightled.com/product/led_pwm_dimmer_inline_12V/pwm_led_light_dimmer

*Using a LED lighting system in your haunt*
Most low voltage lighting systems on the market are using 12V, it's pretty standard because you can find 12V in a bunch of places:

Standard wall warts (you can rip it off some existing appliance or buy a universal one from Radio Shack)
Car batteries
Regulated power supplies specially designed for LEDs
Most of your haunt probably is using 110V AC power --- you'll need to find a way to convert it down to 12V DC, most of the time people can just go to Radio Shack and buy a 12V power supply. Just make sure the the total current being used by the LEDs do not exceed the current rating of your power supply. For example, if you have a 2.0A power supply at 12V DC, and each LED you have uses up 20mA, that means you can took up at MOST 100 of these LEDs in parallel. Once you have your 12V source, you can use terminal blocks to distribute the power to your individual LED lights.









One great thing about low voltage lighting is the ease of installation --- since you're not running much voltage (or current), you won't need really thick wires (unless you're running your wires several hundred feet). For the most part, 24 AWG speaker wire is a cheap and effective way to light up your LED system. You can also use ethernet or telephone cable, pretty much any wire around the house will work. For wire management purposes, it is recommended to use one power adapter for every few adjacent rooms instead if wiring up an entire haunt with just a single adapter.

If I haven't addressed any technical part to this point, please comment below and let me know.


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## thrilltainment (Apr 8, 2010)

*lighting techniques with LEDs*

Now, for the the lighting techniques: this part is more subjective and everyone's opinion may vary --- discussion is welcomed

I want to start off by asking the rhetorical question: "What good is your $5000 animatronic if no one can see it?" Many people spent tens of thousands of dollars on building their set, awesome animatronics, but pay little attention to the lighting. I dare to say that lighting can make or break your scene. It brings out what you want your visitors to see and hides what you don't. It's great for misdirection, mood setting, and showing off all the hard work you went through to put your haunt together! I've been through several haunted houses on tours where we go back during the lights-on saying "I wish I had seen that in the dark, I didn't even know it was there!" On the contrary, you also don't want to walk in to a haunt where you CAN see everything, then there's no mystery --- this is why LEDs are perfect, they're not as bright as traditional lights, and can highlight JUST enough of what you need, nothing more and nothing less.

LEDs are also great because they come in so many different colors and tend to give more of a pure color than your traditional par cans with gels over them. Because LEDs are directional by nature, you can use it as a spotlight for many of your scenes.


A single LED enclosed in a tube can pinch off the light spread making a solid spot, this is great for highlighting props or casting creepy shadows
Several LEDs with a wider dispersion angle can give a nice soft flooding effect to a scene, you can get a nice glow in a corner of a room
There are many high powered LEDs on the market now (1Watt or even 3Watt), just a single one of these can flood an entire scene with color.

For completeness, I'll list a few examples of where to use certain colors (some may be quite obvious):
Reds: dungeons, hellish areas, any scene with fire, blood, or guts
Greens: alien scenes, labs, jungles, graveyards, creates a creepy mood
Blues: cold mood, freezer, water scenes, graveyards, futuristic scenes
Amber: this color makes anything look old (like in old color faded pictures), great for attics, barns, warehouse, also use with fire scenes
White (cold): almost the same color as fluorescent tubes, use in offices scenes, or to highlight props that need to show full color
White (warm): similar in color as a traditional light bulb, use it to make your scenes more natural looking, also use to highlight props that need to show full color

Remember if you're highlighting with any of the colors other than white, you'll most likely wash out the colors you used to paint your scene. Often times your scene detail make look awesome when you have normal lighting on it, but if you hit it with a red light, everything in that scene will be some shade of red.

I suggest to detail your set in actual haunt lighting --- this way you'll know what the final product actually looks like (or at least switch between your normal light and haunt light during the detailing process).

Alright, I know this was a pretty long post and really thank anyone who took the time to read this. If I had left anything out, let me know and I'll try to offer my advice as best as possible. Thanks!


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