This will be a fairly technical discussion and I hope it will demystify electrical usage in indie-film-making, as well as ensure your safety! I recently purchased a flicker box from Magic Gadgets. The male and female connectors were round-shaped and not the standard wall plug we see on orange extension cords. Plus, the box ships without its own power cord; therefore, I needed to make one. One of Grip Tips' first videos on their YouTube channel was on making your own stinger (e.g., power cord). Prior to jumping in, I wanted to do some more research to ensure I wouldn’t electrocute myself. This post is a compilation of that research. Stay safe!
Before we get started, it’s important to understand some key electrical terms:
Hertz (Hz): Direction of power with changes in seconds, 50Hz (Europe) or 60Hz (U.S.)
Voltage (V): The potential of the circuit (110-120V or 220-240V). Think of it as the power’s pressure. Voltage = Watts / Amps
Wattage (W): The total amount of power delivered at any moment. Watts = Amps * Volts. 1,000W (Watts) = 1kW (Kilowatt).
Amperage (A): The volume of power per second, e.g. power’s current/speed of flow. Amperage = Watts / Voltage
Ohms = Resistance, e.g. the “diameter of the power pipe.” Ohms = Volts / Amps
Gauge (ga) = The thickness of the power cable. Household wiring is typically 12ga with hardware store power cords (aka “stinger”) often offered in 14- or 16-gauge.
The thickness and length of the stinger will determine how much load it can take over distance. For example, a 100 foot 16ga orange extension cord will only take 500W until it starts warming up/melting. If you connected that cord to an Arri 1K and expected no issues, you should take a basic math course. From a safety perspective, select Underwriters Laboratory (UL) rated cords, preferably at 12ga with three conductors (12-3 SJOOW). The only place I have found these rated cords, black in-color at low cost, is at Menards.
Prime All-Rubber Cord 12/3 AWG 15A-125V-1875W 50- or 25-foot lengths
If you plan on making your own, please understand the difference in connectors. The typical 3-prong outlet on extension cords and in our home receptacles are NEMA 5-15 (15A). To support a Mole-Richardson 2,000 Watt (2K), you would need a 20A, straight-blade NEMA-5-20 plug connected to a 20A-rated stinger; thus, these two NEMA plugs are designed to be incompatible due to the difference in amperage. More than likely, the 20A connector will be a NEMA (L-) twist-lock connector as found in generator extension cords. To create the power cable for the Magic Gadgets Flicker2D box, I used Legrands (15A) NEMA 5-15P and 5-15R receptacles with a few feet of Lowes’ bulk 12/3SJ00W power cord. Installation was a snap with a screwdriver, a razor blade and some wire strippers. I even applied Raychem Heat-Shrink Tubing (600V, 10a 2AWG) with a heat gun to help protect the cabling from connector rub.
It’s important to understand the maximum load for your lighting package. For the rest of this tutorial, we will focus only on AC-powered, 60Hz (U.S.), 110-120V lighting packages at 1,000 Watts (1K) or below. You may hear the following slang, that denotes the lights’ size based on their output (Wattage). To facilitate safety and forego overloading of extension cords, I have added the general Amperage to a few lights:
120W Household Bulb: 60W (.5A)
Inkie: 150-250W (~1.7-2.1A)
In-Betweenie: 300W (2.5A)
Tweenie: 650W (5.4A)
Baby or Ace: 1K (8.3A)
Junior: 8” 2K (16.7A)
Studio Junior: 10” 2K
Senior: 5K
Tenner: 10K
For larger lights, locate a 20A outlet and avoid GFCI outlets. A good place to locate a 20A outlet is under the kitchen sink near where your garbage disposal is connected. An alternative is to locate the breaker box, identify a 20A fuse and use a testing plug to identify its find its location within the house. For this task, it’s best to carry a flashlight and some masking tape with a pen to mark the breaker’s fuse. The homeowner may appreciate the additional “gaffer value” you are adding.
Larger HMI lights, 4K and upwards, are daylight-balanced and require a bulky ballast for operation. Lest we also forget a large, 220V power generation source. Tungsten-balanced lights are usually 2K and below with some exceptions. Baby 1K’s (120VAC) can be plugged into a wall-outlet without much fan-fare as its drawing 8.3A. A 2K will pull ~16.6A on a 120VAC circuit. Remember, that any length of cabling will not only drop output, but could be rated for only 15 Amps (or less)! Expect 1 .22 volt drop on a 25 foot cord. As an aside, do not run electrical parallel to audio cables. To prevent recording interference, and if necessary, cross both cables once (+) at 90-degree angles.
Now you know the lingo, you’re probably ready to buy your first light. I have found a ton of inexpensive, used tungsten lights (Arri, Mole-Richardson, Lowel) on eBay. B&H also has a good variety of used lighting available on their website. However, I caution you to purchase extra bulbs as they often break if a light is shipped with the bulb installed. Wear clean gloves when handling bare bulbs and wipe them down with alcohol wipes (allowing the bulb to completely air dry) before use. Fingerprints will cause them to cease functioning and possibly explode. In closing, I would like to thank the GripTips YouTube channel for launching my interest in power.