One Thing Every Lighting, Audio, and Video Tech Should Know in 2014

by Richard Cadena

If you’re a tech and you want to learn something new, try this. 

First, connect two or more computers to a network using a wireless router or network switch. Then go to the configuration page of the router or switch (open a browser page and go to www.routerlogin.net for Netgear routers or 192.168.1.1 for Linksys routers) and find the IP address and subnet mask settings. Change the subnet mask to 255.255.255.128. Then change the IP address on one of the connected computers to anything between 192.168.1.2 to 192.168.1.127 and change the other to anything between 192.168.1.130 to 192.168.1.254.

Now you should have two different subnets on the same network, neither of which can see each other. To test your two network, try pinging from one computer to the other by going into the Terminal app in Mac or Command Prompt in Windows, and type the command “ping” and the IP address of the other computer. If you have everything set up properly, then you should not be able to ping each other. But if you change the subnet mask to 255.255.255.0, then that will create a single network and you should be able to ping from one computer to the other.

Subnet masks allow you to subdivide network so that you can have, say, lighting and audio on the same network but separate from each other. They are also used to set up classes of networks, which determine the size of your network. There are three classes of networks; a class A network can over 16 million computers connected to it; a class B network can connect over 16,000 computers; and a class C network can connect up to 254 computers. Most of the networks we build in live event production are class C networks.

When a subnet mask is set up properly and it’s converted to binary numbers, it consists of a string of binary 1s followed by a string of binary 0s. For example, the subnet mask as written in the familiar quad-dotted decimal notation might look like 255.255.255.0, but in binary notation it is 11111111.11111111.11111111.00000000. 

The subnet mask also determines the class of network by designating which part of the IP address is common to the entire network, which is called the network portion, and which part is unique to each computer on the network, which is called the host portion. It does that by using a string of binary 1s to denote the network portion and a string of binary 0s to denote the host portion. Where ever there is a binary 1 in the subnet mask, that corresponds to the network portion and where ever there is a binary 0, it corresponds to the host portion. For example, if the subnet mask is 255.255.255.0, then the network portion of the IP address 192.168.1.24 is 192.169.1 and the host portion is 24. That means that every computer on the network has an IP address starting with 192.168.1 and ending in a unique number between 2 and 254.

The IP address is 32 bits long. If the network portion is only eight bits long, then the host portion is 24 bits, which allows 16,777,214 unique host addresses, and that’s a class A network. Class A networks are typically used by only very large organizations. If the network portion of the IP address is 16 bits long, then the host portion is 16 bits, which allows 16,382 unique host addresses, and that’s a class B network. If the network portion is 24 bits long, then the host portion is only eight bits, which allows 254 unique host addresses (there are really 256 unique numbers but one is reserved for broadcasting and one is reserved for the router or switch). That is a class C network, which is most commonly used for entertainment networks.

But here’s how we subdivide a network. If we add one or two more binary 1s to a class C subnet mask, then that allows us to subdivide it as we did at the beginning of this article. The subnet mask 255.255.255.128 translates to 11111111.11111111.11111111.100000000. Now it’s a class C network but the network portion is actually 25 bits long, not 24. That means that we can create a subnetwork with an IP address with a host portion in the range from 1 to 127 and another with a host portion in the range from 130 to 254.

This can come in handy if you want to minimize the wireless traffic because you are using only one router, and rather than having two routers competing for the same frequencies, now you only have one.

Computers and networks are becoming a much bigger part of the live event production industry and those techs who know how to set up, test, and troubleshoot them will have more options in the job market than those who don’t. So get some networking gear and go have some fun.

Greener Lighting for Greener Stages

by Richard Cadena

The typical 100-watt household incandescent lamp uses about a dollar’s worth of electricity to produce less than a nickel’s worth of light. The rest, about 97.4%, is radiated as infrared or pure heat, completely invisible to the human eye. Its overall luminous efficacy – the visible light output compared to the amount of power it takes – is about 17.5 lumens per watt compared to about 45 to 60 lumens per watt for a compact fluorescent lamp and slightly less for a typical LED profile luminaire. 

Coal Byproducts
About half of the world’s power plants are coal-fired, and they are the single largest source of carbon dioxide emissions on the planet. Some scientists believe that CO2 emission is the primary cause of global warming. Burning coal also releases other pollutants into the air. In addition to CO2, coal combustion byproducts include sulfur and many heavy metals like arsenic, barium, beryllium, cadmium, chromium, copper, lead, mercury, molybdenum, nickel, radium, selenium, vanadium, and zinc. The sulfur reacts with oxygen and water to produce sulfuric acid, which falls back to earth as acid rain, and the mercury released into the atmosphere is the single largest unregulated source of mercury. 

To power a 100-watt incandescent lamp from a coal-fired power plant an average of three hours per night every day for a year, which is approximately 1000 hours, it takes about 110 pounds of coal and produces about 200 pounds of CO2. If, instead, we replaced that 100-watt lamp with a 24-watt equivalent with a luminous efficacy of 50 lumens per watt, it would take about 26 pounds of coal to operate and it would produce about 48 pounds of CO2, a savings of about 84 pounds of coal and 152 pounds of CO2. 

But wait, there’s more…
In a closed system like a building or a room, all of the heat generated by a lamp has to be removed by the air conditioning system if the temperature is to remain the same. Doing so requires the use of even more electricity. 

For example, a 100-watt lamp gives off 341 British thermal units (BTUs) for each hour of use, which increases the heat load by the same. The impact of that heat and the amount of air conditioning needed to remove it depends on the efficiency of the air conditioner. An air conditioner with a seasonal energy efficiency ratio (SEER) of 7.5 will use 34.1 watt-hours of energy to remove that heat. In effect, it increases the energy consumption of this lamp by 34%, adding to the cost, CO2 emissions, and pollution.

Efficiency Pays
A church in Houston was originally built in the early 1970s and the lighting was upgraded in the mid-1980s. It had three stained glass windows that were backlit with 190 1000-watt cyc lights and there were 168 1000-watt PARs used for the house lights. By replacing cyc lights with 109 324-watt T5 fluourescent fixtures and the house lights with 575-watt ERS fixtures, the energy consumption was cut by 55%. In addition, the lower power consumption results in a lower air conditioning load, saving even more energy and money. With a conservative estimate of 20 hours per week of use, an electrical cost of $0.0986 per kilowatt-hour, and a SEER of 10, in a year’s time, the building owner will save about $28,600.

Before:

Total energy consumed: 392,080 kW-hours

Total thermal load: 1,286,377 BTUs

Annual cost of electricity for A/C: $13,191

Annual cost of electricity for lights: $38,659

After:

Total energy consumed: 175,848 kW-hours

Total thermal load: 576,942 BTUs

Annual cost of electricity for A/C: $7,275

Annual cost of electricity for lights: $21,320

Total Annual Savings: $28,595

Amount of coal saved annually: 119 tons

Amount of carbon dioxide saved annually: 218 tons

Coal-burning power plants also release arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, molybdenum, radium, selenium, vanadium, and zinc into the atmosphere. Saving energy not only saves money, it also makes good environmental sense.