Keep Communication Equipment Powered in an Emergency, Part 1

There's no doubt that high-tech communications equipment is increasingly playing a vital role in disaster relief efforts. In the aftermath of Hurricane Katrina, displaced residents from New Orleans and other affected regions relied on ad-hoc Internet kiosks to connect with loved ones and find housing outside the disaster zone, while relief workers used cell phone calls, SMS messages, and e-mails to coordinate efforts.

But keeping all that equipment powered up in the midst of a crisis, when the electric power grid is likely to fail, is no easy task. Even organizations that have uninterrupted power supplies ( UPSs) and backup generators can find themselves in a bind when the lights go out. After all, UPSs only keep equipment powered long enough to get past brief power outages, and gas-powered generators have their own issues, like noise and ventilation requirements.

One option is to supplement backup solutions like these with an emergency power kit. At the least, the kit should contain basic electrical doodads, like cables and batteries, that are so hard to find once a disaster actually strikes. Depending on how critical communications equipment is to your organization's mission, you may also want to stock your kit with enough electrical components so that, in a dire situation, you could splice together a connection between just about any battery and the power input jack on your router, Wi-Fi base station, or other communications device.

Preparing an Emergency Power Kit

Since different organizations will have different needs, we've separated the emergency power kit into two sections: must-have supplies, and advanced supplies. The must-haves should help you cope with most power outages. The advanced supplies are handy for situations in which your power sources are limited yet you absolutely have to get some critical device powered up. In the second part to this series, I'll show you how to use the advanced supplies to connect just about any battery to any communications device.

Checklist:

Must-Have Supplies

Advanced Supplies

Must-Have Supplies

The supplies on this list should make most power outages easier to deal with.

Specialty batteries.

Most people remember to stock up on standard batteries for emergency flashlights and radios, but it's important not to forget the specialty batteries that fit into your organization's cell phones, laptops, and other devices. These batteries are hard to recharge or replace in the midst of emergencies.

Don't forget that batteries lose charge over time. If you get advance warning of a disaster, such as an oncoming hurricane, it's a good idea to make sure your specialty batteries are fully charged.

High-power batteries.

The standard A-, C-, or D-cell batteries you put in your flashlight don't have a lot of power. So if you think you're going to need to keep a lot of communications devices running for hours on end without the help of a gas-powered generator, it's a good idea to keep some lead-acid batteries with your kit.

The lead-acid battery that most people are familiar with and have easy access to is the standard 12V car battery. These are designed to provide a lot of power in short spurts, mainly to start a car engine. They're good if it's all you have access to, but they may not survive if you keep using them up and recharging them multiple times.

A better option is to get a deep-cycle battery, which is designed to provide a steady current over a long period of time.

Specialty chargers.

If you're lucky, you may get a chance to recharge your specialty batteries by plugging a charger into a gas-powered generator or into an electrical outlet that's connected to a working section of the electrical power grid. Don't miss out when an opportunity like this pops up: have your specialty chargers ready.

Also, check whether you can get specialty chargers that plug into the cigarette lighter socket in an automobile. These are definitely available for cell phones and will make charging up very easy.

Cables.

If you do get access to a gas-powered generator during an emergency, it may be set up outside for ventilation purposes. Extension cords will let you power your equipment where you need it most.

Don't forget other networking cables, too. In an emergency, you may have to reconfigure networks on the fly. Stock extra Ethernet patch cables, a spool of CAT5e, RJ45 connectors, and the tool for affixing them. Also, don't forget a separate Ethernet crossover cable which you might need to connect a laptop directly to the network equipment if the equipment has no MDI/ MDI-X autosensing feature. (It's best not to count on it).

Finally, note that CAT5 cable is especially handy. When you connect two pairs together, it can be used as a short-haul power cable for the battery. (But you can't use it for too long of a distance and too high of a current, though, as the wires are rather thin and you would lose voltage on their resistance). You can also use it as a telephone cable, for audio signal. Or you could pull the individual wires from it and use them as short patching wires or even to tie things together.

Power inverter.

When the electrical grid goes offline, an inverter provides the easiest way to power up devices that don't normally use batteries, like Wi-Fi base stations and routers. The inverter is a device that plugs into a car battery on one side and has a standard electrical plug on the other side.You can this plug to connect and power any device with a low enough power rating. (Using an inverter, you could run a 110 V-powered TV from a car battery.)

Laptop computer.

Once you get, say, a Wi-Fi base station powered up, you'll want to connect to it with a laptop to configure the station's settings and prepare it for use. You can usually do this with an Ethernet cable, though having a Wi-Fi card in the laptop may be more convenient for configuring multiple devices.

You will also want to pre-load the laptop with network analyzing software (like tcpdump or ethereal) and Wi-Fi analyzer software (like Kismet or Netstumbler) to be able to see what devices are nearby, what devices talk with which ones, and what channels are available to claim. Get some experience with these tools before an emergency happens. The ability to see network activity is essential for finding flaws quickly.

Manuals.

Unless the configuration interfaces for your devices are incredibly intuitive, you're going to need the manuals for those devices. The manuals should contain the default passwords for the devices so you can access them once they've been reset.

It is also strongly advisable to write important information, like the access passwords and MAC addresses, in the manuals or on the devices themselves. This goes against the spirit of access control in a conventional setting, however in a crisis it is more important to have immediate access instead of losing valuable time. Less permanent information like the configured IP addresses can be written on post-it notes or a piece of tape attached to the given device or manual.

Keep in mind that some wireless access points have two MACs, one for the wireless side and one for the Ethernet side. Write both addresses on the cases.

A somewhat compromised option for equipment used both in crises and in "peacetime" is to write the more sensitive information on the inner side of the equipment cases, depending on the tradeoff between need for security and the need for quick access when disaster strikes.

Alternate communications devices.

As you rush to put together a Wi-Fi base station or some other high-tech communications device, you'll need some means for your team to stay in touch. This may range from two cans and a string -- which I used between two buildings as an ad-hoc intercom and which can be surprisingly practical where the geometry of the situation allows it -- to satellite phones, depending on your teams preferences, budget, and goals.

Small handheld transceivers are a practical solution, but depend on batteries. Low-tech options include: using Morse code with a whistle, sign language with optional binoculars, or any variant of flag signaling. (Former Boy Scouts should have an advantage here.)

Standard tool set.

You want to make sure you've got the tools to disassemble and reassemble all the equipment you have on site. That includes combination pliers, wire cutters, and screwdrivers. You never know when you will have to get inside something. If your equipment uses screws with non-standard heads, replacing them with the standardized flat screws or Philips ones is strongly advised. Do not forget a screwdriver with a long thin shaft, which can reach screws "conveniently" located in obscure distant parts of the equipment; such a surprise can ruin your day otherwise.

Duct tape.

Duct tape holds the world together. It can be handy for putting covers back on devices without screws, or for labeling equipment, among other things. Don't underestimate the amount you'll need, as you can have too little but never too much.

Colored electrical PVC tape can be handy, too, to quickly and easily distinguish which cables belong to which devices. This also allows for easy directives for your crew, along the lines that red-marked devices are mission critical while green-marked ones are fair game and can be cannibalized to keep the red ones running.

Permanent markers.

Human memory tends to be imperfect, especially under stress and fatigue, and it's not advisable to assume the rest of your team knows exactly what you are doing. If you can mark cables, devices, and other items with notes and instructions, you've got a better chance of running a successful operation.

Advanced Supplies

In an emergency where you can't plug the standard power adapters that come with the devices into the electrical power grid, you may have to improvise by splicing together electrical components to create your own custom adapter that draws power from a battery.

Most of these electrical components on this list are available at your local electronics supply store, like Fry's or Radio Shack. Though you don't have to know exactly how each component works, we highly recommend that you familiarize yourself with the following components and circuits in "peace time" so that you're more efficient at using them during an emergency.

Power connectors.

If you have to build a custom power adapter that draws its juice from a battery, you'll need to have on hand spare plugs that fit the power input jacks on your various communications devices. These plugs are usually cylindrical-style DC connectors. You can buy them separately, or in sets with some universal power adapters that you get at your local electronics supply store.

Make sure in advance that your connectors match your devices. The polarity of the connector is usually indicated on the box. However, when in doubt, the outer rim of the cylindrical connector is usually connected with the negative terminal of the power connector while the inside prong is the "hot" terminal.

In a pinch, you could simply cut the connector and a little bit of wire off the original power adaptor. Just keep in mind that this might make it difficult to revert to using the electrical grid once electricity has been restored.

Battery clamps.

You'll need something to connect the wires in your circuit to the batteries that you're using. There are different options for different batteries. For instance, car batteries will need spring-laden clamps, while other lead-acid batteries usually require "fast-on" connectors.

Voltage regulators.

These little components help reduce and stabilize the voltage coming in from a battery to a level that's suitable for your communications device. They can be bought for just a few dollars at most in stores that sell electronic parts, like Fry's.

It's a good idea to pick up some 78S05 and 78T05 regulators, which are 5V stabilizers in 2- and 3-ampere versions. You may also want a 78S09 chip if you expect you could need to power a 9V device. These generally come in 2-ampere versions.

You may also want to get some 78S12 regulators for your 12V equipment. Keep in mind, though, that this regulator may "lose" some Volts and output less than the number of Volts that you put into it. In other words, you might need a 14V battery to power 12V equipment with this regulator.

Capacitors.

These cheap components keep the current flowing to your equipment at a steady rate despite sudden spikes in demand for electricity. Pairs of 100 nanofarad ceramic capacitors and 100 microfarad electrolytic capacitors will usually do the job and usually cost well under $1.

Note that you have to be careful about voltage rating of the capacitors. The rating always has to be at least slightly higher than the highest voltage present on that part of the circuit. In other words, you can use 6.3V capacitors for the 5V output side, but you have to use at least 15V capacitors for the battery side. The price differences for the capacities we need are quite low though, so you can't go wrong just getting capacitors with a 35V capacity.

Heatsinks.

When you use a voltage regulator to reduce the input from a 12V battery to just 5V, the regulator turns those extra Volts into heat. This could make regulator scalding-hot and maybe even lead to its self destruction.

The regulators should have their own thermal protection, but testimonials suggest it's best not to rely on this protection alone. To assure that things stay cool, attach a heat sink to your regulator. The smallest ones can be cannibalized from a dead computer power supply, however heat sinks from computer CPUs are bigger and significantly better.

You'll probably want to mount your regulator on the heat sink by drilling a hole in the heat sink and putting an M3 bolt through it. Preferably, this would be done ahead of time so you're not trying to find a working cordless drill in an emergency. Also, putting some thermal grease between the heat sink and the regulator case is strongly advised.

Ressettable fuses.

Because ad-hoc installations done in adverse conditions by technicians in dire need of sleep are prone to wiring mishaps, a strategically placed fuse can turn a smoky sparkly accident into an unimportant event. Resettable fuses have the added advantage that they become conductive again shortly after the circuit is disconnected, therefore you do not need to have a supply of spares, like you'd need with classical glass cartridge instrument fuses. Get some resettable fuses that are rated to handle 0.5, 1, 1.5, and 2.5 amperes of current.

Transils.

When using power generated from a running car or from a gas-powered generator, there may be voltage spikes present in the feed. (The same is true if you connect anything that contains coils, like electromagnets or motors, to a battery you're using to power your equipment.) Transils clip this excess voltage so it doesn't reach -- and ruin -- more sensitive equipment. Transils come in two variants: bidirectional, and unidirectional. Use the unidirectional ones; they behave as Zener diodes, not allowing any current to go through until a threshold voltage is reached in the "right" direction. This means that if you accidentally swap the polarity of the battery, the transil will act as a short circuit and trigger the fuse. A Zener diode could be used too, but transils are specifically designed to absorb voltage spikes, so they're more suitable for this purpose.

Diodes.

Like transils, diodes can protect your equipment when you accidentally switch the polarity of the power supply -- which is surprisingly easy under field conditions. Also, there's a little voltage loss across a diode, which can be exploited for fine adjustments of the voltage needed for your communications equipment. (For instance, you could use a stabilized 5V power source and three diodes in series to make a 3V output -- perfect for a device that otherwise runs from two 1.5V AA cells.)

LED diodes.

LED lights are very handy as power indicators, showing that a device or cable is powered. Be sure to get some resistors to put in the circuit next to your lights so you can minimize the power the lights consume. The lights will be dimmer, but every milliamp you save counts.

Get as high a resistor as the LED allows. A rule of thumb is that normal LEDs need 10 milliamps, while low-power ones are happy with 1 mA. Take a random sample of red and green ones, but remember that there's a voltage loss of 1.5V on red and 2V for green, which can be used for adjusting the output of the 7805 regulators.

Multimeter.

When you're putting your circuit together, you'll be able to troubleshoot problems quickly if you can measure the voltage and resistance across different parts of the circuit using a multimeter. The meter doesn't have to have laboratory-grade accuracy, but should be reliable and abuse-tolerant. You may also want it to have an audible indicator of a short circuit -- it's much more comfortable than having to stare at the display.

Voltmeters.

Though you'll have your multimeter, the difference of being able to glance quickly at a voltmeter versus having to mess with a multimeter can be significant when you're under stress. If you can, get the inexpensive analog voltmeters that do not need batteries to work. If you have one for every device you adapt, you can wire it to the battery as a direct-read battery status indicator.

Propane torch, with soldering tip.

You won't have power from the electrical grid, so your electric soldering iron will be of little use when it comes time to assemble your custom power adapter. A propane torch will allow you to improvise wildly. Just remember that you'll also need rosin and tin, and probably a spare can of propane.

Hot glue sticks.

The glue sticks used for hot glue gun applications are made of a useful material that can be used, not only to bond things, but also to seal and insulate parts and joints. The low melting point of the sticks means they can be melted by a candle flame, a lighter, or a propane torch.

Keep Your Kit Close at Hand

Whether you stock the must-have supplies in your kit or you double-up on everything on the list, be sure to store your kit near your other emergency supplies so that you can access it easily when you need it. Disaster situations that knock the power grid offline are difficult no matter what; but with a little planning and a bit of ingenuity, you can make sure you keep the lights on and the network up.

Check back soon for part two of this series, in which I'll take you through the steps of using the advanced supplies to build ad-hoc power adapters that keeps your communications up and running in the direst of situations.