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Batteries and Charging: The first thing you have to do after unpacking your new RC system is charge the batteries that power the system. I wrote about this last month. RC transmitters are usually powered by eight AA-size battery cells, and the typical airborne pack (the pack that goes inside the model) has four cells (usually AA, but they can be smaller). In some of the inexpensive and basic systems, you may have to use nonrechargeable alkaline battery cells. If you do, purchase at least a dozen cells and insert them into the transmitter and receiver battery boxes. Be careful to observe the battery polarity (positive [+] and negative [—]). Most RC systems will be provided with rechargeable batteries. The majority will be the Nickel Cadmium (Ni-Cd) variety. To a lesser degree, you may be supplied with Nickel Metal Hydride (NiMH) batteries. As a beginner you won’t have to be concerned with the type of battery because the manufacturer will have thoughtfully provided the correct companion battery charger. That charger will usually be a wall-plug type transformer with two cables exiting the case (small black box). The transformer plugs into any 115VAC electrical outlet. One cable exiting the transformer gets plugged into the charging jack located on the side, bottom, front, or rear of the transmitter case. The connectors for the transmitter and receiver are different, so there will never be any confusion about which cable goes where. On the receiver side there are two possibilities for charging your batteries. In one case you physically unplug the battery pack from the switch harness and plug the charger cable directly into the battery. On some of the more deluxe RC systems, the switch harness includes a charging jack. When this is provided, you don’t have to unplug the battery pack. Just plug the cable into the charging jack, which is an integral part of the switch-harness assembly. But to do this will normally require that you remove the wing so you have access to that cable, which is located inside the fuselage radio compartment. Some manufacturers make these charging jacks so they can be mounted on the side of the model’s fuselage, such that they protrude to the outside. With that kind of arrangement you can plug in the charger cable from the exterior of the fuselage without the need to gain access to the radio compartment inside the aircraft. Almost all charging will be done at home in your shop, and presumably the wing will have been removed for transportation and storage purposes. The external fuselage charging jack will come into play later, when you learn to use field-type battery-capacity testers or when the need arises for a quick field charge. It is important for you to determine that your charger is working properly before you leave it unattended. Each wall-plug transformer will have two colored light-emitting diodes (LEDs); they may be red, green, or red and green! When you successfully connect a charger cable, that LED should glow to let you know that the charging has started. If you are charging both batteries, you should have two glowing LEDs. The first time you charge your new battery packs, you are advised to leave them on charge for a full 24 hours. After that, it is normal to leave the charger on overnight. These batteries have been designed to take hundreds and hundreds of recharging cycles. Most batteries will provide several years of regular service without degrading in performance. Because your RC-system charger operates on such a low level, nothing will really happen if you forget and leave a charger on for, say, 48 hours. In the same regard, don’t play the “I’ll put back in what I took out” game; that is, you use the RC system for two hours, so you recharge it for only two hours. Don’t even think of doing that! The battery chemistry is such that it must be on charge for a period of at least 10 hours each time. If you plan on flying the next day, put the charger on the night before. If you don’t fly the next day because of bad weather and a week goes by, charge it again. When in doubt, charge again; it can’t hurt, but it sure can help! One final caution: when charging, make sure you plug your charger into a 115VAC outlet that remains on all the time. Let’s say you choose an outlet that is operated by a switch near the door to your shop. As you exit the shop for the night and turn off the overhead lights, you may have also turned off your charger. The next day you go flying and your model crashes after the first or second flight because the batteries were never charged. The subject of batteries is extremely important to the RC system’s operation. As I progress in this series I will feed you more information about battery-capacity testing at home and at the flying field. Connectors and Wiring Polarity: Your RC transmitter is a self-contained unit that you hold in your hands. On the aircraft side you have a series of components that must be installed or mounted inside the aircraft fuselage, then all of those components must be connected so you have an operating airborne RC system. That interconnecting is done with “connectors.” They allow you to make and break electrical connections without needing to solder wire; the manufacturer has already done the soldering and/or mechanical wire crimping for you. Years ago, types of connectors varied considerably from manufacturer to manufacturer. One brand would not work with or fit into another brand. In many cases the wire color coding was different, as was the order of polarity. Things have become more standardized throughout the industry, but the best advice I can give you when starting out is never mix or match different brands of connectors. If you purchased a Futaba RC system, use only Futaba components and Futaba connectors. The same goes for the charger and charging cables I just discussed. Use only the charger that was supplied with your system. For now, while you are getting started, use the components as supplied. You may make exceptions to this rule as you gain experience. Most connectors have keyways or slots that permit them to be connected only one way. Wiring convention used by most of the RC industry today has the positive (+) pin or wire in the center of a basic three-pin connector. Battery power circuits use two wires, and the servo cables have three wires. By having the positive wire in the center, if you are actually able to plug a connector in backward, the circuit will be incomplete. Nothing would work, but at least nothing would be short-circuited and blow out. Click on photo to view large image with caption |
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