Choosing the right Electronic Speed Controller (ESC) for your radio control electric aircraft can be made quite simple. ESCs are available with many different features, limits, and price ranges. Sorting through the list of ESCs can be done by identifying what you need, and eliminating the rest.
The general procedure is to narrow the list down to ESCs that will get the job done, and then make your final selection based on price and preference. First, select ESCs based on their most fundamental features.
Brushed or Brushless?
R/C speed controllers are separated by the type of motor they work with, either brushed or brushless. If your motor has two wires, it is brushed, and you need a brushed speed control. If it has three wires, it is brushless motor, and you require a brushless speed control. An exception to these rules are ESCs that can work with both types of motor, however this feature is not commonly available. Castle Creations and Hacker Brushless are two manufacturers of brushless motors and ESCs.
An ESC will have a power limit. To handle more power, the ESC needs to be larger, heavier, and is more expensive. It’s important to know the peak current your motor is going to pull at full throttle. This determines the current rating you should look for in an ESC. Always choose an ESC with a current rating that is higher than what you need. If the motor is going to pull 12A, a 25A-rated ESC is a much better choice than a 10A-rated one. The 10A ESC will probably overheat and cook, even if you only fly at half throttle. ESCs are relatively light and maintain great resale value, so this is one item in your power system where skimping isn’t worth while.
Choosing the correct type and identifying the minimum current rating are the two big steps. The next choices depend on your preferences. Here are some of the features and limits that can affect your selection.
All ESCs have voltage limits. Some even have more than one! What is your battery voltage? Choose an ESC that is designed to work with an equal or higher voltage. Some ESCs are designed for low voltages (below 13V), some for medium voltages (below 25V), and some for high voltages (above 25V). You shouldn’t connect a high voltage battery to a low voltage ESC, but it is also wasteful to use a high voltage ESC with a low voltage battery. The second voltage rating that some ESCs have is based on their Battery Eliminator Circuit (BEC). For an ESC to provide power to your receiver and servos, it has to drop battery voltage down to 5V. This becomes difficult once battery voltage is above 13V, so usually a separate receiver battery or voltage regulator is required. Consider what is going to be powering your receiver and servos.
Low Voltage Cutoff (LVC)
To protect your lithium polymer battery pack from being discharged too much, most ESCs can shut down when they sense battery voltage has become too low. This is almost always a useful feature, as it can save your li poly battery from being permanently damaged.
ESCs with the same current and voltage rating can vary in price. Investigate this large market, and put prices on the features that you want.
Some ESCs simply work out of the bag, like a servo. Others can be fine-tuned and set up with exotic throttle profiles. The most advanced can be configured via a computer program and cable.
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