Selecting ESCs for Your Multirotor
After selecting props and motors, you are probably a bit tired of making complex and important design decisions. Well good news, choosing an ESC is easy. Before we get to the easy part though, I just want to take a moment to explain what an ESC is.
What is an ESC?
ESC stands for Electronic Speed Controller. In the Selecting Motors tutorial, we discussed that one of the differences between brushed motors and brushless motors is that brushless motors require control circuitry. ESCs are controllers for brushless motors. They control the flow of electricity into the electromagnetic coils inside the motor in such a way that the motor shaft is made to turn. ESCs are used to control the rotational speed of brushless motors.
Now for choosing an ESC. When shopping for ESCs, you should easily be able to find the maximum current rating for the ESC. To figure out what maximum current rating you require, look back at the documentation for your motors. You should be able to find the maximum current draw of the motors. Always choose an ESC with a maximum current rating higher than the maximum current draw of the motor. The ESC’s current rating does not have to be too much higher though, because the higher the ESC’s current rating, the heavier and more expensive the ESC will be. For example, if your motors have a maximum current draw of 15 amps, choose ESCs with current ratings of about 20 amps.
Opto vs. BEC ESCs
There is one more little complication though when choosing ESCs. ESCs are available in two different types: Opto, and BEC. The performance of these two types of ESCs is actually exactly the same with respect to how they communicate with the motors. The difference between Opto and BEC ESCs is how they deliver power to the rest of the multirotor’s systems. The difference between Opto and BEC ESCs is a complex enough issue though that I decided to create a separate to cover the decision. If you want to just make your decision easy, go with a BEC ESC.