SpringdaleHighschool

My name is Jake and i am on a team for Springdale High School where we must build a combat robot. We recently purchased an E-Flite Power 32 Brushless Outrunner motor to power our weapon. We were wondering if we needed a speed controller to run this brushless motor. We originally planned on using a relay to switch the power to the motor on and off, but if we need a speed controller that would greatly affect our design. Any help will be greatly appreciated. Thank you. Jake.

Jim Schwagle

My Feedback: (1)

Yup. You can't just feed it power like a brushed motor connected to a battery, to the best of my knowledge. Sorry.

The robots our kids build have motor(s), speed controller(s), servo(s), receiver and battery(ies). The transmitter sends signals to the receiver which passes them on to the speed controller if necessary, which acts like a throttle for the motor. Servos control arm movements, picking things up, steering, etc. Brushless motors require speed controllers, you can't just turn them on and off by supplying voltage through a switch.

SpringdaleHighschool

Thanks, any suggestion on which ESC to use?Also, ive been looking up some 60A ESC's and ive seen they have a switch mode option. What is switch mode? Would that work for my situation to just have an on off controlled by the receiver? If not, how do you suggest i connect everything?

Jim Schwagle

My Feedback: (1)

The speed controller is connected to the motor, a battery and the receiver (which means you need a transmitter too). I would recommend visiting a local hobby shop, they can help you with the speed controller. Brushless controllers are somewhat generic and most will work. You choose the controller based on how much current you intend to put through the motor. The motor should have instructions that come with it that will help you choose. The hobby shop can help you select a battery and charger appropriate for how it's going to be used. I'm not sure what they meant by "switch mode". Many speed controllers can be programmed with many settings and this may refer to one of them. Do google searches on robots and I'm sure you'll get many hits.

RCUniverse also has a robot forum where I'm sure more knowledgeable people can directly help you. This is probably the next place you should go.

Good Luck...

Edit for grammar, duh!

jdetray

Hi Jake -

Switch mode refers to the type of battery eliminator circuit (BEC) that is built into the speed controller. The BEC is a feature that allows the main battery for the motor to also supply power for the receiver and servos. In an airplane, where weight is extremely important, the BEC eliminates the need for a separate battery for the receiver and servos. Such weight savings is probably not so important for a robot, so you could afford the weight of a battery for the receiver and servos.

The BEC is really just a voltage regulator that reduces the voltage of the main battery down to the 5-6 volts required by the receiver and servos. A "switch mode" BEC is more efficient and can handle more current than the "linear mode" BEC used in most speed controllers.

- Jeff

Walt Thyng

My Feedback: (9)

There is a lot of useful information in the above posts, but perhaps a key point was missed or presumed to be understood. The difference between a brushed and a brushless motor is in the "commutation" or process by which the motor is made to turn. In a brushed motor commutation is accomplished through carbon brushes (thus the name). In a brushless motor commutation is done electronically in the speed controller (again, thus the name). Power reaches the motor through the commutation process, therefore it needs to be applied at a point where this can occur. That is why you can apply power directly to a brushed motor, but it must go through the esc on a brushless motor.

I'm sure that the technical types who read this will have some problems with my language, but I'm trying to help you with your project, not make you an electrical engineer or physicist (-:

By the way, a little hint: if your motor turns the wrong way just switch any two of the wires between the motor and the esc. Like most things electrical there is another way to reverse motor rotation: the majority of escs will let you do it through their programming, but switching wires is usually quicker and easier.

Hope all of this is a positive learning experience for you,
Dr. Walter I. Thyng