MOTOR SERIES: SENSORED VS SENSORLESS
If you are just getting in to the RC Hobby you will learn soon enough that there are many different motor options for use in your RC car. Brushed and brushless, sensored or sensorless, outrunner and inrunner to name a few. In this post we are going to talk about sensored vs. sensorless. Some background to start, in 2016 we released a brand new line of sensored motors after nearly a decade of sensorless only designs. Our design approach has always been to provide the most efficient motors in the industry, and after many months of developing our next-generation brushless motors, we incorporated sensors largely in part to enhance the crawling capabilities of our power packages. Some of the most common questions we answered during that time regarding our move to sensored vs. sensorless are shared below.
What makes a motor sensored?
Sensored motors have a small circuit board at the back of the motor with a small plug; there are also small sensors attached to the motor shaft. These sensors feed information back to the Electronic Speed Control (ESC) via a small 6-wire ribbon cable; this cable connects to the back of the motor and a port on the ESC. Sensored motors still utilize the three primary wires to provide voltage and current to the motor.
1406 Series Castle Motor (Exploded Parts View)
What are the differences between sensored and sensorless operation?
There are some operating distinctions between sensored and sensorless motors, each has its strengths and weaknesses. Our sensored design allows for users to combine the best of both worlds in an unrivaled HYBRID between smooth sensored startups and a high-efficiency sensorless drive. SMARTSENSE™ uses the motors sensors to start the motor to provide smooth starts, excellent torque, and low-speed drivability. Once the motor is turning, it seamlessly transitions to Castle’s ULTRA- EFFICIENT sensorless mode.
Sensored operation allows for a smoother initial start compared to a sensorless motor due to the detection of the rotor position The sensors allow the ESC to sense the rotor shaft’s position; this allows the ESC to start the motor at very low RPMs with no “cogging”. Sensorless motors will, by nature, “cog” or stutter when attempting to apply the throttle slowly from a complete stop.
Although sensorless brushless motors do not perform well at low speed, their performance at high speed is excellent. In place of using Hall-effect sensors for determining the rotor's position and/or speed, a phenomenon called back EMF is employed in a sensorless design. At high speed the ESC will alter the timing for the sequence of power pulses that are sent to the motor’s windings, in turn improving efficiency and performance.
The main drawback of sensored motors shows up at higher speeds when the sensor feedback becomes unreliable. Harsh conditions such as dusty or high-heat environments can affect the sensors and, therefore, motor operation. There are ways that a sensored motor can “monitor” its condition and we provide them within the industry leading software functionality of Castle Link.
When running, a motor must transition between different load points and a different timing advance is required for optimal efficiency at all load points. Using mechanical timing adjustments alone, you can only target one driving condition, such as higher start power or higher top end speed. This sacrifices performance and efficiency during the other driving phases. Electronic timing in SMARTSENSE™ will advance timing automatically for peak performance during all driving conditions.
Our new sensored motors are more serviceable compared to the sensorless versions. The motor wires are replaceable thanks to the large, high copper solder tabs. Replacement rotor shafts and front endbells with bearings are also available.
Can I run a sensored motor on a non-sensored ESC (IE Sidewinder 4 or Mamba Monster 2)?
Absolutely! But you will not be able to utilize the sensored capabilities of the motor. The ESC will simply run the motor sensorless; it will perform exactly the same as a non-sensored motor. Just connect the three primary motor wires and set aside the sensor cable that came with the motor. There is no disadvantage to running a sensored motor on a non-sensored ESC and you still have the serviceable advantages referenced on the previous question.
Do I install the motors the same way in my RC Car?
For sensored operation, the motor’s wires must connect to their corresponding letters on the ESC (A-B-C). (see diagram below)
Sensored vs. Sensorless Operation Setup
Are sensored motors waterproof or water resistant?
They are water resistant. We have added a double silicone conformal coating to the sensor circuit board to give it a level of water resistance. There are some precautions that need to be taken for reliable sensored operation and prolonged life. It is recommended to apply dielectric grease to the outside of the sensor port of the motor while the sensor wire is installed; if water gets in the sensor connection the motor will still operate, but it will operate in sensorless mode. Please refer the document “Running and Maintaining Castle Motors in Wet Conditions”
How do I change the direction of the motor when running sensored?
Unlike sensorless operation, you cannot simply swap two of the motor wires; the A,B,C wires between the motor and ESC must stay aligned correctly. To change the motor direction while running sensored you must change a setting on the ESC; the “Motor Direction” setting is accessible via the Castle Link USB programmer for Windows operating systems.
What Castle ESCs support sensored operation?
Currently the 1/14th/1:10th scale (crawler) Mamba Micro X2, 1/10th scale Mamba X, 1/10th scale Copperhead 10, 1/8th scale Mamba Monster X, 1/6th scale Mamba Monster X 8S and the 1/5th scale Mamba XLX2 are capable of sensored operation.
Can I trade in my old sensorless motor for a new sensored version?
Absolutely! You can take advantage of our trade-in program to get a reduced cost on a new motor with a new full 1-year warranty. You can find details on our trade-in program on our Service Center page.
Let us know in the comments below if you have any additional questions!