What are ESC?

Let’s paint a picture of a pivotal component in an FPV drone with some descriptive turn of phrases. Strong and robust! Did your mind start shaping a blurred picture?? Herculean, powerful, indefatigable and very hardworking. BINGO, that’s absolutely right, yes, we are here to discourse about Electronic Speed Controllers(ESC).

ESC is the primary bridge, between the flight controller and the motor, that helps to connect them. The ESC makes the brushless motor spin by taking the signal from the flight controller while drawing power from the battery. You must have ran into the various applications of drones using brushless motors. These motors lack brushes or contact. Because they lack the brush, brushless motors use a different method to turn direct current (DC) into a variant of alternating current (AC). This is performed externally, with the use of an ESC.
There are a few fundamental types of ESCs out there. Most ESCs we find in the market are controlled by onboard 32-bit processors, running firmware called BLHeli_32 (pronounced B L Heli 32) or KISS.

image credits: getfpv

Lately, most ESCs were only using 8-bit processors, with only a few ESCs like KISS being 32-bit. 32-bit ESCs can articulate better with faster digital protocols, such as D-SHOT 1200. 32-bit ESCs are also have the ability to control light-emitting diodes (LED’s), change the direction of motor rotation such as by enabling features like the turtle mode (automatically righting a flipped drone with the motors). These ESCs are also capable of telemetry, whereby information from the ESC such as RPM, amp draw, and temperature are conveyed from the ESC to the flight controller.
Let’s throw some light on the two variant of the ESC hardware variant. In one of the two cases, ESC is treated as a single unit and is mounted on the arm of the drone between the flight controller and the motor. In the second case, a 4-in-1 ESC(all 4 ESCs are combined into one circuit board) is attached to the main stack under the flight controller. For lighter builds, or for a cleaner look, many pilots choose to purchase the 4-in-1 ESCs.
So, the ratings of the electronic speed controllers are based on the amount of current it is successful in conveying to the motors. The key task of the ESC is to switch on power to the motor coils at rates that are exceptionally fast. This switching is controlled by a microprocessor and carried out by transistors called MOSFETs, commonly referred to as FETs.
Amperage is the term that determines the current that conducts through the ESC and it is regulated by the size and quality of FETs. Most of the ESCs that you will come across will have either a rating of 30 amps or 25 amps, wherein such a number on the label determines the current sustained by ESC. Additionally, ESCs are also rated based on their ability to handle voltage. Some ESCs are rated for 3S-4S, while others can sustain up to 6S. The power of the motors can be computed in watts, which is calculated by simply multiplying voltage with amps.

image credit: bluerobotics

Consequently, as voltage escalates, amperage can drop to keep the total power output of the motor the same. This means that higher voltage batteries can provide the same motor output power at a lower current draw. On the other hand, when the voltage surges, and the pilot chooses to give a lot more throttle, the amperage will increase and the total power (watts) of the motor will increase and eventually the drone with a higher voltage will fly faster vs a drone with a lower voltage.
So how can an individual choose the most appropriate FPV Drone Electronic Speed Controller?? Well, to answer that, one must look out for 3 main components, because their perfect blend will eventually provide you with THE ONE FPV Drone Electronic Speed Controller you are in search of. The 3 considerations for ESC choice include motor size, propeller and battery.

image credits: robotics stack exchange

ESCs receive a throttle signal from the flight controller. Modern flight controllers and ESCs communicate with fast digital protocols, called D-Shot. An FPV Drone Electronic Speed Controller makes use of onboard microprocessors and hence require firmware to control the hardware. This firmware usually dictate which protocol your flight controller will utilize while communicating with your ESC. Depending on the type of ESC you have, there are currently a few types of firmware:
BLHeli: This is usually found on older 8-bit ESC’s. It is efficient enough to run oneshot protocols. The 8-bit microprocessor of later models, called the F390, masters faster analog signal Multishot.
BLHeli_S: This is also found on 8-bit ESC’s, but the hardware is more contemporary and is able to run all protocols (Oneshot, Multishot) up to D-Shot 600.
BLHeli_32: This is a new firmware which will run on the new 32-bit ESCs. It is capable of the faster iterations of D-Shot, like D-Shot 1200.
KISS: This is a proprietary ESC firmware that will only run on KISS ESCs. It is capable of Oneshot and D-Shot, and has features like telemetry and some other features.
This firmware can be upgraded by the users. Settings on the ESCs can be modified as per convenience using software that is available on both Macs and PCs. Here’s a pro tip, always prefer an ESC that can withstand greater amps and voltage as compared to the ones you intend to put into application. This is to make sure that there is enough room to catalyze growth in your journey while soaring the sky.

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