Support Center - FAQ - Electronics

Where is the instruction manual for my Electronic Speed Controller (ESC)?

  • ESC setup instructions can be found on each product page under the Manualstab. Click on the UAS ESC Series Instruction Manual (PDF) link to view the most recent information and safe-operation requirements. The manual is provided as a guide through your ESC set, and it is critical that you read through the full manual and follow all instructions before operating the ESC.

How do I update my ESC to the latest Firmware?

  • To update your ESC to the latest firmware you will need to download the KDE Device Manager.
    For KDE UVC series ESCs: The KDE Device Manager can be found under the KDE-DMS page.
    For all other ESCs: You will need the KDEXF-DMA Device Manager Adapter.

Are the firmware updates free?

  • Yes, KDE Direct is a Research and Development company, that continually strives to improve technology and functionality in the UAS industry.

How do I connect my ESC to program it (DMA)?

  • The KDE UVC series ESCs don't require an adapter. Simply plug your ESC into your computer with the USB cable provided with your ESC. For all other ESCs, you will need the KDEXF-DMA Device Manager Adapter
    When programming an ESC with the DMA, make sure that the adapter is connected to the programming cable (Orange, Red, Brown) in the correct orientation as shown below.

    You can verify that the ESC is properly connected to your computer by starting the KDE Direct Device Manager. Once the device is recognized, the device status will turn green.

Do I need to calibrate my ESC?

  • If you are using a DJI flight controller then throttle calibration is not required. For alternate flight controllers such as Pixhawk, we recommend using a UBEC and setting the min and max on the ESC to the same min and max on the flight controller. Our setup guide can be found here. For more information see Understanding Throttle Calibration and Deadbands.

How do I calibrate my ESC to set the minimum and maximum throttle?

  • The throttle calibration mode can be changed by connecting the ESC to the KDE Device Manager PC software. The default throttle calibration mode is DYNAMIC and utilizes an auto-scaling algorithm which dynamically adjusts throttle endpoints based on input. The throttle calibration mode MANUAL can be used to manually calibrate the ESC with an RC radio. When the throttle calibration mode is set to RANGE the ESC will use the min(low) and max(high) PWM endpoints. The following throttle endpoints will then be used:

    Motor Arming Throttle: 0%
    Motor Stopping Throttle: 2%
    Motor Spinning Throttle: 3%
    Max Thrust: 97%
    Full Stick: 100%

    0%                                                                                                 100%
    | brake_zone  |                | spin   |        throttle_zone         |       |
    | min                | brake     |            | motor on                       |       | full stick
    |                                         | motor stop                                | motor max

What are the different ESC features by series?

  • KDE UAS Series ESC (2S to 8S systems)
    - Anti-spark circuitry
    - Bidirectional Opto-Isolation
    - Synchronous Rectification
    - Regenerative Braking
    - Adjustable Drive Frequency Resolution
    - Dynamic Timing and Start Power
    - Synchronized Motor Commutation
    - Stall Protection
    - Temperature Protection
    - Over Voltage Protection

    KDE HVC Series ESC (3S to 12S systems)
    - All UAS Series Features
    - Thermal 6061 Aluminum Casing
    - Overload Protection

    KDE UVC Series ESC (4S to 14S systems)
    - All HVC Series Features
    - KDECAN bus with Live Telemetry
    - Data Logging
    - Micro/Mini USB port
    - Under Voltage Protection

What is the second lead (orange/red/brown wires) on the KDE Direct UAS ESCs used for?

  • There are two leads included on the XF and HVC series ESCs: (1) the control line from the ESC to the flight-controller or direct-receiver (white/red/black wires) and (2) the dedicated programming line to the ESC (orange/red/brown wires) using the Device Manager Adapter Programming Kit (KDEXF-DMA).
    The dedicated programming line allows for updating and programming the ESC without needing to disconnect any leads. Please review the latest Instruction Manual included with the ESC or found online for full details on proper installation and connection.

For FPV Racing, what is the weight of the KDEXF-UAS20LV ESC with the heat-shrink and heat-sink removed?

  • For clients looking for the ultimate performance in FPV Racing, the KDEXF-UAS20LV ESC can be reduced in weight by removing the heat-shrink cover and heat-sink. This will reduce the maximum continuous amperage capability of the ESC from 20A to 12A (up to 6S voltages), but the overall weight becomes a mere 7.0 grams!

How much heat do ESCs produce during normal flight use and can KDE products be in enclosed spaces?

  • Due to the physics and material characteristics in BLDC control, the ESCs produce heat that needs to be transferred to a heat sink that can either be the atmosphere or a metal plate. If the ESC is fully enclosed without a heat sink, the performance output of the ESC will be limited and the lifespan may be shortened. To reach the full performance capabilities, the ESC should be exposed to a minimum 5 mph airflow. The motors have a centrifugal fan design in the rotor. This fan pulls air down into the stator core and over the coils. This airflow allows the coils to maintain safe operating temperatures, and designs that limit this airflow should be avoided or the power of the motor should be limited to avoid damaging the motor.

What is regenerative braking and what does it have to do with synchronous rectification / active freewheeling?

  • The standard braking method with ESCs is called passive-current freewheeling. In this method, the conversion of mechanical power to electrical power during braking is burned off as heat within the ESC. KDE Direct ESCs are optimized to use active-current freewheeling. Rather than having this power converted into heat, the power is recycled back into the batteries (known as active-current freewheeling). The MOSFETS allow the circling AC currents to pass back through the ESC as DC power that recharges the LiPo batteries during operation. Overall the increase in efficiency is ~10% for the overall flight when S.R. braking activation is enabled. You can enable S.R. braking activation using the KDE Device Manager PC software.

My ESC has anti-spark technology, what does that mean?

  • ESCs without anti-spark protection will produce a spark when their leads come in contact with a battery’s leads. This spark can be a potential fire hazard and can damage the internal circuitry with a large current shoot through. Anti-spark protection eliminates the spark and current shoot through when connecting to batteries.

What is Stall Protection?

  • Stall protection is a safety feature that can be enabled through the KDE Device Manager. Stall protection will detect if a propeller has been blocked or frozen in place and prevent the ESC from continually trying to spin the motor.

What are the optimal ESC settings for flying in inclement weather e.g. high winds? Would there be drawbacks in mild conditions?

  • If you are expecting to fly in windy conditions, you can change the acceleration rate of the ESCs to HIGH or ULTRA-HIGH in the KDE Device Manager. A higher acceleration rate will enable the ESC and motors to respond faster to throttle changes. This may increase the stability of the system at the expense of higher amperage draws and potentially higher operating temperatures.

Are KDE Direct ESCs opto-isolated?

  • Yes. This means that the power to the ESC via the control lead is isolated from the battery leads and the signal is transferred via light (phototransistor). Depending on your flight controller, you may need a UBEC to supply voltage (3V to 12V) to the control lead (white, red, black wire).

Do I need to use a UBEC?

What is a UBEC?

  • A UBEC (universal battery elimination circuit) reduces the input voltage to a lower level and outputs constant voltage. There are two types of battery eliminator circuits, linear and switching. Linear BECs burn off excess voltage through resistors as heat. Switching BECs (UBECs) produce voltage that does not waste power through heat.

What is the purpose of using a UBEC with a KDE Direct ESC?

  • The purpose of the UBEC is to supply power to the control lead (white, red, black wire). A UBEC is only needed if your flight controller does not supply power to the control lead.

How much voltage does the control lead need?

  • 3V to 12V. If this voltage is not supplied then the PWM throttle signal won't be amplified. The PWM circuit contains a NPN transistor for amplification and a phototransistor for optical isolation.

How much current does the red control lead wire draw?

  • ~60-70mA.

Can I supply the 3V to 12V power to the control lead without using a UBEC?

  • Yes, we recommend using a UBEC but any regulated voltage source will work.

Can I put my UBEC in parallel or in series with another UBEC?

  • No.

What is the current rating on the ubec22 and ubec-uvc?

  • The ubec22 will work up to 22A on 8S.
    The ubec-uvc will work up to 22A on 14S.

What do the yellow and black wires do on ubec-uvc?

  • They are for higher current draw (10A)

Where can I download the KDE Device Manager?

  • The KDE Device Manager can be found under the Specifications tab for the KDEXF-DMA and the KDE-DMS

Troubleshooting for the KDE Device Manager?

  • Instructions:
    1) Try connecting a recommended battery to your ESC and connect it to your computer to ensure that the ESC is getting enough power. The USB cable “should” supply power however, USB hardware and Power Management settings can limit USB power. If the computer still does not recognize the ESC, try using a different USB port.
    2) If unable to install the KDE Device Manager, try deleting previous versions by deleting the KDEUpdate folder (C:\Program Files\KDEUpdate). Verify that anti-virus software isn’t blocking the KDE Direct Device Manager as an unrecognized app.
    3) Reinstall the KDE Device Manager and verify the driver files in the installer were installed (after accepting to install the drivers you should see a green check mark next to each one indicating that it installed successfully).
    4) Try disabling fast startup in Windows. When fast startup is enabled the operating system can retain mutually exclusive locks on files.
    5) Restart Windows.
    6) Verify that your computer recognizes your connected DMA/DMS. This can be done by accessing the Device Manager within the Control Panel on Windows. When you connect your ESC, the Device Manager may display a warning icon with the message "Unknown device". If this occurs it means that your drivers may not be installed correctly or have become corrupted. When the DMA is connected, you should see the connected device under Ports (COM & LPT) -> Silicon Labs CP210x USB to UART Bridge.
    7) To use repair mode: Check the repair mode checkbox before connecting the USB cable to your computer. Then click the update firmware button.

What do the settings in the Device Manager do?

  • All settings in the KDE Device Manager are specified in the Instruction Manual. Review all of the Advanced Setting options for optimal operation or customize to your own requirements.

My ESC does not have programming leads. How do I program it?

  • If your KDE Direct ESC does not have a programming lead, you can try programming it through the control lead (white, red, black).

My system experienced a thermal induced shutdown. Is there a way to do soft shutdown for the thermal protection?

  • The thermal induced shutdown can’t be changed. It is built into the MCU as a method of self-protection that activates upon reaching 95°C temperatures. Make sure that the ESC is properly ventilated while operating, and that the ESC is properly suited to handle the power inputs. If you are using an underrated ESC for your system, it is recommended to exchange the ESC with one that has higher operating capabilities.

What are the maximum voltages for KDE ESCs?

  • The ESC lines and their max voltages are specified below:
    KDEXF-UAS: 35V rated 40V maximum (limitation of the MOSFETs)
    KDEXF-UASHVC: 55V rated, 60V maximum (limitation of the MOSFETs)
    KDEXF-UASUVC: 63V rated, 63V maximum (limitation of the capacitors, uses 80V MOSFETs)
    We recommend a 10% margin minimum for the regeneration-capability of the ESCs, as the voltage will increase during regeneration phases.

Will the system be harmed by running close to the failure voltage on KDE ESCs?

  • For safe operation, do not exceed the rated-voltage for the ESCs. Running higher than specified voltages on the ESC will damage the MOSFET channels from voltage ripples and regeneration phases. The ESCs are designed to operate safely at and under their ratings. The primary limitations are the internal components (ICs) primarily capacitors and Mosfets.

My ESC will not arm with my flight controller but works when connected to a servo-tester. What is going on?

  • If there are no problems running the ESC via an individual servo-tester, then something is wrong with the electrical connection (control lines) between the ESC and flight-controller. Please refer to these items for more information:
    Power System Testing (YouTube)
    Instruction Manual

Is it possible to run two KDE brushless motors off of one ESC?

  • It is technically possible to run two motors off of one ESC. However, if a single motor loses timing from any external factor, it will not regain the timing and the second motor may also lose timing. An external factor may be any event that causes one motor to rotate differently that the other.

My KDE Direct ESC is running hot to the touch at 30% throttle. Why is this occurring?

  • One of the reasons for the higher-temperatures is the low-hovering throttle, 30% is below the optimal range of 45% to 55% hovering in UAS multi-rotor applications, so the ESC is required to displace more energy during the off-cycle than the on-cycle (termed partial duty-cycle in BLDC controls). If you are able to run your system at a higher-throttle percentage, you will notice lower-operating temperatures on the ESC (even at a higher-amperage draw) than running at the low-throttle ranges.

How can I calculate the mechanical RPM from the eRPM lead on a UVC series ESC?

  • The eRPM lead generates a pulse width with a period that decreases as the eRPM increases.
    One way to view this pulse width is by connecting an oscilloscope (brown to GND, signal to ORANGE)
    The circuit is powered by the ESC internally so there is no need to connect to the RED wire.

    The mechanical rpm can be calculated with the following formula:
    mechanical rpm = 1 / period * 60 * 2 / # magnetic motor poles.

    We send 1310us to a 5215-330 motor.
    The eRPM has a period of 1.60ms
    mechanical rpm = 1 / 0.00160 * 60 * 2 / 22 = 3409 rpm

How long can I record data on a UVC series ESC?

  • At 1Hz the ESC can record data for 100 minutes.

Where can I order KDECAN bus cables for telemetry for the UVC series ESC?

  • The CAN bus wire kit can be found here

How can I enable telemetry on the UVC series ESC?

When does thermal protection occur?

  • The MCUs in KDE ESCs will shut down at 95 ºC (203 ºF)

Can I extend the ESC battery wires or DC leads?

  • We recommend extending the ESC motor wires instead. Lengthening the ESC battery wires will cause higher voltage spikes induced in the wires and on the input capacitors. This will cause premature wear on the capacitors and other sensitive components inside the ESC. If you extend the battery wires, adding additional capacitors every 8-12 inches is necessary to compensate for the additional wire inductance. If you are extending the ESC battery wire you need 2.35uF per amp per inch. For example: 2.35uF * 85A * 24 in ≈ 4,800uF per ESC spaced evenly along the DC lines.

How do I use an Arduino to generate a PWM signal for automated testing?

  • Typically throttle control is managed by a flight controller and RC controller.
    KDE Direct ESCs will work with any device capable of generating a standard PWM signal including Arduino based microcontrollers.

    Some sample code is listed below that will work with an Arduino Uno. Alternatively, there is also the Arduino Servo library:

    // To connect the throttle control lead to the Arduino, connect the white wire to digital pin 9, red wire to 5V, black wire to GND
    int pwmPin = 9; // PWM is connected to digital pin 9

    void setup () { // arm the ESC by sending min for a few seconds

    void loop () { // go from spin to max
      for (int fadeValue = 144; fadeValue <= 243; fadeValue++) {
      analogWrite(pwmPin, fadeValue);

How do I connect KDE Direct ESCs to the Holybro PM07 (Pixhawk 4  power module)?

  • See the diagram below for reference:

How do I convert PWM pulse width (μs) to throttle (%)?

  • If the throttle range is 1000-2000 then every 10μs represents 1%. If the throttle range is 1100-1940 then 1100 represents 0% and 1940 represents 100% then:
    PulseWidth = 1100 + 8.4 * Percentage
    Percentage = (PulseWidth – 1100) / 8.4
        1100 + 8.4 * 90 = 1856μs
        (1310 – 1100) / 8.4 = 25%

What is the ESC temperature rating?

  • The ESC can operate at temperatures as low as -25ºC and as high as 95ºC however, in a system the least rated component will be the first to fail. At lower temperatures supplying power becomes an issue as the drain current will be higher. The minimum discharge temperature for most LiPo batteries is typically around -20ºC. Please consult your battery specifications for an accurate rating. If you fly below this temperature, the batteries may not supply enough power. Insulating the batteries might allow lower temperatures. The storage temperature of the ESC is -40ºC to 105ºC.

How do I ensure the motors don't spin while doing safety checks?

  • It's NOT possible for an ESC to spin a motor if it isn't armed, if it isn't receiving a throttle signal, or if the signal the ESC receives is less than the spinning throttle signal. If you want to ensure that the motors will never spin while doing pre-flight checks then you need to make sure that the flight controller never sends a throttle signal greater than 3%. More information can be found here.

At what temperature does S.R Braking Activation occur?

  • Precision: enables synchronous rectification immediately.
    Dynamic: enables synchronous rectification when the ESC reads a temperature of 10ºC above its initial temperature.
    Balanced: enables synchronous rectification when the ESC reads a temperature of 15ºC above its initial temperature.

How do I ensure that the motors have a smooth startup every time?

  • If the throttle is less than 10%, then the motor might not startup as smoothly because there is lower torque to overcome the load/resistance on the motor. A smoother startup can often be achieved by sending a higher throttle during startup.

How do I use OneShot125?

  • OneShot125 works with Throttle Calibration Mode DYNAMIC.

What is PWMSync?

  • PWMSync is a PWM protocol where the PWM output is synchronized to the flight controller's gyroscope. The output rate is 500Hz, the same as the gyroscopes update rate. All KDE Direct ESCs work with PWMSync.

When should the ESC be replaced?

  • The ESC should be replaced after 4000 hours of operation

Can the ESC's be controlled bidirectionally (forward & reverse)?

  • Firmware to control the ESC clockwise and counter-clockwise is available on request

How do I control the ESC with a duty cycle?

  • Example: An 1100us pulse width at 50Hz will produce 5.5% duty. [ 1100us = 0.0011sec, 50Hz = 0.02sec, (0.0011 / 0.02) = 5.5% ] An 1100us pulse width at 400Hz will produce 44% duty. [ 1100us = 0.0011sec, 400Hz = 0.0025sec, (0.0011 / 0.0025) = 44% ] In this example the 5.5% duty spins the motor at the same speed as the 44% duty. This is because the ESC does input capture on rising and falling edge detection.

What type of batteries do the ESCs work with?

  • The ESCs work with LiPo, LiHv, Li-ion, LiFe, NiMH, and NiCd batteries.

How does the ESC control speed?

  • All KDE Direct ESC’s use voltage mode control. The pulse width of the input signal (400 Hz PWM) represents the input throttle (0-100% motor speed). The input pulse width determines the duty cycle of the output signal (16 kHz PWM). For example 50% throttle means 50% power (voltage modulation to the motor)

How do I use 2000Hz PWM input with the 20LV ESC?

  • OneShot125 works up to 4kHz frequency

Do you have an example of KDECAN?

  • An example with an Arduino can be found here

What is the lifespan of components?

  • For motors: Many customers have run our motors for over 1,000 hours without performing maintenance. Our motor designs use certified NMB and NSK brand bearings which have a rated lifespan of 200 hours so we recommend replacing the bearings after that time. Environmental operating conditions also significantly impact the life span of the motors (salient or dusty operating conditions, temperature, humidity, vibration, loading, etc.) Routine maintenance checks are important. Make sure the bearings aren't grinding, there is no play between the motor bell and shaft/collar, and the motor windings are not dark or corroded.

    For Propellers: inspections should be performed to ensure the overall condition of a propeller's airworthiness. Lifetime on props greatly depends on how they are stored. Carbon fiber can last a long time but the resin can break down with exposure to moisture/water which can lead to delaminations. Sunlight / UV light can also break down the resin binder overtime. Propellers should be replaced if cracks or nicks are found as these can reduce the props structural integrity.

    For ESCs: They should be replaced after 4000 hours of operation.