After I had a few problems with the standard power module from 3DR and the ones from Hobbyking, like falling off resistors (overheated) and burned out BEC from voltage spikes, I finally designed my own PM modules. The sensor boards are compatible to Pixhawk, APM, Pixhawk lite, AUAV-X2, DroTek und CUAV Pixhack.

These modules are based on a true hall current sensor, so heat is no more an issue !!!

The sensors boards are able for continuous current of 100A for HS-100-V2 and 200A for HS-200-V2 (no time limit), the maximum over current is 1200A@25'C and 800A@85'C for 1 second.

Here some details:

Sensor Board:

  • Current sensor is a “true hall sensor” up to 200A (ACS758-200U) or 100A (ACS758-100U)
  • Ultra-low noise power supply (LP2985-4.0) for current sensor and offset shifting circuit.
  • Microchip MCP601 operational amplifier for offset shifting.
  • LiPo voltage measurement with 1% resistor divider in factor 9:1.
  • 2x10cm / AWG12 cable soldered to current sensor as standard size (Up to AWG8 possible).
  • 6 pol cable connection to Pixhawk / APM (both sides DF-13 connector).
  • 1x 10cm and 1x 20cm / 6 pole cable in the box to select a different cable length if necessary.
  • 18mm x 29mm x 11mm / 7g without cables and shrinking tube.



  • Input 2-6S LiPo / max. 28V
  • Output 5.35V / 3A -> +/- 0.05V –> Ripple 10mV (0.2%) at 1.5A output current.
  • Input wrong polarity protection, as well as Panasonic FM 220uF/35V input capacitor to prevent burn out of BEC from voltage spikes.
  • 4 pole cable to sensor board with DF-13 connector.
  • 47mm x 18mm x 11mm / 8g with cables and shrinking tube.


The Sensor board is installed only into the positive main battery wire and the BEC should be installed as close as possible to the battery connector.


Quality control of the finished product:

To post here all the quality control during the production would be a very long story, so all I can say is, that it is carried out and recorded.

The final QC before the boards are shipped, is a setup with an FC (Pixhawk) and connected to MissionPlanner to check the calibration values for current and voltage measurement.
This final test result will be passed to the customer together with the order confirmation and shipment tracking number by e-mail.

REM: Which power module supplier out there actually use the PM to power up a real FC before shipment ?

So I hope everybody understands, that if I say "safety first"... then I mean it.



Why Hall sensor ?

  • The measurement over a normal shunt resistor is not accurate at lower current (<3.0A). For a Hall sensor the measurement starts at 0.5A with an accuracy of +/-0.5A over the whole range up to 200A !
  • A shunt resistor create heat due to the voltage drop, the hall sensor has only an internal resistance of 100uOhm, so there is no power loss.
  • Due to the heat created by a shunt resistor and the power cable, the measurement of the current is not linear and depends on the temperature. This is not happened to a hall sensor, a temperature change (created by the main LiPo cable) will not influence the measurement.
  • The current flows only through the hall sensor and NOT through the PCB. Most other current measurement boards has the main cable soldered to the PCB and then it goes to the shunt resistor -> these boards can’t handle over 60A constant current ?

Why only a few supplier use a true hall sensor for current measurement in an MR ?

  • Hall sensors are very expensive, compared to a normal shunt resistor and not everybody out there wants to spend the money to top up for a good measurement system. So the sales quantity and profit will not be within the target.

Why output voltage to Pixhawk /APM is 5.35V and not 5.0V ?

  • Pixhawk has internally a 3-way power selector over an ideal diode chip. The 3-ways are USB, power connector (6pin) and the Output PWM rail on the back of the FC. So it is possible to power up the FC with either one of this power sources, but how do we know which power source right know is powering up our FC if there is USB, a PM module as well as an backup BEC connected to the output (ESC/Servo) rail ?
    The answer is easy: Whichever voltage is higher by 0.25V to any other power source is selected as the internal power supply, as long as this voltage do not exceed 5.70V !
    The result in practice on the field can be different, as there are many components connected to the FC like, GPS, Servos, opto ESC’s… etc., the power consumed by the system is not stable, which means the supplied voltage is not stable as well. The reason for this is the loss in voltage due to small power supply cables and maybe many connectors.
    To prevent the internal ideal diode to switch too often between different power sources, we choose a bit unusual high voltage (5.35V) as a main power supply. Which means only if any other power supply (USB or PWM rail) is in the small range of 5.35V+0.25V=5.60V and the maximum voltage of 5.70V, then the diode would switch over to the other source.

Why the cable from UBEC to the sensor board is 4 pol ?

  • To reduce the resistance in the power line and increase the safety, or should we ask, why does the DF-13 power input of the Pixhawk has +/+/I/U/-/- ?
    There are also two wires, for positive and negative, used to reduce the risk of failure.

Why sensor board and UBEC are separated ?

  • A switching power supply can be a very “noisy” part in the power supply chain and it is very difficult to shield the coils (1.5MHz) from the current measurement board. So it was decided to keep the two away from each other.

 Why is there an additional capacitor installed at the input of the UBEC ?

  • Many people complain that the UBEC seems to be bit big, but fact is that he is only 22mm x 17mm. What makes him BIG are the safety capacitors at the input and output !
    We all had the issues before that any ESC burned out due to the “hammer effect” in the supply lines, but do we consider that the UBEC is sitting on the same voltage source ?
    Does anybody ask himself so far why suddenly his BEC burned out ?
    Why does some people add some capacitors onto the ESC’s to reduce the risk of failure, but in the same time they forget that there is also anywhere an BEC in the supply line which might need some protection too ?
    How good is it if your ESC’s survive a voltage spike, but your BEC didn’t and the MR crashes ?
    If you can answer some of the questions by yourself, then you will also figure out why this UBEC is a bit bigger than others.

 How can I get one of these boards ?

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    • The electronic on the sensor board has it's own LDO, so of cause you can use your own BEC. Just make sure the voltage is in the range from 5.0V-5.35V.

      The calibration values, for voltage and current measurement, would be still correct.


  • I've updated the installation wiring drawing of the Sensor Hub X2, a downloadable version of this drawing can be found here:


  • A short presentation about how the Sensor Hub X2 works, when combined with a flight controller, 2 current sensors as well as two batteries connected in parallel.
    Further info can be found here:

  • Sensor Hub X2 to protect paralleled LiPo packs and as an direct replacement for any circuit based on the "ideal diode" design.


    This sensor hub is to connect two current sensors (LiPo's) in parallel. The current of both sensors will be summarized and passed to the FC. The voltage measurement of the LiPo packs will be collected from both sensors and passed through the Hub to the FC.

    The main purpose of this hub is to replace existing protection circuits (like an ideal diode) and to monitor, that both paralleled LiPo’s supply the same current to the system.

    Since we monitor the current of both batteries, we will find out very early when a LiPo starts to fail… before it is too late.

    If the difference in current is bigger than +/- 10%, the Hub will issue a warning to the pilot via a Power Led and/or buzzer (fast flashing) connected to the Alarm I/O.

    If the difference in current is larger than +/- 20%, the Alarm output will be always ON to indicate the fault… the pilot should immediately land and check the batteries.

    Additionally, there is a reserve relay contact (alarm) for the user to implement any desired function.

    The I2C bus is for future integration.

    39mm x 31mm x 6mm / 7g without cables.

    Will try to prepare a short video about the function of this Sensor Hub... post it here when ready.


  • The 2nd prototype for an 2x Sensor Hub is finished and I've ordered the 2nd batch of PCB's today...

    The 2x Hub is mainly for LiPo's in parallel, to observe that both LiPo's supply the same (+/- 10%) current to the system and to recognize in an early stage if one battery is dropping the current.

    It is also an direct replacement to the so called "ideal diode", as we can find out a malfunction of an LiPo battery much earlier, before the system becomes critical and we have enough time for an emergency landing.

    The 4x, 6x and 8x Sensor Hub is either to be used if more than 2 batteries are connected in parallel, or to be installed into the ESC wire for each motor to observe and summarize the individual currents of each motor. -> For the really big MR's !

    Below is a picture of the PCB (only 30mm x 39mm), with the following functions:

    • Current sensor test at power ON -> Failed = Alarm / Ok = Run
    • Current 1 and 2 are summarized to the flight controller: (0-200A)+(0-200A) = 0-400A -> 0-3.3V
    • Analog circuit over 3x MCP601 to keep the signal smooth
    • FMU to measure the current of each sensor separate. -> A bit "big" one, but it will be the same chip and firmware for 4x, 6x and 8x Sensor Hub.
    • Blue LED to indicate operation status (Self test / STBY / RUN / ALARM)
    • Two bight red LED's to indicate wich current sensor gave the alarm during flight. Can be only reset over power OFF/ON.
    • Alarm output 1: +5V / 1A for buzzer and/or power LED.
    • Alarm output 2: Potential free relays contacts: NO-P-NC
    • Alarm output 3: Over I2C to FC (need some research how to implement in APM).
    • Optional LCD display (over I2C) to read out flight data of each sensor (current + voltage).
    • Sensor Hub powered by BEC from flight controller.
    • Current sensors are powered via the Sensor Hub.
    • The standard Current sensors HS-100-V2 and HS-200-V2, as well as the 2-6S BEC and 4-14S HYB-BEC, can be used without modification.

    Interested ?



    Actual size only 30mm x 39mm !!!

    • Hi Christian! You are right! What do you think? When will be HUB available?

      Thank you! ☺
      • Hi Adam, guess 5 days until the first PCB is assembled and firmware coding is done, then at least 2 days for testing... so if everything is smooth, then the hub should be available in approx. 7-9 days. 


    • Just two words....How much?

      • Hi Emin... I try right now to reduce the price as much as possible, as it would be a bit expensive if somebody would like to purchase a complete set with Sensor Hub + 2x Current sensor + BEC or HYB-BEC.

        I will post the new prices here as soon as I got them.

        The 2x Sensor Hub would be anywhere between $15 to $20.

        • Well I definitely want to purchase complete set! :)

          Which BEC would you recommend me?

          Normal or HYB?

          I will probably use two BECs for redudancy... :)

This reply was deleted.