Home Forums Everything about everything else dRonin for Tricopters! (TriRonin)

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    The PDB supplies the 6 Volts needed, not the flight controller.

    BabyPDB – 36x36mm Power Distribution + BEC + Current sensor (REV3)


    I’m using the aio version with no pdb


    I have got it wired the firmware downloaded and the motors spin. Just trying to figure out the servo


    IMO you will need a separate PDB. While most AIO’s can supply 4, 5 and maybe even 6 Volts… They can not supply the “stall” current the Servo will need. If your not aware of what this means then you should research more into how servos work. I will say though, that while you can rum a Servo at a given Voltage, it will burn up easily if the Power supply inst up to the task.


    Ok thanks for the help….. I took power from the unused esc pads and used an ubec…. it’s got 5v going to the servo
    Does that seem like it would work without messing anything up?
    I don’t have a lot of experience with this type of build.
    Previously had a tricopter with the kk2 then went to the cc3d now trying to make this kakute board work


    The Kakute F4 V2 AIO has a Current output of 1.5 A Max on it’s 5 Volt rail. Which is fine for running your Camera / VTX but not much else. That translates to 7.5 Watts for the entire BEC. (Current * Voltage = Wattage)

    Now assuming your using David’s Servo… BMS-210DMH


    This has a Voltage range of 4.8 – 6 Volts and Stall Current of 1 Amp @ 5 Volts. However don’t believe those figures for a moment. I’ve run this Servo using 5 Volts from an Flight-Controller (3 Amps Max) only to burn up a Servo in the process. Part of why is that the Flight Controllers on board BEC can’t maintain that Current especially why it has to support other devices. This tends to pull more power from the BEC than what it’s capable of safely managing. Thus when the available power sags the Voltage pulled across the Servo drops as the current starts to increase. Resulting in a burned Servo!

    That being said, you need a BEC capable of managing 5 to 6 Amps continuous. This will ensure that your Servo is properly fed no matter what the Copter is doing. Furthermore, running the Servo at a higher Voltages is better and here’s why.

    * Higher Torque
    * Better Speed / Response
    * Lower Stall Current draw
    * Overall lower Current draw

    That last point is especially significant due to Ohm’s law. At a higher Voltages the Servo draws less Current to achieve the equivalent Wattage.

    Loose Example…

    If your Servo Ran off of 5V @ 6A this would equal 30 Watts. Yet the same Servo running at 6V would only need 5A to reach the equivalent Wattage. This is important as Current creates heat due to the resistance of the wiring in the system. Lowering the Current results in a system that runs cooler and is less likely to smoke check itself when the Servo Stalls.

    Note: I use the Matek FCHUB-W for my PDB http://www.mateksys.com/?portfolio=fchub-w#tab-id-2

    So yeah… Get a dedicated PDB of some kind (David’s is really good) and run the Servo @ 6 Volts. Otherwise expect to change out Servos due to seemingly “random” failures. (Approx every 2-5 flights)

    Just ask yourself, which is more cost effective… $10-15 for a PDB or $25 for a Servo?




    Ok thanks for the info I’ll order one…


    Heh, didn’t notice the Kakute-F4-v2-AIO had such a poor BEC… I guess it was designed for quads in mind, so didn’t need anything better. That said Matek-F405-CTR’s that I use have 2-3A at 5V, but I guess that is not enough still. Need to find that 6V BEC that I have somewhere in the various boxes… I wonder how much that will affect the servo speed in dRonin? Thanks for the explanation @Kevin_Erik! 🙂



    Well Quads dont have to deal with Servos… Maybe if they did, the support for them would be much better than it is currently.

    Anyways, to best explain our Servo situation you have to know a bit about how Voltage & Current are used. Using the Layman’s analogy of a Garden-Hose… If Water were Electrons, then Voltage would be the “pressure” pushing the Water through the Hose. While Current would be the “amount” Water that has gone thru the Hose.

    From our stand point, we want Voltage and lots of it. Reason being is that it’s the Voltage that determines the rotational speed of a Motor due to the “pressure” of the electrons moving through the Motor-Coils. This directly translates into the Servo’s Reaction-Time and to a certain extent, it’s available mid-ranged Torque. Under high loads the Motors maximum Torque is based on how well it handles Current & disipates heat. This is why most quality Servos have metal casings, to disipate heat quickly. That being said, we need to apply a Voltage as high as the Servo is rated for to maximize it’s performance. Yet keep in mind that while the Voltage is increased, the Current decreases proportionally so long as the Load / Resistance (motor coils) remains unchanged.

    Ohm’s Law https://en.wikipedia.org/wiki/Ohm%27s_law

    This allows the Motor the to use the equivalent amount of Wattage, while reducing the amount of Current passing through the Coils. This is more efficient by reducing the amount of heat-waste lost to the Coils internal resistance. In a nutshell, the Servo’s Motor will run cooler and will have less of a draw on the BEC supply. Typically this isn’t an issue for most Flyers using Servos as the Response-Time and Torque isn’t so critical. Yet for Tri and Bi-Copters we Fly or Die based on the performance of that Servo.

    Now as for why Servos burn up, its simple. Each individual Motor-Coil can only handle so much Current and even then they’re not really made to handle max Current over an extended period. Now while the Motor is spinning this isn’t an issue, as the Coils are being pulsed by the driver card then allowed a brief pause to cool. However, during a “stall” condition, the Motor has either seized or the Tilt-Mechanism is blocked from moving. Thus the entire electrical load is placed on an individual Coil. Causing it to quickly overheat and burn up. Granted there are some more expensive Servos that monitor the Coils to try to prevent this. Unfortunately no system is fool-proof.

    Side Note: All this is one of the primary reasons that Quad users have been moving towards using 6S-LiPo’s from 4S. Higher efficiency, response, power and longer flight times. Hell, the Quads can even be made lighter as the wiring Gauge required for the current draw is reduced significantly. It also stands to reason that a 6S user can get away with a lower “C” rating as well. Thus allowing for lighter batteries to be used.


    Motor 3 is not working properly. When armed it’s spins and then starts getting jerky. When throttle is applied 1 and 2 spin up normally but 3 gets very jerky. When I do the motor setup all 3 run fine and 3 even runs through the entire range of the slider. I’m using aikon ak32 35a esc on 4s I have swapped motors and esc. I took the tricopter apart to make sure there was not a short or something and all looks good not sure where to go from here. Oh yeah all 3 motors are set to dshot 1200 and in configuration they looked mapped properly.


    Sounds like you have one of the following…

    -Too low of a minimum speed set. (part of ESC setting on FC firmware) If thats true, motor will often stutter when copter is armed and RC throttle is at minimum.

    -One or more ESC’s are not sync’d or have differing internal software, timing, Demag settings. All three ESC’s need to have idential software and settings to be able to work together correctly.

    -Bad ESC, try swapping the ESC’s around between motors to see if the problem follows.

    -Screws inserted into motor too deeply contacting the motor Windings inside. (wires shorted)

    -Damaged motor. Ohm out all three leads agaisnt each other. (may require desoldering) You should see very low resistance between each lead. However there should be some resistance as listed on the MFR’s website thats specific to your motor. You can compair one or more motors to get an idea of what this could be if its not listed.

    -Faulty wiring to from the ESC and FC. Chech with Ohm meter for proper continuity.

    -Incorrect motor mapping within your chosen firmware can lead to serious timing issues. IMO this is unlikely if your using mapping thats specific to your application / FC.

    -Check the Flight Controller / ESC’s for metal flakes, poor soldering, shorts and continuity where it shouldn’t be. A dirty solder job can be easily cleaned up with a bit of alchohol and a Q-tip. I have found that an electric toothbrush and alcohol works wonders.

    • This reply was modified 1 year, 12 months ago by Kevin_Erik.

    Thanks @Kevin_Erick I’ll check… though I did swap motors and esc. I’m using the firmware flash that David said in the video for kakute board I’ll try swapping motors again and set the min speed higher as well. Many thanks for all the help. Will post results.


    Swapped esc motor combination did not help. Turned up the idle speed did not work either. Not sure what to do now.


    I took the signal wire off of m3 and put it on m2 and the number three motor spins up and responds to throttle. When I put it back on m3 it fails again. Maybe somehow m3 is mapped incorrect? Though I don’t know why in the output test it works correctly.


    First please verify that you have motors hooked up to M1/M2/M3, and the servo hooked up to the LED pin, not M4. Then can you attach a screen shot of the vehicle pane and the output pane?

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