Home Forums Everything about the Tricopter LR I need help from you, experts! Kakute F4 or Matek F405-CTR? External 5v 5A BEC?

This topic contains 8 replies, has 4 voices, and was last updated by  Kevin_Erik 1 month, 1 week ago.

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  • #63514

    Imetomi
    Participant

    My Tricopter LR frame has just arrived, and I can’t decide what FC to buy. I have built many quads, but this is my second tricopter and I am not so sure about compatibility stuff. I am thinking on buying this

    https://www.banggood.com/Holybro-Kakute-F4-AIO-Flight-Controller-PDB-OSD-Atlatl-HV-5-8G-40CH-Raceband-FPV-Transmitter-for-FPV-RC-Drone-p-1205053.html?rmmds=search&cur_warehouse=CN

    or this

    https://www.banggood.com/Matek-BetaFlight-F405-AIO-Flight-Controller-Built-in-PDB-Matek-5-8G-Video-Transmitter-VTX-HV-for-RC-Drone-p-1194722.html?rmmds=mywishlist&cur_warehouse=CN

    stack for my tricopter and an external 5v 5A BEC to drive the servo. https://www.banggood.com/YRRC-BEC-Module-Board-8-55V-2-13S-Input-5V-5A-Output-1_4MHz-9_2g-for-RC-Drone-FPV-Racing-p-1530386.html?rmmds=mywishlist&cur_warehouse=CN

    What setup do you recommend? Will I miss the SD card feature from the Kakute F4, is that anything useful?
    I am planning to use iNav or ArduPilot (yes, they’re compatible) software on these for missions.

    Thank you in advance!

    #63515

    Kevin_Erik
    Moderator

    While Matek makes great FC’s and PDB’s their VTX’s dont fair so well. I’ve had four / five of them, then had one hell of a time gettig a clear video signal. In some cases the VTX is transmitting on the wrong frequency it was set to. (They get really hot)

    IMO, the best combo is the Matek F405 STD / CTR and the FCHUB-W. Both units can stack together and use a ribbon cable to simplifly wiring. Your servo can connect directly to the PDB headder pins without soldering. While the PDB supplies the 6 or 7 volts needed to run it. This makes for a very easy and clean setup. Which is important when you want to add GPS and a high powered VTX later on. Only issue here is that there are only two ESC pads for the motors. Hence you’ll have to double up on one.

    #63518

    jihlein
    Participant

    I’d go with the FCHUB-W and the Matek405STD. I use this combo in my Tri V4 and it works well.

    I’ve looked at both iNav and ArduCopter for the KakuteF4V2, and I’m not convinced they will work on a tricopter without modification due to the standard way the timer resources are allocated. I’ve made my own iNav target for the KakuteF4V2, which I’ve flown effectively. I’m not sure if iNav is going to pull in the PR for this new target or not.

    I think ArduCopter my require the same/similar mods, haven’t looked there in any detail yet.

    And I think the MatekSTD /FCHUB-W can be used as is without mods.

    #63519

    Imetomi
    Participant

    Thank you! Can I simply solder two ESCs to one pad on the FCHUB-W? Wouldn’t that cause problems or are those pads connected in parallel to VBAT?

    What VTX do you recommend for a long range setup?

    #63524

    Kevin_Erik
    Moderator

    No it wont cause problems… keep in mind that everything is in parallel already. Oh and yes, it’s VBAT.

    #63528

    yumemi5k
    Participant

    Soldering two thick wires onto one pad might be tricky though, as one wire might move when you are soldering the other. I recommend this excellent trick from David from his Flitetest days.

    #63532

    Kevin_Erik
    Moderator

    Just use a thinner gauge wire. In most cases your line losses would be very minimal but this could also save weight on the copter. Keep in mind that, 16 AWG (1.53mm) wire is almost twice as heavy as 18 AWG (1.19 mm) wire. I mention this because all too often folks over do it when it comes to wire thickness and then wonder why the copters flight weight is much higher then they expected.

    The XT60 / XT30 pigtail, should always be either 14 (1.78 mm) or 16 AWG, depending on the size of the build and its “overall” current draw. On some extreme racing builds, I’ve seen 10-12 AWG used. Where the combined burst current can reach as high as 150 amps! However for our purposes, i doubt we’d see more than 30 Amps per motor without some serious throttling. Even then, the majority of the flight would see only just enough draw to maintain stable long range flight.

    If your flying primarily long ranged, then the copter is drawing a lower amount current over a longer period of time. Thus consider using 18 AWG wire between the ESC’s and PDB. For flights that are more likely to see heavy throttle use (higher burst current), 16 AWG is pretty much the standard. You could always see what others are reporting for the overall current draw (during stable flight) and then base your wire selection on that.

    Some insight from JB, https://www.youtube.com/watch?v=KkRBoa3ywyk

    and

    Oscar Liang, https://oscarliang.com/wire-awg-chart-quadcopter-rc/

    Side note: Always use silicone wires!

    #63540

    Imetomi
    Participant

    I would like to use 1700kv motors with smaller 3-4s 20A ESCs which fit better for the frame. Do you think I need more Amps on the ESCs? Many people reported here that their tricopter draws no more than 20A at most.

    #63546

    Kevin_Erik
    Moderator

    You can always ask someone to post their Betaflight log from a flight. This will show the current draw for each motor as well as the peak draw for the entire flight. For 20 ampss draw per motor you could use 18 AWG.

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