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Newbie Questions

foresterdroneforesterdrone Club Members Posts: 16

I am quite new to building drones. I hope this questions are not so annoying:

1. I am buying the KK 2.1.5 flight controller. Its input voltage is 4.8-6.0V, but my battery has 7.4V, two cells. Could this harm my flight controller in any way?

2. I understand that it is recommended to use a power distribution board, connecting the 8 positive/negative cables from the ESC's to it. So my question is, do you also connect the battery to the ESC? or would you connect your battery to the flight controller? Because if I connect it to the ESC how would it supply power to the flight controller?

3. Do you recommend using bullet connectors? Which part of the ESC has the female and male bullet connector? Should I only connect the ESC to the motor with bullet connectors or is there anything else that it is recommended to use bullet connectors?

4. I bought a 20amp with a BEC of 3 amps. But the input voltage is 4.8-6.0V of the KK flight controller, will that be a problem?foresterdrone2016-05-22 03:46:25


  • WTWUKWTWUK ✭✭✭ CornwallClub Members Posts: 13,511 ✭✭✭
    It ain't a drone! It is a multicopter, UAV or anything BUT A DRONE! Grrrrr!!!

    Anyways, to answer you.

    1. Your battery will kill the KK faster than you can blink if you connect that battery to it. 6.0V is the ABSOLUTE maximum you can power it with. And your 7.4V 2 cell battery is going to be 8.4V when it is fully charged by the way.

    2. Use of a power distribution board is entirely optional - it is one of several ways to wire multirotor power setups.

    If you use one, not only do you connect the 8 ESC pos/neg wires to it, but you also connect a pos/neg lead with the relevant connector for your battery on one end so you can connect your battery to the power distribution board. That is indeed the way you get power to the four ESC's. The power for the Flight Controller will come from the BEC if it is in the ESC, or via a separate BEC if not, that is connected pos/neg to the Power Distribution Board.

    3. Either use bullet connectors, or don't. Your call. If it is a small 250 or less sized machine, for weight reasons don't. Solder the connections and cover the joints with heatshrink sleeving.

    ESC's in general do not come with connectors. If you want to use connectors, females go onto the three wires the motors connect to. Males would go on the other end (but not is you use a Power distribution board that requires the pos/neg leads to be soldered onto it.)

    4. The Amperage of the BEC has nothing to do with voltage. All that figure means is the amount of Amps that the BEC can have taken from it. Under 3Amps fine. Over 3Amps = fried BEC in the end.

    and ....

    5. You need to read up an awful lot more before spending too much money on the wrong/not needed stuff. WTWUK2016-05-22 06:38:47
  • foresterdroneforesterdrone Club Members Posts: 16
    WTWUK thank you so much for your reply. It really helps out. I am a bit confused with the 3 amps current, how would I make sure that the current remains under 3 amps if the ESC's are connected to the power distribution board. Also for #1, wouldn't the BEC in the ESC's act as a voltage regulator?

  • WTWUKWTWUK ✭✭✭ CornwallClub Members Posts: 13,511 ✭✭✭
    The 3Amps rating will be far and away sufficient to run the electronics on the copter - you will not even get up as high as 1.5Amps. The BEC does not 'push' Amps out- it is the things connected to it that 'pull' Amps. And that will not of course be the motors, as they are on a different power circuit than the BEC inside the ESC.

    Now, as the ESC's you mention have a 5V 3A BEC, that will run the KK and your receiver, and is a crude sort of voltage regulator as you thought.
  • foresterdroneforesterdrone Club Members Posts: 16
    Thank you so much for your help. Also, you recommended to read a lot, can you give me some starting points on what topics I should read first?

    So female connectors go on the ESC and male bullet connectors on motors?

    Thanksforesterdrone2016-05-23 02:20:56
  • WTWUKWTWUK ✭✭✭ CornwallClub Members Posts: 13,511 ✭✭✭
    Read anything you feel useful that can be found using Google. If you do that, you will pick up all sorts of things you have never even thought of as an added bonus!

    Somethings you will discover quite quickly is that you can get a FAR better type of Flight Controller than the KK2.1.5 for less money ... and how diabolical your choice of battery is ...image

    You could start HERE which is a very good write up.

    Correct about the Bullets. It is convention that 'Females' go onto wires that can be, or are 'Live'. Males go on wires that plug 'into' Live things ... exactly the same principle as your home mains plugs and sockets.

    In addition, you MUST use heatshrink sleeving to cover all exposed areas of Female connectors, and the ferrule ( but not the end bit that goes into the female) of Male connectors to prevent them shoring out with anything else. WTWUK2016-05-23 03:56:49
  • foresterdroneforesterdrone Club Members Posts: 16
    Okay thanks. Sorry to bother you so much,

    Another question that I had was how do I know that the max continuous draw of my battery is 192 amps, because I am using a battery with 5.5aAh and 35C. However, my motors, in total, only require a current of 56amps. I am a bit confused about this concept. I know in my motors, the max amperage in its circuit is 15amps. But then how does the amps flow? Does this mean that the battery has a continuous current of 192amps?

    Also, I know my ESC's have the BEC which regulate the voltage to the flight controller. What about the transmitter, wouldn't the voltage of the battery be too much?foresterdrone2016-05-24 00:09:37
  • WTWUKWTWUK ✭✭✭ CornwallClub Members Posts: 13,511 ✭✭✭
    You will know the maximum Amperage a battery can supply by multiplying the capacity x C rating.

    In your case that will be 5500(mAh)/1000 x 35 which = 192.

    Therefore 192Amps is the MAXIMUM your battery will withstand being 'drawn' from it. If you connect it to something that requires say 400Amps for example, the battery will get rapidly hot, and puff up like a balloon and potentially burst.

    If your motors can 'draw' a maximum of 15Amps, the most that all four can 'draw' will be 60Amps and your battery will be very happy and run cool.

    Your transmitter will not be powered by the same battery will it. If it is, you will be needing a very long set of wires to connect it to the uadcopter when it takes to the air ...
  • DaithiDaithi ✭✭✭ Belfast,IrelandClub Members Posts: 8,708 ✭✭✭
    One caveat regarding male and female connctors. Double check with a picture before ordering (or order one set of each). For some strange reason HK, in common with other Far East suppliers tend to refer to them the wrong way round, especially if they come with a 'shroud'.
  • foresterdroneforesterdrone Club Members Posts: 16
    About the bullet connectors, I saw that 3.5mm bullet connectors support a current of 60amps. My motors have a current draw of 56amps. Do you guys recommend I buy bigger bullet connectors to have a little bit more amperage? Like maybe 4.0mm or should I stick to 3.5mm bullet connectors?
  • WTWUKWTWUK ✭✭✭ CornwallClub Members Posts: 13,511 ✭✭✭
    3.5mm are fine. Each motor should not be drawing anywhere near 56A by the way.
  • foresterdroneforesterdrone Club Members Posts: 16
    Awesome thanks.

    About the lipo battery charger, I was doing the math to determine the amount of watts I need to charge my battery(3S 5.5Ah). So I need about 61 watts and 5.5amps from the lipo charger. I found a 80watts lipo charger with the following specifications:


    Operating voltage range: DC10.0-20.0 Volt / AC to DC adaptor(DC10.0-20.0V/6A)

    Circuit power: Max.charge power 80W / Max.discharge power 10W

    Charge Current Range: 0.1~6.0A

    Discharge current range: 0.1-2.0A

    Current drain for balancing Li-po: 300mAH/cell

    Li-ion/Polyment cell count : 1-6 series

    NiCd/NiMH battery cell count: 1-15cell

    Pb battery voltage: 2~20v

    Dimensions: 133x87x33mm

    It is perfect for what I need. However, I do not have a power source to connect it to, so I was thinking of buying a AC/DC adapter. I found this adapted, which is within the input voltage of the lipo charger:

    However, it is only 72 watts.Would that work properly? How will this affect the charger's performance? Do you have any other suggestions for powering the lipo charger?

    Also, I wanted to ask you what type of wire is used to connect the battery to the power distribution board. I was thinking of using a 14AWG wire, solder to the power distribution board, soldering a male XT60 connector to the other end, which would allow me to just plug in the battery, since my battery has a female XT60 connector. However, I don't know if that wire is too thick or if the approach I am planning on using is not efficient. What would you recommend?

    My battery is this one:


    Thanks :) sorry for being so annoying.foresterdrone2016-05-24 11:24:31
  • __Evan__Evan Club Members Posts: 1,122
    You don't need a 61W charger to charge that battery. You could use a 10W charger if you wanted to - it'd just take ages (about seven hours, at a rough guess). However, having a charger that can manage at least 1C (5.5A in this case) will get the fastest charge time without damaging the battery. The 80W one you've found will be fine, but I'd also consider just getting a cheap 50W/5A one - it's only going to take marginally longer to reach full charge.

    With the power supply: it'll work fine if you don't let the charger go over 72W. If it's charging a 3S battery at 5.5A this shouldn't be an issue. However, I'd be more inclined to spend a few dollars more on a 10A 12V model. There's plenty on eBay (eg. here for $14.99). That gives you a bit of headroom (some of these cheap power supplies may not be happy running at their full rated load for a long time), and it opens up the option of having two chargers on one power supply (eg. main battery + RX battery charging at the same time).
  • foresterdroneforesterdrone Club Members Posts: 16

    So I have this problem. I got my motors and I am looking to mount them onto my frame. I got the motor mount:


    So first I tried to use the inner holes to place the screws and connect to the motor, then use the outer holes to connect to the frame. However, my frame is too small for the outer holes:


    So then I just placed the screws directly on the frame to the motor screw holes. I do not know if this method is too safe, I don't want my motor to fly off. So I was thinking if it was okay to pass a zip tie through some of the holes on the lower part of the motor:



    I don't know if attaching the motors to the frame without a mount, directly with the screws, could damage the coils or the motor. I am also not certain if the zip tie on the motor holes could damage the motor. I want to ask you guys for your opinions on what is the best approach to this issue.

    BTW: I only have two screws and one zip tie because I want to see your opinion before I make any other changes, but eventually I am planning on screwing the four screws and probably two zip ties.

    Thanks.foresterdrone2016-05-27 05:02:13
  • WTWUKWTWUK ✭✭✭ CornwallClub Members Posts: 13,511 ✭✭✭
    You do in fact mount the motor with just the scews. Better still is to use the correct size socket head (allen) screws with a washer under the heads. But whatever screws you use, you MUST use threadlock fluid on them. Remove the cable ties. They will not help.WTWUK2016-05-27 06:07:46
  • foresterdroneforesterdrone Club Members Posts: 16
    Ok thank you,

    So placing two cable ties on both sides will not be beneficial as a backup plan in case the screws are loose? Also, I 3d printed my frame:


    For connecting the arms to the center plates, do you also recommend using socket head allen screws, what material do you recommend using? would nylon screws hold up?

  • WTWUKWTWUK ✭✭✭ CornwallClub Members Posts: 13,511 ✭✭✭
    Metal socket head screws. Nylon ones will break in seconds.

    The cable ties won't help. What will is making sure the screws don't come out. Loctite is the answer.
  • foresterdroneforesterdrone Club Members Posts: 16
    Can Loctite be used on plastic or will it eat up my 3d printed frame? I was reading some posts about the use of loctite on plastic:

    However, I don't know much about it, what do you think?foresterdrone2016-05-27 09:43:14
  • WTWUKWTWUK ✭✭✭ CornwallClub Members Posts: 13,511 ✭✭✭
    You don't use it on plastic. Only on metal to metal.

    Threadlock is used in small amounts - just a smear of it on the screw thread is sufficient to do the job. Not bucket loads of the stuff so that it floods out like glue all over the place.

    As for 3D printed frames - I don't know how they stand up to crashing, or if they are stiff enough. You can test that by seeing if you can twist the arms along their length. If you can using little force, they will be no good, as they will twist in the air when the motors are running and the copter will be a bugger to get flying well.

  • foresterdroneforesterdrone Club Members Posts: 16
    Ok thanks :)

    I have one more question about mounting. I am mounting my flight controller with screws, since my frame has screw holes that fit perfectly for my flight controller.

    However, for the power distribution board, which is located on the bottom plate, I don't have screw holes that line up. Is it fine if I use double sided tape? I don't want to use zip ties over it because I am supposing there is going to be some heat emitted from the cables but I thought maybe double sided tape could be a good solution? Could super glue also work? What is the best option.

    Thanks :)
  • WTWUKWTWUK ✭✭✭ CornwallClub Members Posts: 13,511 ✭✭✭
    Velcro or sticky servo pads aka double sided sticky foam. And you better make sure all rotating assemblies are perfectly balanced if using screws to solid mount the flight controller.
  • foresterdroneforesterdrone Club Members Posts: 16
    Ok awesome. By balancing the rotating assemblies, you mean setting the rotation in the configuration of the flight controller. My flight controller is 45 degrees rotated, is that what you mean?

    Also I wanted to ask you if the rotation of mounting your motors matter. I wanted to mount my motor so the wire is parallel to the arm, but the holes in the frame did not allow me to do this, so the best I could do was this:


    Could this in any way compromise the performance of the flight controller or the stability of the drone?foresterdrone2016-05-29 01:22:56
  • WTWUKWTWUK ✭✭✭ CornwallClub Members Posts: 13,511 ✭✭✭
    Balancing rotating assemblies is nothing to do with the flight controller and how it is mounted - it concerns the balancing of motors, props and motor and prop combinations so they do not vibrate. Think of balancing car tyres and wheels when they place those lead weights onto them to prevent the wheels 'wobbling' at around 60mph (on average!)

    If you do not have things in balance, horrendous vibrations can set in. With multirotors that can cause flight controller sensors like accellerometers to get overworked with the result the copter ends up in pieces on the floor.

    Balancing of such assemblies can be remarkably easy. Google 'EDF balancing using a cell phone'. Even though written for Ducted fans, it can be used with great success for normal props and motors.

    You mounting of the motors is fine. They are all like that.WTWUK2016-05-29 06:05:25
  • foresterdroneforesterdrone Club Members Posts: 16
    Ok thanks, I have heard of prop balancing, but never heard of motor balancer but I will look it up.

    I was also mounting my props on the motors and I am using collet adaptors, what is the best way of mounting them, should I keep the cap loose, mount the adaptor in the shaft and then tighten the cap? Also, it is a bit tight on the shaft, is it recommended to try to push the adaptor down on the shaft as much as possible?

  • WTWUKWTWUK ✭✭✭ CornwallClub Members Posts: 13,511 ✭✭✭
    Yes. Shove the adaptor as far on as possible. Then prop on and tighten up the spinner cone.

    Personally, I do not like that type of adaptor as more often than not they are poorly machined and wobble. That causes all sorts of problems with vibrations.

    Also, make sure all four are fitted the same distance on the shafts - not higher or lower, and to be extra safe, a dop of semi-permanent loctite on the shaft and spinner cone threads is a good idea.

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