• Setting up SBUS with Naze32,Cleanflight, OrangeRx, Turnigy 9XR


    There’s lot of posts and information out there on how to use Naze32 with Sbus but still I found myself having to do a lot of research and guesswork to make it work on my setup. I figured I’d make it easy for the next person with the same gear or at least bring one more puzzle piece to the solution on how to make it work on your setup. In this guide I will go through:

    1. Setting up the 9xr transmitter
    2. How to bind your transmitter and receiver
    3. How to electrically connect receiver and Naze32
    4. How to set up Naze32 in Ceanflight to use the SBUS as rc input

    Here is a list of what gear I use which is used in this guide:

    You will need to invert the logic level of the SBUS signal from the reciever to the Naze32. I made my own inverter which I will explain but you would save some time on just buying a premade inverter such as this one recommended by Cleanflight wiki: ZYX-S S.BUS Connection Cable.

    It should be noted that it probably doesn’t matter what reciever you use as long as it has SBUS support.

    1. Setting up the 9xr transmitter

    1. turn on the 9xr
    2. after the splash screen, press right button
    3. choose which model to use by pressing right
    4. click right button once so it says “2/11″ in the upper right corner

    Change to: ppm, 14ch, 300µSec, 12.5ms

    I noted that some settings will make the DSMX module “angry” and then it wouldn’t send anything. if this happens you need to change back to some settings that works and restart the 9xr. If the module makes a high pitch beep(1/2 a second) and blinks green( three quick blinks every 2nd second ish) when it starts it means it’s working fine.

    2. How to bind your transmitter and receiverbind plug

    This step is pretty straight forward, but I include it for completeness.  You need some +5v and GND to power the receiver. Easiest is to power it from an ESC.

    1. Start with everything powered off.
    2. Disconnect the motor from the ESC and make sure the motor leads isn’t touching anything.
    3. Put a bind plug in the bat/bind port of the receiver.
    4. power up the ESC by connecting it to a battery
    5. Plug in the servo lead from the ESC in the receiver in any port on the receiver to power it up. Usually it will blink orange rapidly.
    6. hold the bind button on the module(the thing in the back of the 9xr) while powering it on. hold until it starts beeping and blinking.
    7. after releasing the bind button on the module, the receiver will normally turn to a steady light wihin seconds which indicates that the binding is complete.
    8. switch off the receiver( disconnect from ESC) and remove the bind plug.
    9. switch off the 9xr.

    3. How to electrically connect receiver and Naze32

    There will be 3 wires connecting the Naze32 and the receiver; GND, +5v and signal. Either you buy the inverter module, in which case you simply connect it in between the Naze32 and the receiver.

    Logic inverter

    It is possible to build a logic inverter with many different transistors, like a N-channel MOSFET for example. Just google “logic inverter npn” or “logic inverter N-channel MOSFET” or similar depending on what you got available and you will find a schematic.

    For the inverter I built,  I used this NPN transistor, a SMD 1k Ohm resistor and a SMD 10k Ohm resistor. I soldered the components according to this scematic:

    Connecting stuff

    The input of the logic inverter comes from the reciever, and the output goes to the pin marked “5” on the backside of the naze32.

    Backside of Naze32 rev5

    The pad marked “5” to the right is the one to connect the inverted SBUS signal.


    4. How to set up Naze32 in Cleanflight to use the SBUS as rc input

    1. In the Ports tab, set UART2 to SerialRx
    2. In the Configuration tab, click the RX_SERIAL radiobutton and select SBUS from the “Serial Receiver Provider” list. don’t use Softserial.
    3. Check if it works in the Receiver Tab!


  • 3d printed landing gear for 420 gram 250-size quadcopter

    The stock landing gear of my 250 tarot was too large, heavy and would get caught in grass in fast forward flight. The situation demanded upgraded landing gear!

    What I wanted to accomplish was to avoid the landing gear to hook onto things on the ground. it should be cheap, light, flexible, crash proof, aerodynamic and also easy to change!

    I got inspired by this Youtube video but wanted something more slim 

    Here is the 3rd iteration of my design

    Do it yourself! Here is the source file and stl file for use with a 3d-printer.

    The design is 3d-printed with ABS plastic and it only takes a few minutes on our Bukobot-8 to print out a new set. I attach it with some hot glue and a zip-tie to the frame. After a crash it’s very easy to peel off the hot glue from the carbon fiber plate to change it for a new one. If you have problems getting old hotglue off, put it in the freezer for 5 minutes and try again, it will be a lot easier!

    240fps slow-mo drop:

    I found that they will brake a bit too easily when i crash with the current thickness(0.6mm), but I find that I rather have to change the landing gear every now and then than having something heavier on, and if it breaks it means it absorbed some energy!

    After crashing from more than 5 meters altitude onto a football field


  • The Key to building a succesfull robot


    It’s key to make things adjustable in your hardware. A good example of how devastating it can be to forget this can be seen in this clip:

    the robot to the right have the wheels too high up, so the magnets are in contact with the dohyo, and the wheels just spin in the air. probably they adjusted the height once on a table, but with the forces from the magnets, they chassi bent and needed re-adjustment. important things to make adjustable: plow height, motor mount, wheel height. with tons of unknown parameters, it is impossible to design something that will have the right settings directly


    you find yourself grinding and fileing things a lot of the build time on your first robots, and the reason is the optimism about how things will fit in eachother. if you cnc-cut things, a “coincident” contact surface in CAD will have high likelyhood to cause problems.

    Iterative design

    go through many iterations, ask others about their opinions and don’t stick to one design just because you spent time developing it, if it turns out to be a bad design making a detailed design will take more time to implement, but will save time in the end, by not just having rectangular blocks stuffed together you will realize problems before you manufacture.

    Design first, then buy&build

    design and browse for parts simultaneously. don’t buy stuff before the design is locked down, unless it’s cheap. try to make design decisions based on available hardware.

    Spare parts

    get spare parts for everything. things will break, and they will break when there is no time to order new ones. a lot of robots have been stranded because one part got broken. it’s worth the extra cost in the time you will save.


  • Lilla Lisa Specs


    Turnigy L3040A-480G Brushless Motor

    Model: Turnigy L3040A-480G Brushless Motor

    Specs: kv :480 rpm/V

    max current: 52A.

    suitable for 6s system (22.2V)

    You can calculate the torque constant, Kt, given the kv:


    at 52A: M=I*Kt=52*0.02=1.04Nm

    gear ratio of 10:35 gives:

    Mout=1.04*3.5= 3.64Nm

    M=F*r –> F=M/r=3.64/0.02=182N

    two motors: 2*182N=364N

    so it is able to push forward with about 364N at full current at both engines. however we dare to push much more current for a short duration


    the motors have a 5mm axle, we picked regular rc buggy pinion steel gear for use on the motor shaft, 10t and mod1 the motor gear has a direct drive on the wheel gear, a 35t mod1 gear from sdp-si of stainless steel. the wheel gears were modified (not the teeth)with cnc to minimize weight and to fit nicely with the rims. the rims are cnc cut from both sides from a piece of Nylon. nylon turned out to be very hard to work with and i had some failed pieces before I figured out a good manufacturing method. the wheel gear is slided on the hub, and fastened with a handful of m3 screws threaded into the nylon. a mold was milled from 8mm sheets of PC and used to mold polyurethane on the rims. a wheel diameter of 41mm was used. with a 4.5mm thick polyurethane tire. the tire is expected to compress about 1mm as they touch the doyho.

    wheel curing polyurethane tires SAMSUNG



    1.3 Ah 6s nano-tech

    we have one individual battery pack for each motor, each is a 1.3Ah 6s(22.2V) 45c – 130c turnigy nanotech


    Motor controllers (ESC)

    the motor controllers are a custom design by Benjamin Vedder. they turn out to run our motors perfectly sensorless, but we will anyway probably

    put in sensors in the motors, by putting hall-sensors between the coils.


    magnets were sourced from http://www.magnetvaruhuset.se/

    we chose the type “super-flatgripare” with threaded tap. these are high quality and very strong!

    diameter: 16mm

    rated attraction force: 10kg


    treads: M6

    price:28SEK each

    after experimentation i’ve evaluated them to give a force of up to about 7 kg each on the dohyo. however, the force is drastically decreasing with increasing distance, e.g. 0.1mm apart from dohyo might just be about 2-3 kg force left. there is space for up to 35 magnets, but in reality about 10 slots are not used ( could be used if more magnetic force is found needed). The “center” of magnets lie about 1/3rd of the distance between wheels and plow, measured from the wheels


  • Linefollower airflow simulation

    i did a quick and dirty check on how the undercarriage shape affects the pressure and thus the downforce. what i wanted to know was: can you assume that the pressure difference the fan creates is maintained under the entire hood, or is the vacuum decreasing towards the edges – and what kind of downforce can be expected?

    i’ve learnt that the shape of the underside of the hood plays a major role in the downforce generated, as you can see in the picture bellow, the fan creates a difference of about 300Pa, but the major part of the undercarriage is only experiencing a mere 60 Pa pressure difference. more investigation needed!


  • Linefollower beginning calculations

    since competing at RobotChallenge 2013 in Vienna with Sleipner and Lilla Lisa, i’ve got more and more excited about building a linefollower.

    initial design-goals ( preliminary)

    200g mass

    3g acceleration sideways as well as accelerating/deaccelerating (all the way up to top-speed)

    more than 5m/s top speed

    vacuum fan. probably a 35-27mm EDF

    size of max 25 x 25 cm to be able to compete in Robot-SM, Stockholm Robot Championship, Robotex and RobotChallenge

    (just for calculations) wheel radius: 1cm

    2s lipo

    rought estimate of suitable components:

    rpm on wheels at 5m/s: 4800rpm

    since 2s lipo –> ca 7.4 volt system –> 4800/7.4=650kv on motor or equivalent with gearbox

    power out of engine at 5m/s, 3g(=30m/s^2): P=F*V=m*a*V=5*30*0.2 =30W = 15W per motor

    since there is no lightweight 650kv, 15w motors, i’ll have to use a gearbox. i like brushless outrunners, there are lots of variations but i’ve found some ca 10g 15W motor with about 2000kv, so a gear ratio of about 3:1 is needed.

    2s lipo ,350mah, 65c 130c burst = 22A continous= 170W kont, 34g. http://www.hobbyking.com/hobbyking/store/__19117__Turnigy_nano_tech_350mah_2S_65_130C_Lipo_Pack.html

    ESC wheel engines: 2s, 10A, 8g http://hobbyking.com/hobbyking/store/__23766__HobbyKing_Brushless_Car_ESC_10A_w_Reverse.html

    ESC EDF: 10A, 9g http://www.hobbyking.com/hobbyking/store/__659__TowerPro_9g_w12A_Brushless_Speed_Controller.html

    EDF: 27mm, 2s, 5.5A, 40W, 8g


    wheel motors: http://www.hobbyking.com/hobbyking/store/__5358__18_11_2000kv_micro_brushless_outrunner_10g_.html

    CAD for motors: https://grabcad.com/library/micro-brushless-motor-1


    bearings: http://www.kullager.se/sv/product/501/Kullager-623-3x10x4


    so far it seems as if 200g total is a reasonable and achievable goal. i will research more what kind of “diffusor” style undercarriage is the best shape to get as much downforce as possible with the EDF as a vacuum fan.

  • Meta-post

    I’ve made one attempt on blogging before, that didn’t go too well.

    Now however i feel i had a need for a blog, my vision for this blog is a way to document primarily projects i undertake, but also to share things i learnt and help others.

    So let’s get to it!

    these are the mentionable project’s I’ve been involved in so far:

    DeathCounter, Festmaskinen, Döbbeldäcker 3000, Quadcopter ( probably the only project i have not yet found a good name for), Gulliver, Sleipner(benjamins postsshowoff video), Lilla Lisa, Bikelights.
    I hope I’ll find time to write more about each and every of these projects in separate posts.
    ongoing stuff:
    Chairman in Chalmers Robotförening, trainee in Chalmers Student Formula, learning the STM32F4, Lilla Lisa ( I plan to put a STM32F4 Discovery in this sumo and develop the code running on it myself as a first project), Quadcopter – design phase is basically done and i just need to find time to manufacture it, put in electronics, test, crash, repeat. Linefollower.
    let’s hope this get’s interesting!