CT6B “T6” config for KK2 Tricopter

Configuring the T6 transmitter can be difficult due to lack of documentation or lack of experience with RC transmitters.  Mine was both.  Hopefully the info here and the links will help someone else trying to configure this transmitter.

First link: http://www.mycoolheli.com/t6config.html This site has a ton of links and info related to the CT6B transmitter.
Download the drivers for the SILabs CP210 in order to properly utilize the data cable that came with the transmitter.  The driver will emulate a COM port on your PC.

As the transmitter relates to the KK2 controller, let’s look at a few pictures.  Firstly, the most common control layout for a helicopter is Mode 2.
T6Mode

Within T6Config, this is listed as “Model 2”.  You can see how the sticks translate to channels in this diagram.
T6stickmodes

Referencing that picture, you can see what channels control Aileron, Elevator, Throttle, and Rutter.  In Mode 2:

  • Channel 1 = Aileron
  • Channel 2 = Elevator
  • Channel 3 = Throttle
  • Channel 4 = Rudder

Knowing that, we can reference the next picture to know what channels to hook where on the KK2 board.KK2PinOut

Channels 1-4 connect in the same order on the KK2 board.

One thing I realized after getting some flight time is I want the ability to switch self-leveling on or off without using a stick in the arming process.  Since there are 6 channels on the T6, I assigned channel 5 to turn self-level on or off.  Below are screenshots of my configurations in T6 Configuration and Digital Radio.

After assigning channel 5 (note the mixer screens above), connect another signal cable to the AUX input on the KK2 board from channel 5 output of the receiver.  VR(A) can be turned either way, but the switch may not work if VR(A) is exactly in the middle.  Now, flipping switch A will toggle self-leveling mode.

Tuning the KK2 for Tricopter 2.5

The difficult part of the tricopter is not building it, it’s getting it to fly well.  In my opinion, the tricopter itself can be any lightweight monstrosity with some motors and propellers.  Tuning it to fly can be a daunting task – especially for a beginner like me.

The MOST IMPORTANT thing to get out of the way FIRST is motor and prop balancing.  Seriously.  Without ridding your rig of vibration, the KK2 controller will pick up all the shakes from the motors and try to correct them.  This yields a tricopter with a mind of its own, and it’s not a good mind.

First step once built is to calibrate the ESCs.  This video shows exactly how:

Balancing:
After you calibrate the ESCs, it’s time to get the props and motors balanced.  Again, I stress how important this is to good, stable flight.  Below are videos that I found helpful to learning how to balance my motors and props.  I found that the seismometer app was very  helpful in balancing the motors, but not very helpful in balancing propellers.  The vibration from the propeller cutting through air will never allow it ot be completely smooth on the app.


To balance props, go ahead and splurge on a prop balancer.  I bought a DuBro from a local hobby shop and I am so glad I did.  I actually attempted using two razor blades and a straight nail as a homemade rig….that was a waste of time.  Balance props using these methods:

Sensor Calibration:
Go to Sensor  Calibration on the KK2 menu.  Make sure you have your tricopter on a very level surface.  This calibration determines what is level when the copter attempts to self-level itself.  If it is calibrated on a surface which is not level, the copter will try to return to that orientation which results in the copter traveling some direction rather than remaining stationary.  Press continue through the menu a couple times until it’s done.

P-Gain and I-Gain tuning.
Do not attempt to tune these gains and limits until the balancing is done.  I made that mistake and I ended up with a very low P-Gain and a tricopter that could hardly achieve steady flight.

I wondered how to get the voltage alarm to work on the KK2 board.  I never saw a reported voltage and the instructions for the board are hardly an overview.  To get a voltage reading, leads from the battery need soldering on the back of the board.  This video shows how to enable the feature:

Building RCExplorer’s Tricopter 2.5

One day while watching videos on Youtube, I saw an awesome video where a guy attached a camera to his RC helicopter.  He was following a motorcycle, zooming by buildings, and other cool perspectives that would never be possible for the average person with a camera.  This copter gave awesome perspective to ordinary surroundings.  It struck an interest with me and I started looking into what I can do to have a similar rig.  This also seemed like a good new hobby to pick up.

I came across RCExplorer’s Tricopter v2.5 build.  Basically, a step by step of how to build a tricopter (three prop helicopter) along with a parts list.  What could be more simple?  Well, building it is the easy part.  Getting it to fly takes research and some finesse.  Hopefully this blog (build log) will help others as well as help me remember my steps.

Read RCExplorer’s Build 2.5 thoroughly.  There isn’t much I need to put in here about building it that he doesn’t cover.  Any of my notes merely explain why or how I did something differently.  Below is my shopping list from HobbyKing and some notes on a couple items.

Code Qty Description Unit price Total Note
9171000073 1 Hobbyking KK2.0 Multi-rotor LCD Flight Control Board $29.99ea $29.99
TR_P18A 3 TURNIGY Plush 18amp Speed Controller $11.01ea $33.03
07-01002×5 1 Front Wheel Steering Arm & Mount Set 40mm (5sets) $2.41ea $2.41
WHS25-Transpa 1 Turnigy Heat Shrink Tube 25mm Transparent (1mtr) $0.75ea $0.75 Not needed if you leave the stock covering
WH-4MM-BLACK 1 Turnigy 4mm Heat Shrink Tube – BLACK (1mtr) $0.35ea $0.35
DT750 3 hexTronik DT750 Brushless Outrunner 750kv $10.97ea $32.91
BMS-385DMAX 1 BMS-385DMAX Digital Servo (Metal Gear) 4.2kg / .15sec / 16.5g $20.48ea $20.48
R16A483-06 4 Turnigy Pure-Silicone Wire 16AWG (1mtr) Red $1.29ea $5.16
B16A483-06 1 Turnigy Pure-Silicone Wire 16AWG (1mtr) BLACK $1.29ea $1.29
HA0512 1 Hex Screw M3x16 (20pcs) $1.94ea $1.94  I needed longer – m3 or m4 x 30
OR017-01005-M3 1 Hex locknuts M3 10pc $0.79ea $0.79
OR017-01006-M4 1 Hex locknuts M4 10pc $0.79ea $0.79
XT60 1 Nylon XT60 Connectors Male/Female (5 pairs) GENUINE $3.19ea $3.19
S110331-46 1 Scorpion Lipoly Lock Strap 205mm (Small) x 3 $4.90ea $4.90
258000011 4 10CM Male to Male Servo Lead (JR) 26AWG (10pcs/set) $4.00ea $16.00 Only need one bag
AM1001A 1 PolyMax 3.5mm Gold Connectors 10 PAIRS (20PC) $1.46ea $1.46
AM2002-45×10 1 45CM Servo Lead Extention (JR) 26AWG (10pcs/set) $3.15ea $3.15
TR_PC 1 TURNIGY BESC Programming Card $6.91ea $6.91
ACC6 1 Turnigy Accucel-6 50W 6A Balancer/Charger w/ accessories $22.99ea $22.99
74000005 2 1047 (5pcs/bag) $5.98ea $11.96 Order more if you are a beginner. I should have ordered at least 5. If you have experience, get a better brand like APC.
T2200.3S.25 2 Turnigy 2200mAh 3S 25C Lipo Pack (USA Warehouse) $14.04ea $28.08
 9171000003 1 USBasp AVR Programming Device for ATMEL proccessors $4.95ea $4.95  I didn’t order this originally, but should have.

Here are my notes from the build.  Read this before ordering anything:

  • WHS25-Transpa is not necessary if you leave the stock Turnigy ESC heat shrink on.  My soldering iron did not get hot enough to remove the solder for the wire leads that are on the board, so I simply soldered wire extensions onto them.
  • I don’t know why I ordered 4 bags of male-to-male servo cables.  RCExplorer lists qty 4, but this is only 4 cables, not 4 bags.  One bag of 10 is plenty.  Now I have 36 cables I’ll never use.
  • Order a lot of propellers.  Once you start trying to fly, if a propeller hits ANYTHING (leaf, tree, ground), it will crack a piece off and then it’s unbalanced and renders control useless (more on balancing later).  The GWS props that Hobby King sells are the cheapest props you can get.  Use them for training, but buy better props later.  I ended up with APC.
  • I used 20mm hardwood plywood (1/4″ Underlayment) for the center plates and followed the template.  This made the [Hex Screw M3x16] useless due to the extra thickness.  I had extra plywood lying around and it’s still lightweight, so the CNC frame or fiber plate was out.
  • Home Depot has the arms for $.98 each.  They are on the trim and moulding isle with the long dowel rods.  I got square pine dowels and cut them to length.  RCExplorer says 19″, but the dowels are 36″ in length, so I cut them in half leaving two pieces at 18″.
  • Lowes has m3 bolts, Home Depot does not.
  • 4 mm carbon fiber rod was replaced with one 10d nail.  It fit perfectly into the steering mount and the grinding of the end end of the nail off to make it flush with the steering mount heated it up enough to melt the plastic to the nail.  Be careful not to heat up the nail so much so that the other steering mount melts to the nail.  The assembly won’t be able to move.
  • 4 x 3/8 screws used to fasten the servo and the back motor to the steering mount assembly.  Cut off any protruding ends with a Dremel cutoff tool.
  • I used foam pipe insulation for landing gear.  A 6 foot piece was a little over a dollar.  I cut two slits at each end of a 6″ piece and put zip ties through the slits to fasten it to the booms.
  • Zip ties are at Home Depot or Lowes.  I used 4″ mainly, but needed some bigger ones in a couple places.
  • The set (grub) screws on the DT750 are cheap.  Replace them immediately with an M3 bolt of short length.  The factory set screws will crack inside the motor base (see photos).  One of mine is now stuck.  I replaced all the others and the M3 bolt is easier to tighten and works much better. (Lowes has M3 bolts or you can order them from Hobby King here)
  • I finally found the E-Flite EFLM1924 4mm collet type adapter which fits an APC prop perfectly to the DT750.  In case someone says MP-Jet – they don’t fit.

Pictures

Transmitter:
I chose a FlySky CT6B ordered from HobbyPartz.com.  Choose what you like, but for the price and knowing I don’t have any other rigs to fly, this fit me perfectly.  The kit includes a programming USB cable, but be sure to get 8 rechargeable AA batteries.
This link gave me all I needed to program the transmitter (drivers, links, etc.).  You’ll find a little bit of an underground following for the CT6B due to its low cost and usability.  I found that a comparable “programmable” transmitter would cost me no less than $100.  The Turnigy 9XR is a great option, but it doesn’t come with the transmitter module, so that increases the cost.

*Update.  I’ve read a lot about expos (exponential) and programmable curves and I totally understand why this is valuable for flying the copter.  While I only spent $50 on the CT6B, I will get a better transmitter soon.  If you know that this is  hobby you’ll stick with and advance, you can save $50 and get something like a Turnigy 9xr or a Spektrum DX6i.

Power Supply:
This link explains how to modify an ATX computer power supply to supply 12v to your charger.  This is also a good link.  I happened to have a 250w power supply that is rated to supply 9A @ 12v.  This is more than adequate for my 6A Turnigy charger.
The short of what I did:

  • Open it up
  • Cut off the computer plugs
  • Group wire colors
  • Put a 10w 10ohm resistor btwn one 5v and ground wire
  • Mount the resistor near the fan for cooling
  • Tie together the green wire (power on) to a black wire
  • Cap ends of unused wires
  • Use the yellow and black wires to power my charger.

Wiring and Power:
One thing I had to research was how the receiver and KK2 board gets power.  Not having much RC background made this slightly confusing for me.  What I learned is that each Electronic Speed Controller (ESC) has a Battery Eliminator Circuit (BEC) that is either linear or switched-mode.  The Turnigy ESCs in this build are linear and supply 5V to the “M” connectors on the KK2 board.  According to the KK2 documentation, the board gets power from M1 only and M2 up are connected in parallel.  The power received from M1 will also power the Receiver when wired up to the KK2.  What this means in this build is not to worry about power to the KK2 or the Receiver, just wire everything up and it will work – it’s very simple!

This concludes the build of the tricopter.  Next, I will document what I went through to get the thing flying right.

*UPDATE – You may notice that I bought props for only one direction.  I’m reading about the effects of having props go all one direction.  While it doesn’t matter much on a tricopter, a quad requires multi-directional props. What I read so far is that one arm of the tricopter will stay lower when props of the same direction are used in order to counter the rotational torque.  My next prop order will include CCW props to put on my M2 arm and I will update the effects.
This video is a great demonstration: http://vimeo.com/22778782
*UPDATE2 – Get the CCW props!  The copter flies much more level and is steadier.  Definitely worth it.