setup guide sk 720 flybarless system sk-pb1, sk-pb2 power bus · 2017. 12. 11. · by default, the...

Setup Guide SK 720 Flybarless System SK-PB1, SK-PB2 Power Bus

Rev. 3.99

August 1, 2014 ©2014 Skookum Robotics

1 ©2014 Skookum Robotics, Ltd

Table of Contents Safety Warnings ............................................................................................................................................. 3

Getting Started............................................................................................................................................... 4

Modes & LED Indicator States ................................................................................................................... 5

Installing the SK 720’s Software................................................................................................................. 4

Connecting the SK 720 ................................................................................................................................... 8

Connecting Using a 3-Point Swashplate .................................................................................................... 9

Connecting Using a 4-Point Swashplate .................................................................................................. 10

Mounting the SK 720 ................................................................................................................................... 20

Connecting and Mounting the Power Bus................................................................................................... 26

Proper Servo Alignment............................................................................................................................... 31

Checking Pitch and Phasing ......................................................................................................................... 34

Setting Collective Pitch ............................................................................................................................ 34

Setting Cyclic Pitch ................................................................................................................................... 37


So you’ve decided to go ahead and buy a Skookum Robotics SK 720 Flybarless System – congrats! The SK 720 is a high performance

flybarless controller, providing both flight control and optional self-levelling for electric and nitro RC helicopters. Aside from

superior flybarless control, the SK 720 also features a user interface to help in setting up and tuning the unit, and Setup Wizards to

walk you through the setup steps within the interface. The SK 720’s box contains:

1 SK 720 1 SK PL1 Anti-Vibration Kit

1 USB Cable 1 Decal Sheet


Safety Warnings

RC helicopters are not toys and have the potential to cause serious personal injury and/or property damage. Use

of this gyro places a flight control computer (the SK 720) between the radio receiver and the servos that position

the helicopter’s controls. Loss of control of the helicopter may result if the SK 720 is mistuned or set up

incorrectly.

WARNING: Stand clear! Always test fly in an area away from spectators and keep yourself at a safe distance

when flying the helicopter, especially after any change in the gyro’s setup or tuning. DO NOT stand closer than

10m (30 feet) from the helicopter during test hovers or any other flying. Keep bystanders clear of the flight area

at all times.

WARNING: Always “safe” the motor before you use the PC setup software or SK-LCD terminal to set up or tune

your SK 720. Basic safety practice is to shut down the engine on a nitro RC helicopter or disconnect the motor or

main battery on an electric RC helicopter, whenever the heli is behind the flight line or is being adjusted in any

way.


Getting Started

Installing the SK 720’s Software

To install the SK 720 software to your computer, connect the SK 720 to your PC using the included USB cable. The SK 720 will be

recognized as a mass storage device – open it and find the file named “Download SK720 Setup Software”. Open this link to

download the setup software from our server. After you’ve downloaded the setup software, start the installation and follow the

instructions on the installation wizard. Once this is installed, you’re ready to begin the Setup Wizards and the setup of your SK 720.

If the SK 720’s software cannot open, make sure you are running the latest version of Windows .NET Runtime. See Microsoft’s

website for the most recent edition. You can find the most up to date version of the SK-720’s software on the Updates page of our

website.


Modes & LED Indicator States

The SK 720’s LED indicates the gyro’s current function. The table below outlines the LED’s patterns for each function:

LED State Meaning

Slow Green Setup Mode

Fast Green USB File Transfer

Solid Red Flight Mode – Initializing

Solid Green Flight Mode – Ready to Fly

Green, with Red Flicker Flight Mode – High Vibration Warning

Flashing Red Error State

Alternating Red / Green Firmware Updating – Do Not Disturb

The SK 720 switches to Setup Mode when it is connected to a PC via the USB cable or to the LCD terminal. In this mode the SK 720

provides control mixing, but no stabilizing action – this allows you to complete mechanical setup and servo trimming.

When initializing, the SK 720 needs to be completely still for several seconds. The SK 720 will fly without being properly initialized,

but it will not be in trim – make sure you have a solid green LED before flying!

The most common causes for the flashing red error state are:

• The cyclic stick wasn’t centred during gyro initialization in flight mode

• Your helicopter has onboard electrical system voltage problems.

• The SK 720 is too hot or too cold

• The Micro SD card failed to initialize

Turning the SK 720 off and then on again will clear the error state in most cases.

NOTE: The “green with red flicker” vibration warning indicates that vibrations are too high for self level to function. However, the SK

720’s primary flight control is not affected by high vibrations. Only self-level shuts down during instances of high vibration. The

High Vibration Warning will only appear when at least one Cyclic Bank is set with Self Levelling on.


Below is the SK 720’s software interface, designed and developed for the setup and tuning of your SK 720.

The SK 720’s Setup Wizards provide step by step instructions on using the interface and setting up your helicopter. They must be

completed before flying your helicopter.

Figure 1 - The SK 720’s Software Interface


Following the Setup Wizards ensures proper setup of the SK 720 and your helicopter. You must complete all 4 of the Setup

Wizards before spooling up your heli. If you’re unsure about how to proceed in any of the setup wizards, video walkthroughs of

the wizards (and more!) are available on our YouTube channel at: http://www.youtube.com/user/SkookumRobotics. More

information and troubleshooting tips are available at www.skookumrobotics.com/wiki, and you can reach the Skookum Robotics

team by emailing us at [email protected].

Figure 2 – The SK 720’s Setup Wizards


Connecting the SK 720 Your helicopter’s servos get connected midway through the Initial Setup Wizard. DO NOT connect them until you reach that step in

the Wizard. Cables are connected to the SK 720 with the signal wire on the top (closest to the SK 720 label), positive in the middle

and ground on the bottom. On electric helis, the SK 720 is powered via the ESC. Nitro helis require the SK 720 to be powered by a

battery or BEC connected to any open port from TAIL to IO-C on the SK 720.

NOTE: Do not connect a battery or BEC to the IO-D/E or EX-LED ports.

The SK 720’s servo bus has 10 ports on the side of the unit. The table below outlines the abbreviations and names for each port.

Port Full Name

EX-LED External LED

IO-D/E Input/Output D/E

IO-C Input/Output C

IO-B Input/Output B

IO-A(T)

Input/Output A

/Throttle

SW-A Swash - Aft

SW-L Swash - Left

SW-R Swash - Right

SW-C Swash - Centre

Tail Tail


Connecting Using a 3-Point Swashplate

The diagrams below outline the servo connections to the SK 720 using 3- and 4-point swashplates. When using a three point

swashplate, you can mount the centre servo in front or behind the left and right servos

Figure 3 - Connecting the SK 720 to a 3-point swashplate, with the centre servo mounted aft

.


Connecting Using a 4-Point Swashplate

When using a four point swashplate, the centre servo gets mounted at the front of the heli, and the aft servo is mounted at the

back.

Figure 4 - Connecting the SK 720 to a 4-point swashplate


Your SK 720 can be used with Spektrum, JR, Futaba SBUS and traditional receivers. Satellite receivers are connected to the SAT RX

ports at the side of the SK 720. Figure 5 - Connecting the SK 720 to two satellite receivers

Using two Sat RXs is not necessary, though we recommend using a second satellite for larger helicopters. If you use a second Sat RX,

make sure that the antennae point in different directions to the other RX to improve signal diversity.


Spektrum/JR Sats are the default setting for receivers in the SK 720’s interface. Newer Spektrum TXs (DX7se and newer) use 2048

resolution, older (DX-7, DX-6 and older) use 1024.

Figure 6 - Spektrum/JR Sats can be set to 2048 or 1024 resolution


SBUS receivers are also connected to the SK 720 via the SAT RX port at the side of the unit using the SK-SB1 SBUS adapter.

If you are running servos directly from your SBUS receiver, run a power-only jumper cable (red and black wires only) to your receiver

along with the SBUS adapter. Power can be provided from an open port on the SK 720 or a BEC. This will provide enough power for

the receiver and servos.

NOTE: On SK720BE gyros, connect Futaba SBUS receivers directly to IO-B using a simple 3-wire jumper cable running from the SBUS

connector on your receiver. You do not need to use an SBUS adapter on SK720BE gyros.

Figure 7 - Connecting the SK 720 to an SBUS receiver


By default, the receiver in the SK 720’s software is set to Spektrum/JR - make sure to specify Futaba SBUS in the Control Tab of the

SK 720’s software. Figure 8 (below) demonstrates.

Figure 8 - Setting the receiver type to Futaba SBUS


PPM Receivers are connected to the SK 720 via the IO/B port. If you are using a PPM Receiver, make sure to specify that type of RX

in the SK 720 software.

Figure 9 - Connecting a PPM RX to the SK 720


By default, the receiver in the SK 720’s software is set to Spektrum/JR - make sure to specify PPM Receivers in the Control Tab of the

SK 720’s software. Figure 10 (below) demonstrates.

Figure 10 - Setting the receiver type to PPM


Traditional receivers are connected to the EX-LED and I/O ports using two jumper cables and the SK-CBL Traditional RX cable kit.

Note that the ESC or throttle servo is connected directly to the RX rather than the IO A/T port.

Figure 11 - Connecting the SK 720 to a traditional receiver


The diagram below displays the pin placement of the SK-CBL on the SK-720. RPM sensors are connected to the IO-C port regardless

of the SK 720’s setup. As a result, RPM sensors cannot be used along with a Traditional RX setup.

Figure 12 - SK-CBL placement on the SK 720


Be sure to specify ‘Traditional Receiver’ in the SK 720’s software when using a traditional receiver.

Figure 13 – Setting the receiver type to Traditional Receiver


Mounting the SK 720

You can mount the SK 720 in a variety of orientations. There are only two requirements for mounting the SK 720:

1. The unit’s label must face up or down

2. The unit must be mounted with its edges square to the helicopter’s frame.

Below is a diagram outlining the possible orientations of the SK 720. Figure 14 - Possible mounting orientations of the SK 720

The SK-720 must be mounted in any of the orientations shown above. Mounting in any other orientation will cause an immediate

tipover if you try to fly your heli.


The alignment of your SK 720 is very important. If your SK 720 is even a few degrees out of alignment problems can occur with

tuning the unit. A few degrees of misalignment are measured as a difference of over 2mm or 1/16” between the two ends of the

unit compared to the helicopter’s frame. Handling and control issues are often the result of improper alignment, so make sure that

all the SK 720s edges are 90° to the helicopter’s frame. Proper alignment is shown below.

Figure 15 - Proper alignment of the SK 720


The SK 720 can also be mounted in a variety of different locations on your helicopter. Ideally the SK 720 is mounted at or near the

heli’s centre of gravity for the lowest possible vibrations and best performance. However, you can mount your SK 720 away from

the centre of gravity as long as the orientation requirements are met.

Figure 16 - Mounting the SK 720 away from the helicopter's centre of gravity.

For normal flight, the SK 720 is not sensitive to vibrations. However, the high vibrations that can occur in the course of a heli’s flight

can negatively affect the Self Levelling and logging features. To minimize the vibrations transferred to the SK 720, use the anti-

vibration kit included with your SK 720.


Figure 17 - The SK 720 mounted to the SK-PL1 Anti-Vibration Kit

The vibration kit uses the thin foam between the metal plate and the SK 720, and the thick foam in between the metal plate and

your helicopter. Cutting the thick foam pad in half like the image above gives the best results.

In the case of excessively high vibrations, two metal plates glued together will provide a greater buffer between the SK 720 and your

helicopter. To correctly bond two plates together, slightly scuff the plates and use CA glue. Figure 18 - The SK 720 and SK PL1 using two metal plates


The SK 720 should never come into contact with the helicopter’s frame – this will transfer vibrations from the helicopter directly to

the SK 720. The SK 720 can be loosely tied down with a Velcro (or similar) strap. Tightly strapping the SK 720 will, however, transfer

the vibrations from the helicopter to the SK 720.

Figure 19 - Incorrect mounting of the SK 720, with the unit directly contacting the helicopter's frame

Figure 20 - Correct mounting of the SK-720, using the included anti-vibration kit


The last inch (2.5cm) of wires leading into the SK 720 should not be tied tightly. This will also lead to excessive vibrations.

Figure 21 – Tightly bound (incorrect) cables leading to the SK-720

Figure 22 - Loose (correct) cables leading to the SK-720

If you’re running the SK 720 on a helicopter with a rotor diameter over 1100mm (i.e. a 550) or any nitro heli, you should use the SK

720 in conjunction with the Power Bus. The power bus will isolate the SK 720 from the vibrations carried by heavier wiring in large

and nitro helis, and is designed to handle the high levels of electrical current from the high voltage servos typically used in larger

helis.


Connecting and Mounting the Power Bus

The Power Bus connects straight to a 2 cell (7.4V) battery or BEC, and is designed to handle 20 Amps of continuous current. It can

run high voltage, low voltage, and a combination of high and low voltage servos from a single power supply. The Power Bus is also

handy for cleaning up the cables connecting to the SK 720 and reducing vibrations that can result from having cables tightly

connected to the SK 720.

When running high voltage servos only, you need to bridge the PWR-LV and –HV ports with the included jumper cable. The low

voltage rail is only powered when connected to the HV rail via jumper or BEC.

Figure 23 - Power Bus and SK 720 with high voltage servos


The cables connecting BUS-B and BUS-C to the SK 720 are connected across the top row of pins, as shown below.

Figure 24 - Pin connections between the SK 720 and Power Bus


If you are using a combination of high and low voltage servos, connect the low voltage servos to the LV rail and bridge the LV and HV

rails using a BEC. Be sure to set your BEC’s output to your servo’s specified voltage. Figure 25 - Connecting both high and low voltage servos to the Power Bus


Receivers use the same connections to the SK 720 whether you use the Power Bus or not. However, using traditional or PPM

receivers limits the number of output channels available on the SK 720.

PPM receivers can be connected to the IO-B port on the Power Bus, or, if you don’t need the aux. (IO) ports, to IO-B on the SK 720.

However, BUS-C cannot be used when connecting a PPM receiver directly to the SK 720.

Since traditional receivers use the EX-LED port and all of the IO- ports, the aux. ports on the Power Bus are not available. RPM

sensors are also not available when using a traditional receiver, as the IO-C port normally reserved for an RPM sensor is used for the

receiver’s rudder input.

Figure 26 - Connecting the SK 720 and Power Bus to a traditional receiver


The IO-C port on the SK 720 is reserved for RPM sensors in all connection options, except when using a traditional receiver. When

using the Power Bus, IO-C is left open on the SK 720 for the use of an RPM sensor.

Figure 27 - Connecting an RPM sensor to the SK 720

The SK 720 is compatible with all phase and crankcase sensors as of the release of this manual, including Hyperion and Eagle Tree

sensors. However, if you use an Eagle Tree sensor you must swap the red and black wires.

Most sensors will be damaged by voltage higher than 5.5V. If you are using HV servos on your heli, the SK 720 will output the higher

voltage to the RPM sensor. Using a step-down to the sensor will be necessary if you use HV servos.


Proper Servo Alignment The alignment of your servos is key to the proper handling of your heli with the SK 720. However, this is a simple as setting your

servo trims within the SK 720’s software. With both sticks set to their centres, adjust the servo trims so your servos are as close as

possible to 90° to their linkages, as shown below.

Figure 28 - Servos trimmed 90° to linkages.


Make sure to adjust the trims for the swashplate servos and the tail servo. Your swashplate servo trims are adjusted in the Swash

Servos tab in the SK 720’s interface.

Figure 29 - Trimming the swashplate servos in the SK 720's software.


The tail servo is trimmed in the Tail Servo tab. The tail servo can be trimmed by adjusting the value in the box itself, or using the

‘Setup Servo with Rudder Stick’ button.

Figure 30 - Trimming the tail servo in the SK 720s software.

Once you’ve set the servo trims in the SK 720’s software, mechanically adjust the swashplate linkages to level the swashplate, and

the tail linkage to give 0° of tail pitch at centre stick.


Checking Pitch and Phasing If your SK 720 equipped heli seems like it’s not handling properly, it’s important to check the mechanical condition of your heli as

well as the SK 720. Issues with blade pitch, phasing, and tracking can often lead to handling issues but often are relatively easy to fix.

There are a few factors to consider when checking and tuning your blade pitch and phasing:

• Whether your blades are centred at 0 collective pitch

• Your minimum and maximum collective pitch

• Your cyclic pitch

• Proper blade phasing

• Blade tracking

Setting Collective Pitch

To check if your blades are centred, set your collective stick to 0% and mechanically adjust each blade using a pitch gauge until it

reads 0°. Figure 31 - Checking for zero pitch.


To set your minimum and maximum collective pitch, measure the pitch values with the collective stick at 0 and 100. Adjust the

collective pitch range in the SK 720’s software until you reach your desired collective pitch.

Figure 32 - Measuring minimum collective pitch, with the collective stick at 0.

Figure 33 - Measuring maximum collective pitch, with the collective stick at 100.


Typically +/- 12 degrees of collective pitch is normal, but you can set your collective pitch according to your own preference. You

can adjust the collective pitch range using the Collective Pitch mixing field in the Swashplate tab, as shown below.

Figure 34 - Adjusting the collective pitch in the SK 720's software.


Setting Cyclic Pitch

The first step of setting the cyclic pitch is to hold one of your main blades over the tail boom, shown in the photo below. Figure 35 - Aligning a blade over the tail boom.

Next, hold your blades at max cyclic pitch using either the Swash and Cyclic Setup Wizard or the “Hold Maximum Cyclic” option in

the Utility menu. Using the pitch gauge, measure the maximum cyclic pitch. Adjust the Elevator and Aileron mixing fields until you

reach 10° of cyclic pitch.

Figure 36 - Adjusting the cyclic pitch range in the SK 720's software.


Checking your blade phasing, you’ll again hold one blade over the boom. With your servos powered and your transmitter on, the

blade shouldn’t move at all when you give elevator inputs. Correct the phasing by making sure that the swashplate linkages are

parallel to your heli’s drive shaft when looking straight down on top of the rotorhead.

If your heli has a multi-bladed scale head, you can adjust the phasing using the Phase Trim settings in the Swashplate tab.

Figure 37 - Adjusting phase trim in the SK 720's software.

To adjust the tracking on your main rotor, measure the pitch on each blade with the collective stick at zero. Pick one blade as your

master blade, and adjust the other blade or blades to the same pitch as the master.


Final Checks: Observe these precautions before every flight

1) Check to ensure that the Indicator LED is solid green (not flashing).

2) Check that positive collective increases blade pitch.

3) Check that right aileron stick tilts the swash for a right roll.

4) Check that nose-up elevator stick tilts the swash for nose-up.

5) Pick up the helicopter, and tilt it nose down and to the right. The swashplate should tilt back and left.

6) Rotate the heli’s nose to the right 90 degrees. The tail blades should move to counter-act the motion.

7) Always takeoff, land and fly at a safe distance from yourself and bystanders.

WARNING: Remember to return your throttle stick to the idle position before releasing throttle hold.

NOTE: In flight mode, the swashplate will tilt slightly forward at full positive collective to compensate for tail-drag. Likewise, it

will tilt slightly back at full negative collective.

Flight with the SK 720

In flight mode, the swashplate will not respond to the controls directly. Its action will be similar to a heading-hold tail gyro. After it

has been static for a few seconds, it will level the swash during spool up to ensure a stable take off.

For most helis, we recommend that you start with 50% cyclic gain, and 50% tail gain. For small helis, you may want to start with 40%

cyclic gain, and 30% tail gain.

Don't move the cyclic stick until the heli is light on its skids to prevent confusing the gyro before the helicopter can respond to the

gyro’s control inputs. Lift the helicopter off into a hover and try some small elevator and aileron inputs. If the helicopter doesn’t

hold well in pitch or roll or “slides” to the side, turn the Cyclic gain up a small amount. If the helicopter wobbles while hovering, turn

the Cyclic gain down. If the cyclic control is too slow for you, increase the control rates for cyclic, and if it’s too fast, lower the control

rates.


Then try some sharp rudder inputs. Incrementally adjust the tail gain to the maximum value possible that doesn’t result in any

oscillation during hover or after sharp stick motions.

When you land your helicopter, always wait at least 5 seconds after the rotor stops before spooling up again. This lets the gyro save

any changes to self-tuning, and detect that the helicopter is spooling up for another take off.


Self Levelling with the SK 720

Your SK 720 features a self-levelling function with four different modes: Always On, Centre Stick, Always On & Inverted, and Centre

Stick & Inverted.

Always On: This mode will constantly try to level your heli, making it fly like a coaxial helicopter. 3D and other acrobatic manoeuvres

are essentially impossible in this mode.

Centre Stick: Your heli will fly normally in this mode until you let go of the Cyclic control stick, at which point your heli will self-level.

This mode allows a full range of manoeuvres. The Centre Stick setting is commonly used as a “bailout” or “rescue” function.

Always On & Inverted: This mode will constantly try to level your heli, both upright and inverted. It will try to level your heli upright

until it reaches 60°of inverted – at this point it will try to level your heli upside down.

Centre Stick & Inverted: This mode will allow you to fly normally, upright and inverted, until you centre the Cyclic stick. Like the

Always On & Inverted mode, it will level your heli upside down once it reaches 60° of inverted.

The percentage you set your Self Levelling to will set how fast your heli returns to level. For example, setting your self level to 80%

and control rates to 300 deg/s will level the heli at 240 deg/s. When using self levelling as a bailout feature, you should set your self

levelling percentage between 80-100%.

You can set two banks of self-level settings (one on each cyclic bank). By setting one bank with self leveling off and another to

Always On, and flying on the “off” bank, switching to the “Always On” bank will act as a bailout function.


Warranty and Technical Support

Skookum Robotics Ltd warrants this product against any defects in materials or workmanship for a period of 90 days from the

purchase date. This warranty is limited to the original purchaser. In the event of a malfunction, Skookum Robotics will repair or

replace the product to meet its standard operating condition. This warranty does not apply in cases where the product has been

overheated, electrically shorted, subject to crash damage, otherwise abused, or had unauthorized repair attempts.

UNDER NO CIRCUMSTANCES DOES SKOOKUM ROBOTICS ACCEPT LIABILITY FOR INCIDENTAL DAMAGE OR INJURIES RESULTING

FROM THE OPERATION OF THE SK 720 OR OTHER PRODUCTS.

Skookum Robotics will provide customers with technical assistance by email free of charge. If a gyro’s serviceability is in question

following a crash, we will check it over for only the cost of postage. If the unit has malfunctioned and the 90-day warranty period has

expired, we will attempt repair, and discuss the cost of possible repairs with the owner, again for only the cost of postage.

If you wish to return the gyro unit or related product, please write “WARRANTY RETURN” clearly on the shipping box, and mail it to

the address given below.

NOTE:

- Do not ship your gyro to our PO box via courier. Courier shipments will be returned to the sender at the sender’s expense.

- Packages subject to customs charges incurred due to no clear “WARRANTY RETURN” marking on the box/envelope will be

returned to the sender at the sender’s expense.

Manufactured in Canada by Skookum Robotics, Ltd

Email: [email protected]

Website: www.skookumrobotics.com

Return Mail: PO Box 46912 Stn D

Vancouver, BC

V6J 5M4 Canada

setup guide sk 720 flybarless system sk-pb1, sk-pb2 power bus · 2017. 12. 11. · by default, the...

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