Smart Avionics PB-4 User manual

PB-4 Propeller & Rotor Balancer
Hardware Manual
Smart Avionics Ltd.
16/04/2019www.smartavionics.comRevision: 1.6

PB-4 Propeller & Rotor Balancer: Hardware Manual
Revision: 1.6
Publication date 16/04/2019
Copyright © 2003-2019 Smart Avionics Ltd.
Android is a trademark of Google Inc.
iOS is a trademark of Apple Inc.
Dropbox is a trademark of Dropbox inc.
Gyroplane photographs courtesy of Mike Goodrich and Jerôme Prompsy.

Table of Contents
1. Introduction ................................................................................................... 1
1.1. Balancing system overview ............................................................... 1
1.1.1. Wi-Fi network components ..................................................... 1
1.2. Accessing the PB-4 user interface .................................................... 3
1.2.1. Accessing the PB-4 user interface (AP mode) ...................... 3
1.2.2. Accessing the PB-4 user interface (STA mode) .................... 3
1.3. Batteries ............................................................................................. 4
1.4. PB-4 panel .......................................................................................... 5
1.5. Environmental limits .......................................................................... 7
1.6. Operator warning ............................................................................... 7
2. Preparing for Propeller Balancing ................................................................ 9
2.1. Additional items required .................................................................. 9
2.2. Positioning the aircraft ...................................................................... 9
2.3. Mounting the accelerometer ........................................................... 10
2.4. Mounting the tacho sensor ............................................................. 12
2.5. Attaching the reflective tape ........................................................... 14
2.6. Attaching the cables ........................................................................ 15
2.7. Positioning the PB-4 ........................................................................ 16
3. Preparing for Rotor Balancing ................................................................... 17
3.1. Mounting the sensors ...................................................................... 17
3.2. Positioning the PB-4 ........................................................................ 21
3.3. Offline capture button ..................................................................... 22
4. The PB-4 User Interface ............................................................................. 23
4.1. Getting started with the browser based user interface ................. 23
5. Upgrading the PB-4's Firmware ................................................................. 25
5.1. Upgrading the UI firmware .............................................................. 25
5.2. Upgrading the CPU firmware .......................................................... 25
5.3. Upgrading the Wi-Fi firmware ......................................................... 26
A. Battery Charging & Replacement .............................................................. 27
A.1. Replacing the RTC battery .............................................................. 27
B. Specifications ............................................................................................. 29
B.1. Main unit .......................................................................................... 29
B.2. Accelerometer ................................................................................. 29
B.3. Tachometer ...................................................................................... 29
C. EMC Compliance & Safety Information .................................................... 31
D. CE Declaration of Conformity .................................................................... 33
Index ................................................................................................................ 35
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List of Figures
1.1. Wi-Fi roles when PB-4 is in AP mode ....................................................... 2
1.2. Wi-Fi roles when PB-4 is in STA mode ..................................................... 2
1.3. PB-4 panel .................................................................................................. 5
2.1. Accelerometer axes and orientation ...................................................... 10
2.2. Accelerometer mounted on a Rotax 912 gearbox ................................ 11
2.3. Tacho sensor with flexible mounting plate ............................................ 12
2.4. Tacho sensor mounted on cowling ........................................................ 13
2.5. Tacho sensor angle of incidence ........................................................... 14
2.6. Cable taping ............................................................................................. 15
3.1. Standard sensor orientation (top view) ................................................. 18
3.2. Sensors mounted on an ELA rotor head (top view) .............................. 19
3.3. Sensors mounted on an ELA rotor head (side view) ............................. 20
3.4. Sensors mounted on an ELA rotor head (bottom view) ........................ 20
3.5. Sensors mounted on a Magni prerotator drive ...................................... 21
4.1. Initial screen ............................................................................................ 23
A.1. Locating the PB-4 board securing screws ............................................. 28
A.2. Correct orientation of RTC battery ......................................................... 28
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Chapter 1. Introduction
This manual describes the hardware of the Smart Avionics PB-4 product and
how to prepare for balancing a propeller or rotor using the PB-4. The balancing
procedures and the features of the PB-4 software are covered in the user
interface manual (pb4_ui_manual.pdf).
1.1. Balancing system overview
The PB-4 balancing system has these main components:
This is mounted near the hub of the propeller/rotor to
detect the vibration due to imbalance.
Accelerometer
A strip of reflective tape is attached to one propeller/rotor
blade and an optical sensor detects the tape as it passes
Optical
tachometer
and generates the tachometer signal required by the
balancer.
This processes the vibration signal and sends the resulting
data over a Wi-Fi network to be displayed on the user
interface (UI) device.
Digital processor
(CPU)
This provides the means whereby the user can view the
results and interact with the PB-4 using a standard web
User interface
device
browser. The PB-4 may also be used with the Propeller
Balancer Android app.
The PB-4 uses Wi-Fi to communicate with the user interface device which can
be any computer that supports a modern browser and Wi-Fi. Obviously, the
most suitable devices for use in aircraft are lightweight tablets. A 7" format
tablet is a good choice for use while balancing as it is not too bulky but still
has reasonable screen resolution. Later, you can look at the results on a device
with a bigger screen, e.g. a laptop computer. The following text simply calls
the user interface device a tablet.
1.1.1. Wi-Fi network components
The PB-4 uses a Wi-Fi network to communicate. Most commonly, a Wi-Fi
network consists of an access point and one or more stations . The network
traffic to and from the stations is routed through the access point. The PB-4
can operate as either a Wi-Fi station or as a Wi-Fi access point depending on
where you are located at the time.
1.1.1.1. PB-4 is the Access Point
When you are at the airfield doing the balancing, you would not normally have
an access point available. Fortunately, the PB-4 can be the access point (as
well as being a balancer). By starting the PB-4 in AP mode, it will be an access
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point and the tablet will be able to communicate with it directly as shown
below. Note that unless the tablet has some other means of accessing the
internet, it will only be able to talk to the PB-4 in this configuration.
SSID: PB4- XX
PB-4
AP MODE
TABLET
WEB BROWSER
HOST ADDRESS
ALWAYS 172.21.21.1
PB-4 & UI device
communicate via
PB-4's built in AP
Fig 1.1. Wi-Fi roles when PB-4 is in AP mode
1.1.1.2. PB-4 is a station
When you are back indoors, your tablet will most likely be already configured
to use an existing access point at that location. The PB-4 can be started as a
station (STA mode) and it will then use the same access point as the tablet
so they will be able to communicate. In this configuration, your tablet will be
able to access the network (internet, printers, etc.) as normal.
ACCESS
POINT
SSID: YOUR WIFI NAME
PB-4
STA MODE
TABLET
WEB BROWSER
HOST ADDRESS ASSIGNED
BY ACCESS POINT
PB-4 & UI device
communicate
via separate AP
Fig 1.2. Wi-Fi roles when PB-4 is in STA mode
For the PB-4 to be able to talk to the access point, it needs to know the access
point's SSID (Wi-Fi network name) and password. The PB-4 supports Wi-Fi
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Wi-Fi network components

Protected Setup (WPS) which makes setting up the access point credentials
easy. The SSID and password may also be entered into the PB-4 manually if
required.
Note
One way of remembering which mode you need to use is that when
you are "at the AirPort" use AP mode and when you "STAy at home",
use STA mode!
1.2. Accessing the PB-4 user interface
Safari users please note that the PB-4 is not compatible with Safari's “Private
Mode”.
Accessing the PB-4 user interface from your tablet's browser requires the
PB-4 and the tablet to be using the same Wi-Fi network.
1.2.1. Accessing the PB-4 user interface (AP mode)
When the PB-4 is in AP mode, the Wi-Fi network name (SSID) will be PB4-XX
where XX are two letters/digits. You will need to tell your tablet to use that
Wi-Fi network (via its Wi-Fi configuration). At the airfield, the tablet will probably
use the PB-4 Wi-Fi automatically because your normal Wi-Fi is not available.
If not, you will have to tell the tablet to use the PB-4 Wi-Fi manually.
Once the tablet is using the PB-4 network, you can load the user interface
page into the browser. If your tablet supports MDNS, you can simply use
pb4.local as the host name in the browser. Apple devices (mac/ipad/iphone)
and most Linux systems have MDNS, most Windows systems do not. If not,
use the IP address 172.21.21.1. Having accessed the PB-4 user interface
page, just add a bookmark for that page in your browser called something like
"PB-4 AP Mode (at the airfield)".
1.2.2. Accessing the PB-4 user interface (STA mode)
When the PB-4 is in STA mode, the Wi-Fi network name (SSID) will be whatever
you normally use at the current location. The PB-4 will need to be taught that
SSID and the associated password. The PB-4 supports WPS for automatically
obtaining the SSID and password from the access point which is quick and
easy if the access point also supports this feature. Alternatively, you can
manually enter the credentials by starting the PB-4 in AP mode, loading the
user interface into your browser (as described above), connecting to the PB-4
(click on red button) and then going to Menu / Options / PB-4 Configuration
/ Set Access Point Details.
Once the PB-4 is able to connect to the local network, you can load the user
interface page into the tablet's browser. Again, if MDNS is supported by the
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Accessing the PB-4 user interface

tablet, the host name pb4.local can be used. Otherwise, you need to find out
the IP address that has been assigned to the PB-4 by the access point. Follow
these steps:
1. Turn on the PB-4 in STA mode (press the on/off switch until LED 2 goes
green). When you release the switch, LED 2 will go off and then after a few
seconds will flash green slowly if the PB-4 has successfully managed to
log into the access point.
2. Turn the PB-4 off (press switch until the LEDs go out).
3. Turn the PB-4 on again but this time start it in AP mode (press on/off only
until LED 1 comes on).
4. Access the PB-4 user interface page with your browser as described in the
previous section, connect to the PB-4 (click on red button) and then go to
Menu / About. The about box will contain a line that says STA Mode IP
Address: XX.XX.XX.XX. The address that is shown is the IP address that
has been assigned to the PB-4 by the access point, note it down.
Having found out the PB-4's IP address when in STA mode, you can use that
address to access the user interface page and then add a bookmark for that
page in your browser called something like "PB-4 STA Mode (at home)".
1.3. Batteries
The PB-4 is powered by 4 x 1.2V AA NiMH rechargeable batteries. The batteries
are easily accessible via a hatch in the bottom of the PB-4 case. The PB-4
itself cannot charge the batteries, they have to be removed and charged in an
external charger. It is also possible to use non-rechargeable 1.5V AA batteries
in the PB-4.
The PB-4 also contains a CR2032 3V coin cell which provides backup power.
This battery will require replacing every now and then.
See Appendix A for more information on battery charging and replacement.
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Batteries

1.4. PB-4 panel
LED1 &
ON-OFF
SWITCH
LED2 &
JACK
SOCKET TACHO ACCEL 1 ACCEL 2
Fig 1.3. PB-4 panel
The panel contains:
The on-off switch is a push button. When turning the PB-4 on,
how long you hold the button pressed affects the Wi-Fi mode
On-off
switch
used. Outdoors, when balancing, a short press is required to
start the PB-4 in AP mode.
Press the on-off switch until the LEDs light
(about ½ second), then release switch. After a
Turn on PB-4
(AP mode)
few seconds, LED 2 should slowly flash green
to show that it is in AP mode waiting for the
tablet to connect.
Press and hold the on-off switch until LED 2
changes from green to red (about 1 ½ seconds).
Turn on PB-4
(STA mode)
On release, LED 2 will go off until the PB-4 has
finished initialising. If the PB-4 has the right
credentials for the access point, LED 2 should
now be slowly flashing red to show that it is in
STA mode waiting for the tablet to connect.
Press and hold the on-off switch until LED 1
flashes quickly (about 5 seconds). The PB-4
Turn on PB-4
(WPS mode)
has entered WPS mode. Press the WPS (QPS)
button on the access point and the PB-4 should
receive the credentials from the access point.
If successful, the PB-4 will restart in STA mode
(LED 2 slowly flashing red). Otherwise, the PB-4
will restart in AP mode and LED 2 will be slowly
flashing green.
Press and hold the on-off switch until LEDs go
off (about ½ second).
Turn off PB-4
With the PB-4 turned on, press and hold the
on-off switch. LED 1 will go out after ½ second
Factory reset
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PB-4 panel

but keep pressing until LED 1 becomes red
again (about 10 seconds). It will then reset all
configuration values to their defaults. This will
not lose any job data stored on the PB-4.
The main purpose of LED 1 is to indicate whether the PB-4 is
receiving a tacho signal.
LED 1
PB-4 is switched off.Off
RPM is detected.Green
(continuous)
RPM is not detected.Red
(continuous)
WPS mode entered.Red (flashing)
The main purpose of LED 2 is to indicate the current Wi-Fi mode
and whether the user interface is connected to the PB-4.
LED 2
PB-4 is switched off or Wi-Fi is still being
initialised.
Off
AP mode - user interface not connected.Green (slow
flash)
AP mode - user interface is connected and
receiving data.
Green
(continuous)
STA mode - user interface not connected.Red (slow
flash)
STA mode - user interface is connected and
receiving data.
Red
(continuous)
One or two Smart Avionics 2-axis accelerometers may be
connected using 4-wire cables. If you are only using 1
accelerometer, always connect it to Accel 1.
Accel 1 &
accel 2
connectors
Connects (using a 3-wire cable) to the Smart Avionics Red LED
Tacho Sensor that is measuring the propeller/rotor RPM. This
is tacho channel A.
Tacho
connector
A 3.5mm jack socket that is used to connect a pilot operated
push switch that triggers data capture. This allows data to be
captured in flight without the tablet needing to be present.
Jack socket
The socket connections are:
• Barrel - ground.
•Ring - tacho channel B input (contact Smart Avionics for details
if you wish to use this).
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PB-4 panel

• Tip - capture switch input (connect to ground to capture).
1.5. Environmental limits
Please operate the PB-4 within the following environmental limits:
-20° to +45° C (-4° to 113° F)Temperature
5% to 95% non-condensingRelative humidity
1.6. Operator warning
Warning
The PB-4 contains a microwave transmitter (the Wi-Fi module). To
be compliant with the FCC RF radiation exposure limits, the PB-4
should not be located closer than 20cm from a human body while
operating.
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Environmental limits

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Chapter 2. Preparing for Propeller
Balancing
Caution
Propellers can kill.
Make sure that the ignition is switched off before touching the
propeller.
Always assume that the engine could fire when the propeller is
being moved.
Make sure that the aircraft is securely chocked or tied down while
carrying out the balancing process.
2.1. Additional items required
To carry out the balancing process, you will need the following items in addition
to the balancer kit:
• Balance weights (typically AN970 washers) and a means of securely
attaching them to the spinner backplate.
• If necessary, a bracket for mounting the accelerometer onto the front of
the engine (optional, depending on engine type and installation details). An
M6 screw and washer are supplied which can be used to attach the
accelerometer to the back of a Rotax 4-stroke gearbox if the vacuum pump
option is not fitted.
2.2. Positioning the aircraft
The following points should be observed regarding positioning the aircraft for
a propeller balancing session:
1. The position must be safe for ground running of the engine. Typically, the
engine will need to be run at cruise RPM and the aircraft should be braked
and chocked and, if necessary, tied down.
2. If the sun is low on the horizon it is best if the sun does not lie within the
arc of the propeller when viewed from the location of the tacho sensor.
3. If there is any wind, point the aircraft as close into wind as possible while
observing point 2 above. If the wind is greater than 10kts or gusty it will be
difficult to obtain a really good balance.
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2.3. Mounting the accelerometer
Remove sufficient cowlings to gain access to the front of the engine. Mount
the accelerometer (40mm square with a 6mm hole through the middle) as
near to the front of the engine as possible with the accelerometer's sensing
axis pointing directly at the propeller's centre line.
The accelerometer's X axis coincides with the direction of the sensor's cable
socket and its Y axis is at 90° to the direction of the cable socket.
X Axis
Y Axis
Fig 2.1. Accelerometer axes and orientation
Important
The sensing axis used must intersect the axis of rotation of the
propeller.
Remember to configure the job to use the correct axis.
Note that the accelerometer does not have to be directly above the propeller's
axis of rotation. However, to get the best results you should not mount the
accelerometer such that the sensing axis is parallel with the engine's cylinders.
On a Rotax 4-stroke engine that doesn't have a vacuum pump attached, the
best place to mount the accelerometer is on the rear of the gearbox using one
of the available tapped holes and the supplied M6 screw and washer.
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Mounting the accelerometer

Fig 2.2. Accelerometer mounted on a Rotax 912 gearbox
If the accelerometer cannot be bolted directly to the engine, some form of
bracket will be required. Obviously, the details of this are engine specific but
it could be as simple as a strip of metal with a hole drilled at each end. If a
bracket is used, it must be sufficiently stiff to ensure that the accelerometer
does not move with respect to the engine.
However the accelerometer is mounted, it must not be subjected to excessive
temperatures. The temperature of the sensor should not exceed 85° C. If
necessary, thermally insulating material can be sandwiched between the
accelerometer and the engine (or bracket) to reduce the amount of heat
conducted to the accelerometer. If the surrounding area will be very hot, the
accelerometer could be wrapped in thermally insulating material (once the
cable has been attached).
Important
The accelerometer is robust but may be damaged if dropped on a
hard surface.
It is preferable to refit the engine cowling to minimise the turbulence generated
by the airflow from the propeller. For some aircraft, the cowling will have to
be refitted to provide a suitable mounting position for the optical sensor.
However, if the balance weights are to be added to the rear of the spinner
backplate, it may pay to leave the cowling off (if possible) during the balancing
process so that it is easier to gain access to the weights. Once the balancing
has been completed, the cowling could be replaced and a final reading taken
to determine the level of vibration achieved.
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Mounting the accelerometer

2.4. Mounting the tacho sensor
Owing to the variation in aircraft cowling shapes and sizes, only generic
instructions can be provided here. You may find that a little experimentation
is required to obtain the best results.
The tacho sensor is drilled for a 6mm fastener and so it may be securely bolted
to the airframe using a suitable bracket. With an adequately strong bracket,
it would be safe for the aircraft to be flown with the sensor attached in this
way (assuming no other safety issues arise).
For ground use only, a flexible plastic mounting plate is provided. The sensor
is bolted to the plate and then the plate may be taped to the aircraft cowling.
The supplied soft washer should be placed between the tacho sensor and the
mounting plate to increase the friction as this will reduce the fastener torque
required.
Fig 2.3. Tacho sensor with flexible mounting plate
Caution
This method of mounting the tacho sensor on the cowling is
perfectly adequate when the aircraft is stationary on the ground.
Under no circumstances should the aircraft be flown with the tacho
sensor attached using the flexible mounting plate.
Caution
If the propeller is a pusher, i.e. the cowling is in front of the propeller
rather than behind, extra care should be taken to ensure that the
tacho sensor cannot become detached from the cowling and hit
the propeller blades. As a minimum, tape the accelerometer cable
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Mounting the tacho sensor

to the cowling so that it will restrain the tacho sensor in the event
of it becoming detached from the cowling. If you have any doubt
as to the security of the tacho sensor, don't risk destroying it and
the propeller.
Position the tacho sensor such that the sensor block is pointing towards the
propeller. If the sensor's orientation is correct, the blades will sweep across
the sensor block as the propeller rotates. The distance from the front of the
sensor to the propeller should be in the range 5-75cm.
Fig 2.4. Tacho sensor mounted on cowling
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Mounting the tacho sensor

Fig 2.4 shows the tacho sensor mounted an aircraft cowling.
Important
To detect the propeller RPM reliably when the propeller blades are
reflective, the tacho sensor should be positioned such that the angle
of the LED beam is not normal to the faces of the propeller blade.
Rotate the tacho sensor so that it is approximately 30° from the
normal (either in front of or behind the normal). Fig 2.5 illustrates
this.
Normal
TACHO
SENSOR
Approx 30 degrees
angle of incidence
(from normal)
Fig 2.5. Tacho sensor angle of incidence
If the angle is too small, the tacho sensor will tend to detect the
other blades (especially if they are highly reflective) and the RPM
will appear erratically too high. If the angle is too large, the blade
with the reflective tape will not be reliably detected and the RPM
will appear zero or erratically too low.
2.5. Attaching the reflective tape
With the engine ignition switched off, rotate the propeller so that one blade
lies directly on the sensing axis of the tacho sensor. Make sure that the area
on the back of the blade where the tape is going to be attached is clean. Apply
a strip of 25mm wide masking tape to the back of the propeller at the point
that the red beam will hit the blade. Wrap the tape a short distance around
the leading edge of the blade but don't wrap it around the trailing edge.
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Attaching the reflective tape