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SmartDrive
Motor
Converting a Fisher & Paykel
Washing Machine Motor
by
Nenad
Stojadinovic
Recycled smart drive washing machine motors have been used in
countless projects. They can be found in wind turbines, water turbines,
and every other type of generator imaginable. This article takes a radical
new direction and uses a Fisher & Paykel SmartDrive as . . . a motor.
W
hy would you want to use a SmartDrive as a ing to build a big white box into every project can put a
motor? Possibly you drooled at the possibilities cramp on any young tech’s style.
presented by the pan-cake motor used in our eBike
Those clever Kiwis
article featured in the November 2011 issue.
You have to hand it to the Kiwis: the Fisher & Paykel
But that motor has a maximum power output of a few
hundred watts, depending on how its controller is pro- “SmartDrive” is certainly a clever device. In an era where
washing machines were powered by conventional single
grammed.
What if you could use a recycled motor of the same gen- phase induction motors driving a gearbox, the introduction
eral configuration but with a power output which might of a microprocessor-controlled, direct drive motor was a
great innovation. It has been proved in untold numbers of
peak at 1kW or more?
The SmartDrive used in Fisher & Paykel washing ma- washing machines over the years and there are now recychines is just such a motor. In fact, it is the only such cling centres full of machines that have been scrapped but
motor which you can pick up either free from roadside still having a perfectly serviceable motor.
The mountains of SmartDrives laying around have not
clean-ups (ie, in discarded washing machines) or cheaply
been missed by the tech community and there are countless
from recycling centres.
Of course, the SmartDrive is already a motor. What’s the versions of every type of generator using the SmartDrive
point in converting a motor into a motor? Well, apart from its as a core.
To our knowledge though, there have not been any devicpotentially high power output, this motor can be smoothly
es featuring the SmartDrive as a motor. This is no surprise;
controlled over a very wide range, up to 1200 RPM.
at the first sight of a motor with three
In Fisher & Paykel washing machines,
fat power cables and no less than five
the SmartDrive dispenses with a gearCoil Input Hall Outputs
control leads, you quickly realise that
box and runs both the wash/rinse cycles
YBG
using it in your particular application
and the spin cycles.
A+ B001
might not be a 5-minute conversion.
But aside from the fact that the SmartA+ C011
The SmartDrive can be thought of in
Drive motor runs on awkwardly high
B+ C010
two ways: as a huge stepper motor wired
voltages, it is a class of machinery that
B+ A110
in a 3-phase star configuration with a
comes perilously close to being a comC+
A100
fixed stator (the central non-rotating
puter peripheral, or at least a symbiotic
C+ B101
part) and a hub (the rotor) with embedcomponent of a computer.
ded magnets.
In this case, the computer is firmly Table 1: the six-step commutation
The stator consists of 42 poles (each a
built into a washing machine and hav- sequence with Hall Effect outputs.
14 Silicon Chip
siliconchip.com.au
The major components in a
Fisher&Paykel SmartDrive
motor. Top left is the magnet
hub, top right the stator,
centre is the drive shaft
and at the bottom are the
retaining plates and nut.
coil with a laminated steel core) and is 250mm in diameter.
much like a stepper motor (see Fig.1) and is referred to
The hub has 56 magnets embedded in plastic and with
as electronic commutation.
hidden steel laminations to complete the magnetic circuit.
Note that each winding is polarised north at one step
Or you can regard it as a variable speed, synchronous
and south at another so that a full cycle has three phases
AC motor or a 3-phase permanent magnet motor. It is also
multiplied by two polarisations which equals six steps.
known as brushless DC (or BLDC).
The drive sequence is thus called a ‘six step commutaIt is not an induction motor. Typical induction motors
tion sequence’ and is as given in Table 1 – ignore the Hall
that run on 3-phase 415VAC have no
Effect column for the moment.
permanent magnets. Instead they have
And that’s why it is very easy to use
a series electromagnets arranged in a
a SmartDrive as a generator and so very
circle, each connected to a separate
difficult to use as a motor.
phase of mains power, to produce a
In a generator, the force supplying the
rotating magnetic field. The magnetic
rotation (be it from a wind or watermill,
field then induces currents in the rotor
etc) simply swings the magnets past the
which consequently generates its own
wound coils to generate a voltage in the
magnetic field, and the interaction of
classic way which we all desperately
the magnetic fields then drags the roswotted up before the final year 12 scitor around.
ence exam.
An induction motor always has “slip”
Pick up and rectify the generated
which is the difference between the
power as necessary and you’re done.
speed of the rotating magnetic field (the
Driving the motor is a vastly more
“synchronous” speed) and the actual
complex matter of monitoring the exact
motor speed.
position of the rotor as it goes around
3-phase permanent magnet
and switching current to the approprimotors are driven by DC and are comate winding at exactly the right instant.
pletely dependent on their driver,
There are two main ways of monitorwithout which they sit there and smoke.
ing the rotor position. Small motors genThe motors have wound coils like the
erally monitor the voltage in windings
induction motor but those coils are Exploded view of the motor, from the
that are not currently energised, the idea
energised by DC from a microcontroller. F&P service manual. Most of these
being that a rotor magnet will go past
As noted above, the process is very parts can be seen in the photo above.
the winding and generate a little pulse
siliconchip.com.au
February 2012 15
Fig.1: the first steps from Table 1 starting from zero at A+, B-. Note that the relevant polarity can be seen from the position
of the alligator clips. A positive voltage makes the relevant winding a south pole, for example A+, B- makes the A winding
south and the B winding north.
of voltage that can be detected by the controller.
A bit of fancy maths and the controller will have a very
good idea of the rotor position but only once the motor
is moving. Without rotor movement there are no voltage
pulses so starting up can be a bit problematic.
Larger motors use Hall Effect sensors and these little
fellows will report the rotor position all the way down to
zero speed.
Modern sensors used in motors are minuscule surface
mount chips that output say 5V when facing a north pole
and 0V when facing south.
My wife threatened dire consequences and so I ended up
with only three complete motors, a very nice pump from
a commercial dishwasher, a wood lathe that I later turned
into a centrifuge, a refrigerated air dryer and a compressor
powered not one but two 15kW motors (don’t ask!).
On reflection, it may be easier to simply ring a washing
machine repairman and offer to buy a motor – the going
price is around $30 – or else keep an eye on the appliance
section of the classifieds.
eBay is perhaps another source but you’ll probably find
anyone who has removed a SmartDrive motor to put on
eBay knows that it is worth a few bob (eg, $50-$60!).
First catch your hare SmartDrive
The SmartDrive is classed as an “outrunner”, meaning
Having said that dumped
that the outside of the motor
washing machines are availrotates and is thus the rotor.
able in huge piles, I have to
Tipping the machine onto its
admit that I couldn’t find
side and spinning the plastic
one to scavenge and ended
rotor, you will see the washup placing a wanted ad in
ing drum rotating in unison.
the local free classifieds
The rotor has a total of 56
web site.
magnets and the magnets are
That did the trick but
contained in strips that are
I have to warn anybody
magnetised NSNS (see Fig.2).
following this path that
Having removed the rotor
one is likely to trigger an
you will see the stator which
avalanche that is not easily
is secured by four self tapstopped.
ping bolts.
It seems that everybody
If you count them, the
knows somebody who has
stator appears to consist of
junk to be gotten rid of and
42 wound coils but closer
is very happy to find someexamination shows that they
one who is happy to do it,
are really three coils that are
Fig.2: each strip consists of four magnets. You can just see
the lines between them.
especially for free.
each made up from 14 coils
16 Silicon Chip
siliconchip.com.au
EACH PHASE HAS 14 COIL WINDINGS
A1
A
A14
A2
B2
B1
B
C1
STAR
POINT
B14
C2
C14
C
Fig.4: the Hall
Effect circuit
board, once it’s unsnapped from its
plastic housing and with leads soldered on.
Fig.3: each phase is fourteen coil windings in series terminated together
at a star point. Normally these drawings portray the windings in a star
formation (like Fig.7).
connected in series (see Fig.3) and terminated in a star point.
Motors are made up this way to decrease their speed and
increase their torque. With 56 magnets and 42 coils, each
step is tiny and a sequence of six steps will only take the
rotor around by a fraction of a turn (look closely at Fig.1).
But the torque will be high as each energised coil winding
will be attracting a magnet that is only a small distance away.
Don’t think that the SmartDrive is slow though; the story
goes that during development the motor was tested for
maximum speed and resulted in a load of laundry being
turned into confetti!
Disassembly
Removing the stainless shaft is accomplished by undoing all of the nuts you can see and pushing the shaft out.
It only takes a gentle tap with a soft mallet to get it moving
and if you find that it won’t go, keep looking for more nuts
around the shaft.
There is a little carrier for the Hall sensors. I found it was
easy to take off once the rotor was removed and it simply
slides out to reveal the circuit board as shown in Fig.4.
Stepping Motor
Once you have the motor mounted so that it will rotate,
it’s time to take it for a basic test run.
Fig.1 shows the input terminals arbitrarily marked as A,
B & C and I also went around and labelled all of the coils
in the same way.
I used a series of three 12V batteries to give 36V and
applied power to the input terminals in the order shown
in Table 1, where A+, B- means to connect A to positive
and B to negative.
If you follow the sequence, you will find that the motor
steps smartly around and you may also find that you get
a bit of a zap from the terminals. That’s called inductive
kick back and now you know what that term means in a
way that you’ll find hard to forget!
Standing back and considering what you’ve just done,
you’ll realise that you have effectively driven the SmartDrive as a stepping motor; a very useful device in its own
right.
Clearly, nobody wants to stand around swapping leads
all day but everything else is in place, so the only barrier
between you and a high-powered stepping motor is to find
some way to drive the motor electronically.
A schematic version of what is desired is shown in Fig.5.
Simply closing switches A(high), B(low) will cause the
motor to take the first step on Table 1 and then opening
B(low) and closing C(low) will take the next step and so on.
Reversing the order of switching will make the motor
run in reverse.
Building up the schematic using real switches will give
you quite a handy little motor tester but most people will
want to replace the switches with Mosfets and drive them
with a suitable microcontroller, perhaps an Arduino or
Picaxe.
+V
AHIGH
+V
TAB IS ALSO GROUND
ALOW
RP
6.8k
A
B HIGH
HALL
SENSOR
C HIGH
ADDED
PULLUP
RESISTOR
C
220
B
R1
B LOW
Fig.5: six switches wired to test
the motor. The same arrangement
using transistors is used to run the
SmartDrive as a stepping motor or
as a full BLDC motor.
siliconchip.com.au
C LOW
C4
OUT
OUT TO
CONTROLLER
C1
GND
Fig.6: circuit diagram of the Hall Effect sensors.
Resistor RP is added to pull up the Hall chip’s
open-collector output.
February 2012 17
A
A1
A2
A3
2 x COIL
WINDINGS
IN SERIES
A4
C2
B2
C4
C1
B1
B4
B3
B
C
SEVEN OF THESE
GROUPS IN PARALLEL
Fig.7: this is a series-parallel connection. The coil windings
are cut and joined to give a group of two coils in series and
then wired together to form seven groups in parallel.
I never had the need so I didn’t do it – I’ve pulled apart
enough copiers and printers to have a good supply of
powerful stepping motors (big copiers now have BLDC
motors too!).
It shouldn’t be too hard to find a suitable H bridge stepping motor driver, though (eg, SILICON CHIP, April 2011
Circuit Notebook).
In fact, there is nothing to stop you hacking the original
washing machine controller and driving the Mosfets with
your own micro.
A warning about voltages: you must not try to use the
SmartDrive as a stepping motor at the original voltage! The
motor is made to run at some 200VDC and it needs this
voltage to run the motor at high speed.
Stopping the motor with high voltage still applied will
result in much smoke. For stepping applications, even
fairly fast stepping, you will find that 48VDC is more than
adequate.
Having said that, stepping motors can also be used as
brakes and I recommend starting with perhaps 12-24V
to give a good compromise between strong braking and
overheating the motor.
Closing the loop
To run the SmartDrive as a fully fledged BLDC motor, the
next part to be addressed is the hall sensor board.
Referring again to Fig.4, you will see that the sensors
require a voltage supply (red and black wires) and output
their signals on the blue, green and yellow wires. I found
that the sensors are open collector, meaning that they are
effectively open circuit until a magnetic south pole is
brought up to the face of the IC.
To run an open collector circuit, a pull up resistor is
needed and the complete circuit is shown in Fig.6, with
components C1, C4 & R1 being originally present on the
board.
It would be easy enough to solder the pullup resistor onto
the original board but I ended up making a super simple
extension board with a scrap of Veroboard so I could get
my multimeter onto it more easily.
Building shouldn’t take more than a half hour or so and
then you’re ready to test.
Simply apply any reasonable voltage to the power leads,
say 12V, and measure the voltage at each output while applying a small magnet to the Hall sensors. By alternating the
magnetic poles, you should see the output voltage swing
18 Silicon Chip
between approximately 12V and 0V.
For interest, you might like to reassemble the motor and
run through the manual test sequence while noting the hall
voltages. If all is well, you should get the results of Table
1 with ‘0’ being 0V and ‘1’ being 12V.
Motor driver
The last step is to select a suitable motor driver. I originally thought of using the driver that was build into the
washing machine but in the end decided that it was more
trouble than it was worth.
For a start, the washing machine driver runs on full mains
voltage and I wanted a system that would run on 36 or 48V.
It is possible to rebuild all of the various power supplies
but there is a fair bit of work involved.
The final nail in the coffin was the fact that the central
processor appears to run the whole show, including all of
the motor functions. The processor would run my motor
but I would have to put up with any machine powered
by the motor going through periodic wash, rinse and spin
dry cycles!
In the end finding a suitable driver turned out to be a
fairly simple task. Realising that the SmartDrive is a fairly
typical and increasingly common BLDC motor, it was a
matter of finding a class of machinery that used such a
motor and discovering what they used as a driver.
The answer turned out to be electric vehicles, especially
electric mobility devices. The driver I bought will handle
36V and 50A for a total of maybe 1500W output, once a bit
is subtracted for losses. There is a slightly more powerful
version available that runs 50A at 48V but that was rather
more than I needed.
As is increasingly common, the driver is Chinese made
and I found the original version on www.made-in-china.
com
A hunt around using the world’s favourite search tool
will turn up legions more; the only fly in the ointment
being that most suppliers are located in China and the
Chinese are not big on credit cards and like to ship orders
via containers on ships.
I bought a few units and can offer them to readers for $149
plus a few dollars for shipping – see the list of sources at
Fig.8a: complete system, ready to run. I built the bearing
housing to suit a particular application but most people simply
chop out the entire Nylon bearing housing from the bottom of
the washing machine drum and strap it down with U bolts.
siliconchip.com.au
the end of this article. I’m also in the process of ordering
a 60V and 240V version and if you’re interested, drop me
a line at contact<at>energy1000.com.au
For the intrepid soul, there is quite a good selection of
drivers available on eBay.
The sellers are generally folks who sell a wide variety of
goods and so have no product knowledge or factory info
available but with the procedures outlined in this article,
it should be relatively straightforward to sort out any combination of controller and motor that you might encounter.
Just don’t try to drive a SmartDrive motor with a driver
intended for a 200W bicycle!
Putting it all together
One of the biggest problems I see being wrestled with on
the discussion groups is the matching of a (generic) driver
with a (different generic) motor.
Even the best manufacturers are notoriously short on
information and there is most certainly no universal colour
coding system for the drive and sensors.
The general approach is ‘trial and smoke’, with hot lists
of ‘Motor X works with Driver Y’ being gleefully circulated
once a working combination is found.
The driver I used (see Fig.8b) dispenses with all that
unpleasantness by offering a self calibration function. Even
more amazingly, it works!
By simply activating self calibration and first pulling
the motor backwards and then forwards, the micro gets
enough information to sort out the coil to Hall Effect sensor phasing and with a twist of the throttle, away it goes.
Gotta love this modern technology!
Self calibration also makes wiring very easy. The driver
comes with pre-wired plugs that are nicely labelled and the
only thing to be careful of is to wire the Hall Effect power
supply from the driver to the correct leads on the Hall Effect board (have another look at Figs. 4 and 6).
I then wired the rest of the Hall Effect leads as shown
in Fig.4 to the same colour leads on the driver and then
randomly assigned the fat yellow, blue and green power
leads to motor phases A, B & C in that order (have a close
look at Fig.1). The fat black and red leads are then obviously the 36V power supply.
Fig.8b: generic Chinese driver with the leads separated into
their functional groups. In front are the Hall Effect sensor
leads with the same colour coding as Fig.4. The throttle pot
is at front and the fat yellow blue and green leads at top right
are power to the motor.
siliconchip.com.au
Components and further information
Bearing housings, various parts, windmill blades and all
sorts of good information can be found at
www.thebackshed.com/windmill and also
www.ecoinnovation.co.nz/
Motor drivers of all sorts can be obtained from Millenium
Energy Pty Ltd. The driver used in this article is available
for $149 at time of writing.
Email: contact<at>energy1000.com.au
Chinese manufacturers web site having every type
of product imaginable: www.made-in-china.com
I used a 5k pot as the throttle but nice twist-grip throttles are readily available from eBay or some SILICON CHIP
advertisers.
The driver supplies 5V and ground to the pot and the
0-5V control signal then comes off the pot wiper. Again,
all quite simple – and most manufacturers will supply at
least a rudimentary wiring diagram.
You will find that the motor will only run fairly slowly,
which is to be expected as the coil windings are originally
intended for mains voltage and a puny 36V has trouble
convincing them to magnetise at any great rate.
Series, parallel or both?
The solution is to realise that the coils are all connected
in series and for lower voltage applications it is entirely
possible to connect groups of them in parallel.
The process to do it was covered by Glenn Littleford
in SILICON CHIP in a series of articles starting in December
2004 (siliconchip.com.au) and can also be found at www.
thebackshed.com/windmill/Contents.asp
The final arrangement is as shown in Fig.7, commonly
referred to as a ‘series – parallel’ arrangement because a
number of coils are connected in series to form a group and
the groups in turn are connected in parallel.
Note that it is also possible to connect the coils together
in simple parallel which will allow the highest possible
current at the lowest possible voltage, exactly opposite to
the original windings.
The choice of exactly how many coils to connect in parallel groups is largely determined by the application and
by experience in operation – in fact you may notice that
Fisher and Paykel themselves have made many modifications to their motor since it first came out.
For my application, the motor produced good power
and speed and hummed along under load without any
overheating.
The best advice I can offer is to get a hold of a good book
on magnetism and motors (SILICON CHIP sells a couple of
good ones) and put in some motor operating hours.
The complete system is shown on the test bench in Fig.8a,
with the driver box connected to the coil windings and
the Hall Effect sensors. At left, near the spline, is a roller
bearing in a pressed metal housing which unfortunately
didn’t sit flush on its mounting flange and so needed three
little bobbins as standoffs.
By the time you’re reading this, I will hopefully have
machined off the spline and mounted a small pulley to
SC
drive a ‘V’ or cog belt.
February 2012 19
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