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Salvage It!
By BRUCE PIERSON
What can you do
with a dead
UPS... or two?
If you’ve been following
our recent series on ratting
various equipment for parts,
you’ll realise that there is a lot
more to it than meets the eye.
Mostly you’re just recycling
components for the junk box...
just in case! However, when it
comes to Uninterruptible Power
Supplies, they could be the start
of a very worthwhile project.
Especially if you happen to lay
your hands on two of them!
U
ninterruptible Power Supplies (more usually abbreviated to UPSs) are actually a misnomer. They
certainly ARE interruptible – they are designed
to give you enough time to save your work and then shut
down the computer properly if there is a blackout (or even
a momentary power interruption).
They do this by instantly switching over to a batterypowered inverter when there is any loss of mains power.
However, with rare (read $$$$!) exceptions, they are
not designed to let you keep working indefinitely. That’s
because the internal battery will only deliver power for a
relatively short time. And when that battery runs down,
you’re definitely powerless! Or up the creek without a
paddle. And so on!
The reason most UPSs fail is that their batteries fail – and
that’s usually a relatively easy fix. Replace the battery (in
most cases, they use SLAs) and the UPS should be good
for another couple of years or so.
Because SLA battery failure is so common – and to help
82 Silicon Chip
prevent it, SILICON CHIP published the “Battery Lifesaver”
in the Septermber 2013 issue. If you use SLA or Lithium
batteries, it’s well worth a look – you could save a lot of
money in batteries!
But there are other causes of failure, too – and like
many things electronic, replacing an old, tired UPS with
a modern one usually makes more economic sense than
troubleshooting and fixing it.
Ergo, you might come across a “junked” UPS one day.
But before attacking it for parts, if you have a suitable (ie,
same voltage, even if not the same capacity) SLA battery that
you can easily hook up, you might find it’s a goer. Lucky
you: replace the battery with one of the same ratings and
you won’t have to worry about losing work again!
Strip it!
But if it doesn’t kick into life, don’t bin it: you could
strip it for parts. Assuming that the transformer itself isn’t
the part that failed, at the very least you will have a quite
siliconchip.com.au
First step in diassembly is to get the covers off – and some manufacturers treat this as an intelligence test! Hidden screws,
specific order of removal and so on can often be a real pain. But in the case of UPSs, they know that at some stage the SLA
batteries will have to be replaced so they usually aren’t as difficult as many other devices. Incidentally, before we started
disconnecting everything we temporarily replaced the batteries to make sure these units were dead. They were!
“grunty” low voltage transformer, (usually about 12-20V at
perhaps 10A) along with attendant rectifiers and so on. Of
course, those bits are very handy in their own right – for
instance, you can make quite a nice battery charger – or
you can make up a great low voltage bench power supply.
If you’re fortunate enough to come across two (identical)
UPSs, you might think about making an isolation transformer (more on this one anon).
But let’s first look at breaking down a UPS for parts.
The pictures above show two UPS units. The smaller,
black one has a plastic case, whereas the larger white one
has a steel case with a plastic front panel. The smaller one
is a newer model which was fitted with a single 12V SLA
battery while the larger, older one was fitted with two 12V
SLA batteries.
Where to start? It goes without saying (so we’ll say it
anyway!) – unplug the UPS from the power before you
do anything.
We’ll start with the smaller unit with the plastic case.
These cases are a bit of a hassle to take apart. First remove
the front panel. This is usually held on by a clip or clips
at the bottom of the case, so it’s a matter of working out
how the clip works, so that it can be disengaged and the
front panel removed. After that, there will be a number of
screws securing the two sides together, so once these are
removed, the topmost panel can be lifted off to reveal the
contents of the UPS.
For the larger unit with the steel case it is more straightforward to remove the cover. It will usually simply have
screws holding the cover on and once these screws are
removed, the cover can be slid backwards and/or tilted up
from the back to remove it.
Now that the cover is off, it’s just a matter of proceeding
to undo screws and remove all the parts and we can see
what we have from the exercise. The parts available will
vary from one UPS to another, depending on their age and
rating. Other UPSs may have somewhat different parts to
these units, but something similar.
So, what did we get from these two UPSs? We’ll start
with the smaller unit. The picture below left shows the
partly disassembled UPS.
From this unit, we salvaged the following parts:
• A plastic case that could be good for a project. However, it will
be necessary to make a new rear panel for it, due to the sizes of
the holes in the existing rear panel. This is straightforward, as it
just requires a suitable piece of hard plastic or aluminium. The
old panel can be used as a template, once the parts are removed.
• A transformer with output voltages of 7V – 0 – 7V at 10A or more
plus 15V at 1A
• Two mains sockets (often UPSs will have IEC sockets, which are
The two UPSs partially broken down. The one at left is
significantly simpler (and lower capacity) than the older
model at right – the advantage of the older model is that
yielded significantly more bits and pieces.
siliconchip.com.au
May 2014 83
Another very worthwhile
commonly used in projects)
exercise in salvaging very use• One IEC male mains socket
ful components from what was
with built-in fuse. Handy for
a “useless piece of junk”.
use in a project instead of a
The larger steel case will be
standard mains cable.
This is a mains-operated device and very useful for a project and
• The dead battery went to the
recyclers (never put dead
all wiring must be run using 250VAC the power transformer is parversatile, with a large
batteries in the garbage bin).
rated cable. Any exposed metal (eg, ticularly
range of output voltage options.
• A PCB with the following
screws) must be earthed. If you use There are even four big power
components for later removal:
the metal cased version of the UPS, transistors already on a large
• nine electrolytic capacitors,
heatsink that can be pressed
five 3A diodes, two 1A diodes,
ensure that the case is earthed.
into service.
four relays, one IC, one 5V
Not all UPSs will have such large heatsinks and power
regulator, two TO-220 transistors, three dual diodes, one small
heatsink, two high voltage capacitors, one USB B PCB socket, transistors, as newer models tend to have smaller compoone small PCB speaker and a range of SMD components on the nents than the ones in this particular UPS.
Any salvaged components must, of course, be tested to
back of the PCB.
So that was a very worthwhile exercise. The power trans- make sure they are good. Never use an untested component
former in particular will be very handy. It’s just a matter of in a project or a repair, because if the component is faulty,
adding the other components and you’ve turned a useless you will be introducing a fault that wasn’t there to start with.
piece of junk into something useful.
Now we’ll look at what we got from the larger, steel Testing the transformer
When you have a transformer with unknown conneccase unit:
• One steel case with a plastic front panel. This case is not in the best tions, especially from equipment that wasn’t working, it
condition but it can be resprayed easily. We left the mains switch is necessary to determine which wires are which. Most
and the two fuse holders in it. The other holes can have a small important is the primary – the mains input. If you wire
plate fitted to cover them. The mains cable was removed and an it up incorrectly, you can permanently damage the transIEC socket will be fitted, instead of having a captive mains cable. former and blow a fuse or trip a circuit breaker. Often, a
• One transformer with outputs of 16V – 0 – 16V at up to 10A UPS transformer will have multiple wires that could be the
plus 28V at 1A – 2A and 15V at 1A and 35V at 1A. A very useful mains input, or could be a low voltage output at a lower
amperage, so it’s important to differentiate between them.
transformer suitable for many projects.
Before you start, make sure you are using a power point
• Two PCBs with the following parts for later removal:
• 16 electrolytic capacitors, 17 ceramic capacitors, seven greencap that is protected by a safety switch (also known as an RCD,
capacitors, five tantalum capacitors, four TO-3 power transistors, or residual current device). If you are in a building that
one LM317 voltage regulator, three TO-220 transistors, four 5W does not have safety switches either at the switchboard
resistors, eight ICs, four trimpots, 14 small transistors, four PCB or as part of the wiring, then buy a portable safety switch.
These are not expensive and could save your life if you
fuses, one relay, two X2 capacitors, one thermistor, one mains filter
choke, one 30W resistor, one large heatsink, one small heatsink, happen to contact a live wire.
Incidentally, if you are not sure if there is a safety switch
a range of SMD components on the top of the PCB, two mains
sockets, five brass threaded PCB stand-offs, three cable tie-points, or not, there’s no harm in connecting a portable safety
two cable ties, one mains cable, one mains cable clamp, some switch to a circuit which already has one.
So here’s the best way to proceed. First, identify any very
hookup wire, eight screws, three nuts, two spring washers, two
thick wires. These will be secondaries. If you only have one
insulation sheets from under PCBs.
set of thick wires and one set of thinner wires, then that’s
pretty straightforward, as the thinner wires will be the primary. However, there may be multiple sets of thin wires, so
some caution is required. First, test these wires with your
multimeter and find out just how many sets of wires are
connected to individual windings. Having identified the
individual sets, choose the set with the highest resistances.
A typical transThen in this set, identify the two wires with the highest
former (not from the
resistance between them. These will more than likely be
UPSs) showing the
various windings
the ones to connect to the mains and in many cases will
– the primary, in
have the same colour insulation or may even be coloured
this case, is the redbrown and blue (or red and black in older transformers).
sleeved pair, with
Next, use a mains-rated terminal block to connect the
three secondaries
Active and Neutral wires from a 3-wire mains cable to these
– white, blue and
two wires, with the earth wire to the frame of the transyellow (with black
former. Again, for safety this should be done on a circuit
centre-tap).
fitted with a safety switch at the switchboard (ie, an earth
Use a multimeter on
leakage detector or RCD) or if there isn’t one, use a mains
a low Ohms range to
lead fitted with a portable unit.
identify the
different windings.
Plug the cable in and turn on the power. Assuming it’s
WARNING!
84 Silicon Chip
siliconchip.com.au
A
230V
AC IN
N
TRANSFORMER 1
1:1
TRANSFORMER 2
A
ISOLATED
230V
AC OUT
230V
AC IN
N
~12V
AC
~12V
AC
ISOLATED
230V
AC OUT
Fig.1: a “traditional” isolation transformer has two
identical windings – feed a voltage in one winding (the
“primary”) and you’ll get a very similar voltage on
the other (the “secondary”). However, the two are not
connected in any way. While this has theoretically identical
voltages, you can expect minor losses. And you do need to
ensure the power rating of the transformer is not exceeded.
Fig.2: you can make an isolation transformer using two
indentical transformers connected “back to back” – this
achieves exactly the same result as a single transformer with
two windings. Once again, the power rating is important –
you cannot draw more current from the transformer than
it was originally intended to supply. Losses will be slightly
higher because two transformers are used.
not humming or buzzing madly, getting hot or smoking,
you can now carefully measure what voltage is on each of
the secondaries and make a note this, either by writing on
the transformer or by putting tags on the wires. Use your
multimeter on a suitable “AC volts” range.
You may think that you can’t use a UPS transformer as a
mains transformer, because the operation of the UPS is to
turn battery power into mains power. However, this is only
when the power goes off. In standby mode, the transformer
actually supplies low voltage to keep the battery topped
up and to power the rest of the circuit. When the power
goes off, a relay trips and changes the mode of operation
to supply mains equivalent power from the battery, so it’s
perfectly safe to use a UPS transformer permanently as a
step-down transformer. Just don’t try to exceed the current capacity of the transformer. This rule applies to any
transformer, regardless of its type.
ing the Active is often enough to kill you due to the path
through your body and feet to earth – which can be a damp
floor, metal frame of a building, and so on. The point is,
electricity flows through your body and upsets the impulses
controlling the muscles which make your heart beat.
With an isolation transformer, because its output is not
referenced to earth, you can accidentally touch either wire
with relative safety, even if you’re standing in a puddle
of water! But touch both at once, if you form a path via
your heart (eg, from hand to hand) you can get killed just
as easily!
A couple of “for instances”: if you are working on mainspowered equipment with a “live chassis”, then an Isolation
Transformer is a must for safety.
Another situation would be trouble-shooting an earthed
appliance that has a slight earth leakage. If you don’t have
a safety switch, this appliance will happily function normally without any problems. However, if you have a safety
switch, then you can expect the safety switch to be tripped
either repeatedly or on a semi-regular basis. That’s a good
indication that you have a fault, by the way – something
that must be corrected as a matter of urgency. An isolation
transformer will help locate the fault without continual
tripping of the safety switch.
Thirdly, an isolation transformer may be of assistance in
tracking down various other mains-related faults.
Why not make an isolation transformer?
If you’re lucky enough to come across two identical
UPSs, you’re going to end up with two identical power
transformers. How about connecting them together to
create an isolation transformer for general service work,
troubleshooting and so on?
What is an Isolation Transformer? As its name suggests,
it’s a transformer that supplies a voltage isolated from
another – in this case, 230VAC which is not connected
to, or referenced to, either the mains or to earth. In simple
terms, you feed in 230VAC from the mains and you get out
230VAC that isn’t connected to the mains.
Why would you want to do this?
As you would know, the 230VAC mains normally has
three wires, the Active, Neutral and Earth. Two of these, the
Neutral and Earth, are (or should be) connected together
at your switchboard so theoretically at least, are at earth
potential, or 0V (this assumes you have a good Earth connection, which isn’t always the case).
The Active wire has a potential 230VAC relative to
Earth. Having Neutral and Earth at 0V has both good and
bad points. It’s mainly a safety measure where a fault to
earth will generally be enough to blow a fuse, rendering
the device relatively safe.
However, the bad point is that if you touch the Active,
the chances are very good that some part of your body will
be at Earth potential and you will receive an electric shock
which is at best life threatening.
Note that you don’t have to physically touch both the
Active and Neutral/Earth lines at the same time. Just touchsiliconchip.com.au
How is an isolation transformer constructed?
In the vast majority of transformers, (of any description)
the primary and secondary windings are isolated from
each other – in fact, the isolation is often specified and it
should be rated at several thousand volts. Primaries and
secondaries are usually wound on two halves of a plastic
bobbin, thus both physically and electrically isolated. Even
transformers where the primary and secondaries are wound
over each other – such as a toroidal transformer – have very
good insulation between the two.
So it is with an isolation transformer, except that the
primary and secondary windings are identical.
Feed 230VAC (from the mains) into one winding and
you’ll get (by transformer action) an isolated 230VAC from
the other winding (ignoring losses).
Incidentally, auto-transformers are the exception: here
the secondary is connected to the primary. So they can be
dangerous beasts to be treated with due diligence!
How are we going to replicate this arrangement?
Remember that with any transformer, the voltage out is
May 2014 85
Fig.3: here’s the final cicuit of our isolation transformer – very similar to Fig.2 but with the addition
of a fuseholder (part of the IEC mains input
connector), a power switch, an earth connection
to both transformer cores plus a neon indicator
to show that power is available. While the circuit
shows “~” 12VAC secondaries, any roughly similar
voltage will be fine, as long as both are identical.
A
FUSE
230V AC
IN
(FROM MAINS)
N
E
simply a function of the voltage in and the “turns ratio”.If
you have a transformer which is normally 230VAC in and
12VAC out but feed 12V AC into the secondary, you will
get 230V out from the primary.
Which is exactly what we are doing here: we will use
two identical UPS transformers and connect the low voltage windings together to achieve this result. Fig.1 shows a
conventional Isolation Transformer while Fig.2 shows our
version of an Isolation Transformer.
As long as we keep within the power rating of the transformers, we get what we want – isolation between input
and output.
Making it
First, we need two identical transformers from old UPSs.
These must be identical in order for the above arrangement
to work correctly and produce the same voltage at the output
as the input. Next, we need a power switch, a fuse, a neon
indicator with, say, a 150k resistor and a case.
Usually, one of the UPS boxes that gave you one of the
transformers can be pressed into service. It will already have
the mounting positions for one transformer, so it should
be relatively easy to mount the second transformer. The
components are wired up as in Fig.3.
Assembling the unit
Now that you have a suitable case and you have been able
3A
TRANSFORMER 1
ON
POWER
~12V
AC
TRANSFORMER 2
~12V
AC
NEON
100 –
150K
ISOLATED
230V AC
OUT
DO NOT EARTH
TRANSFORMER 2 OUTPUT
to mount both transformers in the case, it’s time to wire it all
up. Follow the circuit diagram above and the photo below
to make sure that everything works as expected.
We used two transformers with centre-tapped 15.5VAC
secondaries. The centre-tap was not used, so these wires
were coiled up out of the way – make sure that any bared
ends of wire are suitably insulated.
Due to the thickness of the wires on the secondaries, it
was decided that the most practical way to connect them
together was to use a heavy-duty terminal block as shown
in the photo below.
The primary wires on the input transformer were soldered
to the terminals on the power switch and IEC socket while
the wires on the output transformer were joined to the wires
from the GPO socket on the back panel and soldered and
heat-shrinked.
This particular case had two GPO sockets on the back
of the case. We removed one, to comply with Australian
Standard AS/NZS61558, which only allows one outlet on
an isolation transformer. It also had a fused IEC socket as
well as two other holes. One hole was filed out to suit the
power switch and the other hole had a piece of black plastic
super-glued on the inside to fill it in.
The picture below shows the arrangement with the UPS
case and transformers that we used.
The original case required some minor modifications to
house the second transformer which was housed where the
The transformers in the UPS had 15.5VAC CT secondaries – we cut off the centre-tap and used the full 15.5V windings.
While this photo shows wiring “salvaged” from the original UPS, wiring should be made using 250VAC rated cable and
to modern wiring practices. In particular, no 230VAC wiring should be run using ribbon cable. We’d also like to see a
few cable ties used to make wiring captive. If using a metal case, it must be earthed. Isolation transformers are for safety:
keep it that way! But regardless of the type of case, the output socket Earth pin must remain disconnected.
86 Silicon Chip
siliconchip.com.au
battery was originally located. As the transformer was thicker than the battery, the case had some of the ribs trimmed
back by initially clipping them out with side-cutters and
then finally trimming them level with a wood chisel.
Be sure to wear safety glasses while performing this
operation, or you might find yourself wearing a sliver of
plastic in your eye instead. Very unpleasant!
If using a steel case, it will most likely be easier to mount
the second transformer on the base of the case, adjacent to
the original transformer.
The case we used originally had three LEDs on the front
panel. We removed the three LEDs and replaced the bottom LED with a neon indicator and fitted an appropriate
resistor, in this case 150k1W (1W needed for its higher
voltage rating), as this miniature neon did not have an
integrated resistor.
The photo at right shows the front and rear of our Isolation Transformer. It now has one power outlet, a fused
IEC connector and power switch. It might appear that the
fuseholder/fuse is on the “wrong side” of the power switch
– surely it should be after the switch so that the mains is
not connected when the switch is off?
In theory, that is absolutely correct; however, the fuseholder is integrated within the IEC mains input connector
so must be connected this way around. The fuseholder cannot be accessed unless the IEC mains plug is first removed.
The remaining hole on the left-hand side of the back panel
near the bottom was filled in by gluing a piece of black
plastic to the inside of the back panel with super-glue but
epoxy glue would be a better choice.
So there you have it. An Isolation Transformer for very
little cost. Just wreck two identical dead UPSs and use the
Front and rear of our UPS-based Isolation Transformer.
We’ve mounted the second transformer inside the case and
removed one of the outlets on the rear panel. The bright red
Neon shows that the unit is powered up.
two transformers and a few other bits and pieces and one
of the cases.
We now have a useful workshop device – at a saving of
around $400 over commercial devices.
Not bad for an afternoon’s work in assembling the unit,
as we had the required parts on hand from previous recycling exercises.
SC
In one word:
Magnificent!
Is this the world's most efcient true hi loudspeaker?
With an efciency of 97dB/watt, it could be!
Is this the world's loudest true hi loudspeaker?
It easily could be. With power handling of 300 watts it
can produce sound levels in excess of 120dB!
Is this the world's “bassiest” true hi loudspeaker?
It probably is, with a bass response all the way to
below 20Hz. No, that's not a misprint!
What else? How about typical harmonic distortion of
around 0.3%. That's really low!
OR how about a piano-nish cabinet in a large range of
surfaces – that anyone can produce.
Or how about the fact that it uses a massive 15-inch
loudspeaker made in Australia?
Or that even with its exceptional bass response, it has
a treble that really sings?
Have we whet your appetite? Good. Because you’ll nd
the construction details in the June issue of SILICON CHIP.
On-sale date: Thusday, 29th May.
siliconchip.com.au
May 2014 87
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