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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 150k1W (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