Guide: plugpack selection

This question has always been a popular one, but seems to be more and more frequent these days. So, here is a one size fits all answer to replacing a plugpack. Please post comments in the thread and I'll update as needed. Questions about specific situations/devices which are already addressed in this post will be ignored - please read carefully before asking. Please don't PM me asking for individual assistance - if I haven't already answered your question here you'll get a better result by asking in the forum.

DISCLAIMER: the below is given for information purposes only, and is not to be considered as advice. You must make your own decisions about what is appropriate for your circumstances, and seek the counsel of qualified persons if you are not qualified to do so. Any of the actions described below could result in damage or injury to your person or property. Neither the poster, nor Overclockers Australia, accepts any liability for any injury, costs or damages arising from the use or misuse of this information. All care is taken to ensure accuracy and completeness, but no responsibility is taken for any errors or omissions. Proceed at your own risk

You've got an item from overseas, or a second hand item missing parts, an in-car device that only has a car charger that you want to charge at home, a device which only has a mains charger that you want to run in your car, or a device whose plugpack has failed, and you need a way to charge or power it. Depending on the device and the circumstances, this can be solved in one of a few ways.

Determining what your device needs
First, look at what you've got. Marked on the device should be a description of its power requirements. The device might say something like "6VDC 500mA" or "19V_ _ _ 3.5A" (the _ _ _ means the same as DC). It might say 12V 18W, which means you need 12V 1.5A (divide the power rating, given in Watts or W by the voltage, V, to get the current, given in amps or milliamps, A or mA. 1000mA=1A). It might say something like "6-12VAC, 1A", which means you need an AC plugpack, but it can be any voltage between 6 and 12. A DC device might give a range too. Write these numbers down. Don't panic just yet if there are no such markings anywhere on the device, you might get the info from the supplied plugpack or car charger.

Checking if you already have what you need
Next, if it was supplied with a plugpack or car charger, take a look at it. It should have similar markings. It should also have an input power rating. It might say something like:
Input: 100-240V~, 50-60Hz, 1.7A
Output: 19V_ _ _ 3.42A
This means that it can be connected to a wall outlet delivering any AC voltage (the "~" symbol means AC) within the stated range of 100-240V. Here in Australia, our power outlets deliver 240VAC 50Hz. A standard domestic/office outlet can deliver anything up to 10A.
Check the output numbers and compare them to what you read on the device. The voltage should be the same, or within about 10%. If it's a completely different number, you might have been given the wrong plugpack - use the numbers written on the device to continue selecting a replacement pack. Don't worry if the number for current (A,mA) on the plugpack is higher than on the device - this is entirely normal, and a supply with a higher current rating will work on a device with a lower current requirement. It doesn't work the other way around though - the plugpack must have the same or higher current rating than the device needs.
If your original plugpack's input says 100-240VAC, you don't need to buy a replacement plugpack. You can purchase a plug converter from Jaycar, Dick smith, Tandy or other electrical/electronic retailer which changes the pin connection from whatever country our device came from to the Australian standard, but doesn't change the power coming out of your socket. This is usually cheaper than any of the other options, should be less than 10ドル. If it's a laptop, or other device with an "inline" type supply, which has a detachable cable that runs from the wall to the plugpack, you don't even need to use an adapter. From the electronics suppliers you can buy a replacement lead which has an Australian wall plug on one end, and an IEC (kettle/computer PSU style), cloverleaf (shaped like a cloverleaf) or C8 (shaped like a figure 8) connector at the other end. If the device came from Europe and says input 220VAC, this is usually fine too, as most things have a fair degree of tolerance for small differences in power supply input. If this is you, you're off to buy a converter and can stop reading here.
If it says 100-120VAC or similar low voltage, you will need to replace the plugpack, or purchase a stepdown converter. Replacing the plugpack is the cheaper, and preferred, option in most cases.

Choosing a replacement
Having inspected your device and/or the supplied plugpack, you should now know what voltage (V) and current (A, mA) your device needs. If not, go back to the top of this post, read it again, and check your equipment again. You can now select a suitable replacement. Jaycar's catalogue of plugpacks can be found here,here,& here, with an easier to browse reference list at the bottom of here, Dick Smith's can be found here. Select the plugpack which most closely matches your power requirements. If the voltage is within about 10%, this should be okay (eg a 5V supply will usually work for a 4.7V device). The current must be the same as or higher than the device's requirements - you can use a 2A supply for a device which needs 1A, but you can't use a 500mA supply. The ones which have multiple voltages are fine, and you can use them to power several different devices with different voltage requirements, but they are more expensive than fixed voltage units, and they have the potential to damage your device if you accidentally hook it up with the wrong voltage selected.

I appreciate that the websites have many supplies to choose from, and most of them are not what you need. You'll get better results by going into a store and looking at the plugpack display, or asking a sales assistant to help you find one. Don't let them give you one which is too low in current, the wrong type (DC versus AC) or much larger than your requirements (eg a 10A supply for a 1A device). Not all salespeople have excellent product knowledge, so they may give you one which won't work, or is overkill for your needs. In most cases though, it should be relatively easy - a switchmode type 5, 9 or 12V supply with 1-2A capacity. Most of the available plugpacks will have a set of interchangeable tips. Make sure before buying that one of these tips fits into your device's socket.

Connecting to your device
As stated, most plugpacks have interchangeable tips. They also have changeable polarity. See how the tip can fit either way onto the end of the cable? You need to make sure the polarity is correct before connecting to your device. You do this by looking at the device or the supplied plugpack for a symbol that looks like this:
(+)---(o---(-)
or this
(-)---(o---(+)
The first one means centre negative, or tip negative. The second one means centre/tip positive - see how the + symbol is connected to the inside circle? Most devices, if they don't have such a symbol, are centre positive. It means that, looking at one of those barrel connectors, the inside contact is positive and the outside is negative, or vice versa. The PSU you get should have instructions for how to hook this up. The Jaycar one is marked "tip" on the cable, and + and - on either side of the barrels. If your device needs centre positive, just line up the "tip" and + symbols, connect them together, plug it into your device and enjoy. Obviously vice versa if you need centre negative.
This is only necessary if your device takes a DC supply. AC supplies have no polarity, and the tip can be connected either way around with no problems.

If your device doesn't have such a symbol, but you've got a supplied overseas plugpack, have a look at it - the marking is often on the body of the plugpack. If it's not marked on anything, you can either search for more information (talk to the manufacturer etc), or take a punt. If you're taking a punt, almost everything these days is tip positive, with the exception of some audio equipment (9VDC tip negative supplies are fairly common in that industry). If you connect it backwards, the possible outcomes are that it works fine either way (if it has internal rectification); that it doesn't work, but does no harm (if it has internal protection diodes); or that it fails and damages the device in an amusing or dangerous fashion (fairly likely if it's dodgy enough not to have the polarity marking). Good Luck!

Special cases
Laptops
Laptops need much larger supplies than most small electronic devices. The electronics suppliers sell adjustable voltage supplies specifically designed for laptops. They also sell such supplies for in car use, which means you don't need to use an inverter to charge your laptop in the car (this is relevant even if you've got the mains charger). Inverters for laptops are tricky beasts anyway, as they need to be a particular type of inverter (pure sine wave) with much higher power rating than your laptop appears to require. Avoid the whole expensive exercise by getting a cigarette lighter to laptop supply with a suitable current rating and use it in place of your normal mains charger. Check the tip connector first though - laptop manufacturers are notorious for using supplies that have non-standard connectors. If this affects you your only option may be to cut the end off your supply and solder the leads to the new supply, or use it to make up an adaptor.

Audio Equipment
Audio equipment is often slightly different to other devices. In particular, the small, light, cheap switchmode supplies that can be purchased aren't favoured, because they can introduce noise into the device. Look for a regulated transformer type of supply - these are available from the electronics suppliers alongside the switchmodes, and are characterised by generally being bulkier for the same current rating than switchmodes. You may also choose to use a transformer supply which is marked as "unregulated" but be careful to choose one which has close to the right current rating - unregulated supplies with much higher current capacities than the device needs will put out a higher voltage, which could in some cases harm the equipment. 0-50% higher than needed should be okay though.
The other peculiarity about audio equipment is that they seem to be the only devices around these days which still use negative tip supplies. Check the polarity carefully before connecting.

Cordless drills, and other devices which need a charger instead of a power supply
Most devices have their charging circuitry built into them, and the plugpack just delivers power to it, but some things, including many brands of cordless drills and some shavers, aren't that sophisticated. They use a thing which looks just like a plugpack, but actually has a basic circuit inside to control the charging of a battery. They can be hard to recognise, but they will usually have a strange voltage and/or current output - for example, 16.85V, 350mA. Unfortunately, these kinds of chargers can be very difficult to replace. Your best bet is likely to be to read the section below about stepdown transformers, or contacting the manufacturer for a replacement that works in Australia.

Other devices to be powered in a car
If your device needs 3, 4.5, 6, 7, 9 or 12V at <1A you can buy a plugpack type device from the usual places which plugs into your cigarette lighter and has the replaceable tips same as other plugpacks. If it's a laptop, refer to the above. If it's a bigger device, or a direct mains powered device, you'll need an inverter. An inverter plugs into your cigaretter lighter (or connects directly to your battery if it's a high powered device) and delivers 240VAC (or 110VAC if you need to power such devices and buy a US/Japanese inverter from ebay) to a standard wall socket type outlet. Most small electronics, simple AC motors, lights, heaters, soldering irons, etc will run just fine from a standard "modified square wave" type inverter. These can be purchased in various power capacities, rated in Watts (W). Check your device's specs for its power rating, or multiply its current rating in amps (A) by 240 to get a rough estimate of power needed, and get the next bigger one. Many things, like big motors, compressors, refridgerators, etc, can have low current requirements, but have very high surge currents - when you first turn them on, they suck huge amounts of power, then settle down to a much lower level. Most inverters list their available surge power, but the devices usually don't. Ask the manufacturer of your device, or a sales assistant where you buy your inverter if it will be okay. If in doubt, you can have a punt, but be prepared to replace your fuses or even your inverter. If it's a really big surge current, it might be best to look for another solution (eg, it's usually better and cheaper to by a proper 12V fridge than try to buy an inverter big enough to power even a small bar fridge).
Some devices won't work happily with the modified square wave output supplied by the cheap inverters. These include "light dimmers, variable speed drills, sewing machine speed controls and some laser printers" as well as laptops and other large switchmode power supplies, or particularly sensitive, medical or test equipment. In these cases, you can buy a pure sinewave inverter, just be aware that these are more expensive, and it may be worth looking for another solution.

Devices which charge from a USB port
The electronics suppliers also sell plugpacks for mains or cigarette lighter use which have a USB port on their outlets. You can plug a USB cable into these and it will charge your device as though it was connected to a PC - in many cases, it will charge faster because USB ports have a lower current capacity than these packs. There are some exceptions to this rule, though, as some things only start charging when they get connected to a PC and start communicating with the operating system, in which case you're stuck with a PC or laptop.

Non-standard and proprietary connectors
Many devices have connectors which can't be found amongst the standard set of plugs supplied with the replacement plugpack. In some cases this appears to be just because the manufacturer obtained a cheap supply of odd plugs. In others, it's a deliberate attempt by the manufacturer to force you to buy their own replacement parts, or throw the baby out with the bathwater and buy a whole new device. Whatever the reason, it can make it tricky to replace the power supply. If you're in a Jaycar shop, they'll usually have a box of connectors under the counter that you can root through to find a matching plug. If there's not one there, sometimes you'll be able to purchase a matching plug off the shelf - for example, some supplies use a minidin connector, similar to s-video or PS2 plugs, which you can buy as spare parts. In this case, you'll need to cut the end off your replacement plugpack, and solder the wires onto the pins. You'll need to work out which pin is which first, though. If you have the US plugpack, or you're buying a replacement for a pack that failed, you can cannibalise it for the connector. Cut the end off it, and if you're lucky the wires inside will be clearly identified - eg red for positive, black for negative. Just solder them onto the positive and negative wires in your new plugpack. If you're trying to use a laptop in your car and you have a functioning mains plugpack with a non-standard connector, you can make up an adapter from it. Buy a 2.5mm DC plug and socket off the shelf. Cut the end off the mains supply, and solder the 2.5mm socket onto the wires from the plug, then solder the 2.5mm plug onto the wires from the power supply. Your incar plugpack will then have a 2.5mm plug which you can use - the little adapter stays plugged into your laptop, and you use the car or house supplies which now both have matching plugs.

If you do not have soldering tools and experience, you'll need to take it to a friend who does, or a local appliance repair shop to get this work done.

If all else fails...
If for any of the above reasons, or any other reason, you're unable to replace your plugpack with a suitable Australian model, you may require a stepdown transformer. These plug into an Australian 240V outlet and deliver 110 or 120V on their outlets, which is suitable to power most US or Japanese devices. There are some caveats though - Australian power is at 50Hz, US is at 60Hz, and you can't change that. Most things don't care what frequency their power is, but some things do - most notably bedside alarm clocks, anything which uses the frequency of the mains supply to trigger internal timing functions, or some types of AC motor. If that's the case, you're probably sunk, and need to put it back on ebay while looking for an Australian version. If that's not a problem, or you don't think it will be, you can buy a stepdown transformer but make sure it has a higher power capacity than your device needs - multiply the current required by 120 for an approximate answer.
If you can't find a stepdown transformer to suit your device, or one with a high enough rating costs ten times what you paid for the device, put it back on ebay and sell it to someone else, then buy locally - it might be more expensive than the US version, but not once you factor in a 1000W stepdown.
One last possibility exists. PC supplies often have a switch which selects 100/240V operation. Some other devices (for example, I've seen a few amplifiers and DVD players like this) have separate internal connections for 110 or 240V operations. You may have to open the device and disconnect the mains from one set of pins marked 110, then plug them into another set marked 240. There may be a transformer inside with similar markings on its outputs. You'll be pretty lucky if yours is like this, though, and even more lucky if the markings are clear and its easy to figure out what needs to be changed. Only even consider attempting this if you're experienced with working on 240V, have read the 240V sticky at the top of this forum, are a licensed electrician and a Fellow of the Royal Australian College of Surgeons (what the hey?).

Further reading
Inverter technology and applications here.
More discussion of plugpacks, including how they work here.
Please post any other useful references and I'll include them here.

All the Jaycar links are fine LethalCorpse but the DSE needs fixing.

Edit: Ignore me the DSE one is fine. Just didn't load for me first time. Weird.

Nice job there, it needed to be done, I'm far too lazy to write one up

Now we just need this sticky'd

thx LethalCorpse great write up :D

Great article!

I love DC power but I don't like plug packs or wall warts as the yanks call it. A few years ago I decided to use an old 350W ATX power supply and get rid of the plug packs as all of them lined up create quite a bit of heat which isn't nice in summer. I replaced the fan in it with a quiet one and put it on a shelf inside behind the drawer of my desk. I went for the ATX one because it supply's 12V and 5V for my needs.

It runs my desk lights I installed (replaced CCFLs with LEDs last week) a 8 port network switch 12V, IP camera on 5V and a cordless phone charging dock which originally takes 9V but has been fine on 12V (I decided to take the risk).

I use to run more off it but I had a sparky install a AC outlet in the roof. I moved part of the home network to there. I now have a server rack up there with a GME 13.8V regulated DC power supply that can supply 6A continuous (11A peak). I originally got it to run off my UHF radio but wasn't enough. The good thing about it is that it has no fan so it should be fine in a dusty roof inside a cabinet.

In the roof I run another 8 port network switch 12V, a NAT/router/wireless access point 12V. Soon I'm going to install a regulator so i can supply 5V from the roof and the IP camera will be powered from that instead.

I run and charge a lot of things from my main power supply which is a powertech one with volts and amps readout on the front. Output is 3V to 15V 40A and is a big beast around the size of an Xbox.

Earlier this year I purchased a UHF handheld with charger dock from America and the plug packs input was only 110V AC so I chopped the plug off and hooked it up to my radio power supply... easy done!

Great stuff :thumbup:

I went to set the sticky, but someone else has beat me to it...

Thanks for the comments guys. Glad you think it's useful :)

Thats post 3000 for you too.

I've got a plugpack question, and I felt it was best suited to ask in here.

I want to drive a 120mm PC fan to make a fume exhaust unit. I have plenty of old Nokia jack chargers, but they aren't marked. Can I use my DMM to determine whether they output AC or DC? And if they are AC, what circuit do I need to build to convert it to DC?

they should all be DC, so you should be fine just hooking it up

Hardly 1.7A for a plug-pack powered device.

(shaped like a cloverleaf)

multiply its current rating

That was a real example. They've overrated te inut requirements, but switchmode supplies do have stupidly high peak loads. Fixed the two typos though

15 amp Plugs

I have just purchased a Deep Fryer which has a 15 amp plug. Can i just get a plug adaptor or do i need an electrician to change the powepoint

It's worse than that, it'll need to be on a dedicated circuit. Call a sparky and get him to quote, but it will almost certainly cost more than the fryer.

This thread, by the way, is totally the wrong place for this discussion

Here's a nice guide I just stumbled upon
http://digital-diy.com/General-Electronics/ac-dc-power-supplies-using-wall-warts.html

Often you can replace an AC power supply with a DC one. The reason for this is that the AC usually gets regulated to DC inside the device. Usually use a lower voltage. e.g. replace a 15V AC with a 12V DC.

Don't go the other way because that hardly ever works and you're likely to damage something.

Yes, it is sometimes possible that the device has an internal rectifier, which means either ac or dc will work. There is no way to tell that by looking at the unit though, and if you're wrong it'll probably blow up.

You've got the sizing arse backwards. An unregulated, rectified and filtered ac supply will give a higher dc voltage than what's written on it, up to its rated current. So a dc pack would typically be higher voltage for the same purpose, but how do you decide how much bigger?

Meanwhile, in the world where switchmode supplies are much cheaper than transformers, the only reason to supply an AC pack is if the device needs it -ie it produces positive and negative rails inside or uses the AC frequency for timing. It can't do that with DC.

This is a one-size-fits-all guide, and it is always safer and usually cheaper and easier to go buy the correct replacement.

Came back to this topic by chance and so I though i'd write a response...

That's true about the unregulated, rectified and filtered ac supply giving a higher dc voltage than what's written on it a lot of the time, especially under low loads.

An unregulated dc supply will also give a higher voltage than what is written on it if the load is low. The process of rectification from AC to DC drops the voltage. Typically you would go for a lower voltage DC supply (with the same current rating), to have a better chance of avoiding damage to the device.

As for blowing up something by using a DC plugpack instead of an AC one, it is unlikely. There are two main situations where it doesn't work that could happen in the real world.
-The first would be that the device needs AC to do timing. In that case the device most likely will do nothing when fed with DC. This will cover most situations.
-The other situation would be that the device uses transformers to convert to other AC voltages. Be more wary of this with audio gear like old guitar effects pedals. In that case you may damage the device. Although if you only try it for a couple of seconds you probably won't! So test for a couple of seconds and if it doesn't work then no harm done.

Generally things that require AC actually have a mains transformer built in to them in the first place. With smaller things that run from plugpacks it doesn't matter most of the time if you give it AC or DC.

These days we typically don't have to worry about these things so much thanks to cheap switchmode supplies becoming the norm, but 10 years ago when switchmodes were still expensive there were still many devices that came with an AC plugpack rather than a DC one. Probably because it was the cheapest way to do it at the time (skimp on a few diodes etc). Typically you will see it on cheap devices or budget brands.

Also, don't try giving DC to an AC motor. Fortunately most AC motors are not run from plugpacks.

So far the devices for i've replaced AC plugpacks with DC ones over the years have been these:
-Routers
-Modem
-Portable CD player (ran very hot when I gave it the same DC voltage)
-LCD Monitor
-LCD TV

All worked perfectly when supplied with a plugpack rated at a lower DC voltage than the AC plugpack they used to run from. Most of them came with a generic, cheapo 15VAC or 9VAC plugpack.

As LethalCorpse said, it's often easier to get the correct replacement and if you don't know what you're doing then do that to be safe.

These days AC plugpacks tend to be quite expensive compared to cheap switchmode DC ones, so you can save quite a bit if you know what to do.

Hope this info is all helpful. Here's some more info on the topic:
http://www.ti.com/lit/an/slyt126/slyt126.pdf
http://www.afrotechmods.com/videos/diode_tutorial.htm

it's not particularly helpful. Refer to my previous post.

you should read my post and the links i posted, then go beyond that and further research it online. your post is misleading.