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FenceFurniture
3rd May 2016, 10:04 PM
Does it matter about the Amps rating on a wall wart? Is the voltage the most important factor?

I've had a plethora of new devices arrive from the States recently, and of course the adaptors/WWarts all have two parallel prongs. If the WW supplied is say 12 volts and 500Ma draw can I use another with Oz prongs that is 12v and say 2A? Or will it cause damage. To my non-electronic brain the current draw would be limited by what the device will draw - a bit like using 15A rated power cable for a machine that will only draw 10A.



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Luke Maddux
3rd May 2016, 10:17 PM
I think you may be right about the Amps thing. You can plug a 10amp machine into a 15amp power point (is that what a Wall Wart is??) and it will run fine.

So with that said, yes, I believe voltage is the key factor with regards to the performance of the implement you plan to plug into the wall.

A couple of things though...

When I moved down here I had a US soldering iron. The first time I went to use it, with a plug converter, it heated up super quick and then kind of went -zzt and that was it. Game over. I think some things don't really regulate the amount of voltage they use and will just overwork themselves and fry out with a quickness.

The other problem is with frequency. I may have this backwards, but I think we use 60Hz in the US whereas everyone else uses 50Hz, so your item may run to a lesser degree because of that, even though the voltage is higher. I think it depends on the item. While you can regulate voltage with step up and step down devices, my understanding is that you cannot change the frequency.

I probably just made that confusing...

This sounds like a BobL question.

Good luck,
Luke

Bohdan
3rd May 2016, 10:18 PM
You are correct. As long as the output voltage is correct and the current rating exceeds the original it will work without doing any damage.

Picko
3rd May 2016, 10:22 PM
What the devil is a wall wart? This is the second time in a week that I've seen this here.

FenceFurniture
3rd May 2016, 10:26 PM
The black lump that plugs into the wall to take 240v down to something the device can handle (think phone charger).

A Duke
3rd May 2016, 10:29 PM
Hi,
The output V has to be correct and also the same AC or DC, and if DC the polarity must be correct ( + - )
Be easier to get an adapter plug Aus to USA and use the original provided it is 240V input.
Regards

Luke Maddux
3rd May 2016, 10:32 PM
The black lump that plugs into the wall to take 240v down to something the device can handle (think phone charger).

Not sure about the ones where the plug itself is a big black lump, but things like laptop chargers, where there is a cable between the wall and the black lump, work fine.

BobL
3rd May 2016, 11:21 PM
I've been collecting and measuring the outputs of wall warts and adapters for around 20 years and have some 3 shoeboxes full of these things. The first thing I noticed was the claimed voltages don't always coincide with the actual output. Eg nominal 12 V walwarts ranged from ~10 to 16V. The quality of the output varies enormously, from RAG half wave rectification through to very smooth outputs. Computer power adapters tend to be better than most wall warts.

Some gear is more sensitive to the actual V and some are not happy about poor quality rectification.

FenceFurniture
3rd May 2016, 11:47 PM
Not sure about the ones where the plug itself is a big black lump, but things like laptop chargers, where there is a cable between the wall and the black lump, work fine.I don't think there's a difference there Luke. The cable just provides a way for the manufacturer to make the wart universal (different cable end for different countries).

Luke Maddux
4th May 2016, 07:21 AM
I don't think there's a difference there Luke. The cable just provides a way for the manufacturer to make the wart universal (different cable end for different countries).

That was my assumption as well, so maybe that means you're ok?

I have several American laptops, all of which have just been retrofitted with Australian leads from JB Hifi. Never had a problem in four years.

NCArcher
4th May 2016, 08:15 AM
Most warts are multi voltage, designed to work on American 110 or European 220 (no-one designs anything for Aus voltages. We don't count) The input side is designed to handle the largest voltage and the output side has a voltage regulator which will keep the output within a few volts of whats required.
I have lots of Chinese wall warts with dodgy US/Aus adapters. Throw away the adapters they "give you for free" and buy a half decent one. If you have lots, a US power board with an AUS plug is a good way to plug them all in safely.

Yanis
4th May 2016, 10:26 AM
I've been collecting and measuring the outputs of wall warts and adapters for around 20 years and have some 3 shoeboxes full of these things. The first thing I noticed was the claimed voltages don't always coincide with the actual output. Eg nominal 12 V walwarts ranged from ~10 to 16V. The quality of the output varies enormously, from RAG half wave rectification through to very smooth outputs. Computer power adapters tend to be better than most wall warts.

Some gear is more sensitive to the actual V and some are not happy about poor quality rectification.

Yes correct Bob. A ... let me call it by its proper name, power supply or PSU is not nearly as simple as it appears and depends on what it is powering.

In the old days they were simply transformers with (posibly) no regulation. They may deliver 15V open circuit but when you plugged them into the device they were designed to power the voltage dropped to say 12V or there abouts. Of course for more delicate electronics the output was regulated, that is it was electronically controlled to supply a constant voltage regardless. Since then the technology has changed a LOT but you can still get the old fashioned transformers with or without regulators but there are many more options.

Now skipp to today and what is required from a PSU depends a lot on what you are powering. Smart phone chargers for instance use fully electronic PSUs (switching for those of a technical bent) delivering 5V pretty precisely with either 500mA (1/2 A) 1A or 2.2A depending on the exact phone. This is effectively the same voltage and currents you get from your USB port. This makes it relatively simple. So if you get a replacement phone charger (genuine or third party) with the USB style outlet you can be pretty well guaranteed that your 5V out will be well regulated up to the stated current.

On the other hand the PSUs that you get from your Chinese gadgets may very well be all over the place. Transformer (heavy) electronic (light) unregulated, lots of electronic hash (radio interference) poorly regulated. As I said it all depends on what it is powering and the quality of the product.

In general it is a good idea when you buy a PSU that you match the voltage and ensure that the current rating matches or exceed the current required by the device. However, and this is a huge caveat, whether it actually runs the device depends on the type of device and whether the PSU is electronically compatible with the device. Where the PSU is designed for the device type you will be fine but don't be at all surprised if the PSU does not run the device.

Take LED lights for instance. The circuit inside the low voltage LED light is quite complex and requires a PSU that is capable of driving the lights. The wrong supply can destroy the lights or PSU, or just not work. Also a cheap supply can produce electronic hash and interfere with radio receivers.

Sorry if this is a bit technical but it is not really a simple subject.

John

LanceC
4th May 2016, 11:21 AM
I've been collecting and measuring the outputs of wall warts and adapters for around 20 years and have some 3 shoeboxes full of these things. The first thing I noticed was the claimed voltages don't always coincide with the actual output. Eg nominal 12 V walwarts ranged from ~10 to 16V. The quality of the output varies enormously, from RAG half wave rectification through to very smooth outputs. Computer power adapters tend to be better than most wall warts.

Some gear is more sensitive to the actual V and some are not happy about poor quality rectification.

Note that to get an accurate reading you need to test the voltage under load. Otherwise it will generally show a higher voltage. Regarding quality, I generally try an use ones that are double shielded and filtered for audio circuits or where electrical nose is a factor. (the symbol with one box within another).

Like you I too used to collect the things so I'd have one on hand for whatever, until I discovered that the local dump shop has a massive basket of them for $1 each. Saves me having to use up space at home.

FenceFurniture
4th May 2016, 12:08 PM
Ok, a case in point now. I have an external BluRay player for my laptop. The wall Wart has an American slide off plug which can be exchanged for any other type of plug, but I can't easily get hold of one. I need to use the DVD player immediately to install some software (can't be downloaded from the net).

So, the WW that comes with the device is 12v DC 3A. All I can get from the local Jaycar is 12v DC 2.5A. Will that be ok? Would it be likely that some headroom is built into the original 3A WW and that it probably won't draw 36 watts? Or will the 2.5A WW get a bit hotter?

I will look around on ebay to try to get a proper sliding Ozzie plug replacement, but I can't wait any longer for that to arrive from wherever it may come from.

Luke Maddux
4th May 2016, 12:15 PM
Can you not just get a plug converter? The cheap things they sell at BigW or airports or even some convenience stores?

Yanis
4th May 2016, 12:26 PM
Can you not just get a plug converter? The cheap things they sell at BigW or airports or even some convenience stores?

If you use the pin converter then make sure that the plugpack is rated up to 230V. Some are universal and some are specifically 110V.

John

FenceFurniture
4th May 2016, 01:01 PM
Well it seems to be working ok, and the wart isn't hot at all. The plug converter available is MASSIVE and will take up too much space on the power board.