Hi I've recently purchased some electrical appliances that came from America, as such the appliance requires 110-120V power. Is there anywhere that is recommended to go for a step down transformer in NSW? Otherwise I'll jump down to the nearest Jaycar or Dick Smith Powerhouse if they still exist…
EDIT: It is an inflatable mattress with a built in air pump. Voltage is 110-120V, Frequency is 60Hz and Amperage is 0.9A.
I always just find a plug that fits and takes the input voltage.
i.e. no point going from 240-110-12v if you already have a plug lying around that does 240-12v
You are talking about an AC to DC plugpack which provides 12 volts DC, the OP was asking about an AC to AC stepdown transformer which provides mains 120 volts AC.
You need to be very careful to get one that handles the wattage. Many are designed for shavers etc. Generally the higher the wattage, the higher the price.
It's not as simple as a step down converter, depending on what you are using. If it is a 50hz device, your converter will only supply 60hz. Any device with a clock in it as part of its computer will run too fast. If its an alarm clock, it won't keep accurate time, if its a TV it won't work at all because the image will roll up the screen constantly. The only way to fix this is to step up then step down, a really expensive and probably noisy proposal.
It's 60 there and 50 here. Stepping up and down or the other way won't change the frequency, unless there is an inverter involved.
It would need to be a reasonably primitive device that relies on mains frequency for its clock these days, most have internal circuitry to generate their own accurate clock. I haven't seen a modern TV that isn't multi-voltage tolerant; it's cheaper to build one power supply for global consumption than build one for each country. All that is necessary is to supply a different local power cord. Modern TVs won't roll in the way you describe either, I haven't seen that phenomenon since black and white cathode-ray tube days, when they had a vertical hold knob. Again, they generate their own clock to prevent exactly this behaviour.
It would be more helpful to advise precisely the type of device you are using, as the advice will change depending on the situation. Some things won't care about the mains frequency, but you are likely to kill them by putting twice the voltage through them (e.g. light globes, some motors, heating elements…). More sophisticated appliances (TVs, laptops etc) generally have intelligent power supplies and can take care of the global differences in mains power. Generally all that is required is a change of plug/cord. But if you don't know the difference and get it wrong, it can be an expensive and dangerous mistake.
… most have internal circuitry to generate their own accurate clock.
I'd be a bit inclined to leave out the word 'accurate' there…
Since the advent of cheap & nasty quartz-crystal substitutes (many years ago now), the accuracy of so many cheap (and not-so cheap) watches and devices with internal (non network-updated) clocks, remains crapulent.
The very first VCR I bought had a mains frequency regulated clock and kept nigh-on perfect time. Never more than a second or two off.
The near-to-last VCR I bought didn't. It still lives (plugged in on standby - if I don't get around to digitising those remaining tapes soon, It'll never happen…).
Just had a look at the time display - running 18 minutes fast…
I also have a slightly less ancient HD set-top box that still lives (and cost a bomb when new). Front panel clock doesn't get (digital) network-updated - for some stupid reason - and it's way-off too.
Both, and others, irk.
Me like accurate clock.
Grrr!
Well there are clocks and there are "clocks". I'm not talking about the cheap ICs they use to run RTCs (real-time clocks to tell time of day), that usually generate their own timing. I'm referring to the frequency clock generating accurate ticks (in the order of 70 nanoseconds to draw a "pixel" on a PAL TV, and to line up scan lines so they all accurately start drawing at the right time and therefore the same position on the screen. If the timing were off by as much as one "pixel" the result would be strikingly obvious with lines being drawn all over the place. So the reference clocks are pretty accurate, usually within a few nanoseconds, because they need to be. As for the RTCs, there are many reasons for them to be way off. Usually because they are cheap. And BTW, the mains frequency isn't foolproof, it does fluctuate from time to time.
@endotherm:
I was specifically riffing off the reference to mains-frequency and its use in the past, in and of itself, as the most simple of timing references.
Mains-frequency used to be extremely tightly controlled. There is indeed a little more 'leeway' displayed from power suppliers now.
Voltage fluctuations a little wilder too, although not too bad in Qld - at least relative to W.A's appliance-killer days of yore.
Poor Sandgropers - they used to have contend with Great White Sharks and killer voltage spikes…
It is an inflatable mattress with a built in air pump. Voltage is 110-120V, Frequency is 60Hz and Amperage is 0.9A.
Does it have any kind of power supply or wall wart that supplies low voltage to the mattress, or does the mains go straight into the mattress (shudder!)? If the former, all you have to do is get a power supply that has the same or better low voltage side capacity. If the latter, you need a 100VA step down transformer, and if the mattress has an AC motor, it will run at 5/6ths the speed.
Luckily it is only a motor driving a pump, so there shouldn't be any complex electronics to worry about. Assuming it is a mains powered motor, and does not have a transformer or plugpack hidden away inside to bring it down to low voltage DC, you could probably get away with a simple unit. My late-night maths tells me you will need 108 watts or more. You would probably be stressing a 100W unit, so go with a 200-300W unit. There are a few on eBay from NSW for $30-50 delivered, some with twin outlets.
e.g. http://www.ebay.com.au/itm/200W-240v-110v-step-down-transfor…
http://www.ebay.com.au/itm/step-down-transformer-300w-350w-s…
Do you have a link to the actual mattress so we can determine if it is a mains pump or a low-voltage pump?
By the way, maths aside, there is this to consider:
Stepdown transformers need to be down rated by 30% when used with inductive loads (motors)
So your 108 Watt requirement becomes around 140 Watts when dealing with your pump.
@endotherm: Thanks for the recommendations. http://www.ebay.com/itm/INTEX-Ultra-Plush-Queen-Raised-Airbe… that is a link to the item that I purchased. I think I will get the first one that you linked to as I have one of these in 'queen' size and one in 'double' size.
It will depend on the appliances.
I've got myself a cheap $10 step down at bcf. Good enough for my water flosser.
Nice find, that's a pretty good price for one of these, and good enough for a small appliance like you have described. Otherwise it would be like using a Karcher in your mouth :) if it didn't burn out first.
I take it you got this one: http://www.bcf.com.au/online-store/products/Korjo-Step-Down-…
Unfortunately it is rated at 210mA and my appliance is rated at 900mA so it seems like a no go… Unless… I create some sort of parallel circuit???
We should probably all spare a thought for the OzBargainer some time back who unwittingly purchased a several-hundred-dollar 110 volt Dyson vacuum cleaner online and was bereft as a result of their stupidity. It was an expensive mistake.
They were trying to resell it. I wonder how they fared.
OP, otherwise or just wattage-wise, I hope you haven't been that silly as regards the items you've purchased from the U.S.
I did come close to buying an eBay auction item from a American seller once - before the voltage-penny dropped late. Buyer beware, etc…
Got one from ebay for $65 in 2012.
Search "240v 110v Step Down Stepdown Transformer 1000w Watt".
Did you get a NutriBullet? ;-p Looked into this for that as the American NBs are over half price.
Saw some stepdowns on eBay for around $100. There are dual ones, two power slots.