transformer 110 to 240

mystraightroad wrote: :

at

is

Yes.

12

Yes.

No. But why buy a transformer to power an adapter? Just but a 12V 3A adapter for 230V input. Maplins sell 'em.

thank you so much for your replies.

Ok, I have a feeling this is a stupid question but here goes....

If we assume that the draw is twice the max output (75w) would it hurt if I were to use a transformer rated at 300w rather than one at 100w. A friend has said they will lend me a 300w transformer, I'm just concerned it might be too strong.

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Yes, but the round pin is, arguably, on the bottom.

Yes, the round pin is earth ground, it should be connected to the chassis of your device. Your output can supply 36 Watts. You didn't say what the device is. I suspect a power supply for something. Without any more information I can only guess that your 45 watt adaptor will be fine. Regards, Tom

>

you said the appliance at 12v draws 3 amps = 36watts if you now supply it with a 300watt supply you have enough power to connect about 8 of these devices.

A transformer cannot be too strong, but it can be too weak. In the trade, acquiring items with greater ratings than minimum is called "pro-rating." If you use the 300VA - it's more correct to use the term "Volt-Amps" (VA) when speaking of AC power - your design will be just fine.

Here's a very good article that discusses just the subject you are concerned with:

Have at it, sparky!

Yes.

Correct.

Just buy a power adapter with a 12 Volt output capable of at least 3 Amps. For example if you buy a 48Watt adapter with a 12V, it can suppy a maximum current of 48/12= 4A. So you can connect any 12V device, and draw a MAX of

4A. There is no minumum draw, your 3A device will work fine, so will a device rated at 12V and 2A or 1A or 500mA, etc...

Dwayne

go to your local electronic supply store and get your self a AC(240 Vac) to DC (12volts DC)converter that will supply 3 or more amps. in the long run, it will be cheaper and easier for you.

It will work just fine, however, power losses (nothing works with 100% efficiency) will be slightly higher. For something used only sporadically that's nothing to worry about.