Ant_Magma said:

I'm looking for a transformer that is capable of stepping down 240V

from the wall outlet to maybe less than 20V depending on the type of

voltage regulator. My objective is to produce 3.3V from the wall outlet

to power my ICs.

1) Most of the times i see 2 same values for the secondary voltage, eg:

0-9,0-9 (9V). What does it mean? Does it mean i still get 9V output?

2) If i want to calculate the output current, do i take the power

rating lets say 3VA and divide with the output voltage, for example 3VA

/ 9V=0.33A?

power is power, if the device can only deliver 100 Watts for example,

that is what you get .

when you scale down the voltage you simply get higher current at the

lower voltage which can still work out to the same max watts.

if you know the wattage of the supply source via the label on the

unit? then you can calculate the amps you will expect to get .

Watts/Volts = Amps.

so if lets say your little step down supply is 100 watt handling and

you have 9volts, the current should be a little less than 11 amps/.

i say a little less is because of other factors that come in when using

something like a xformer. you have losses and efficiency factors.

that is about as basic as i can get it.