240V - 12V or 5V

Im Aussie so its 240V but if you use a different power level you should still have the same problem.

How can i take a 240V source and convert it to 12V or 5V without noise.

By noise i mean is the hum of a transformer.

Its only small but when you expect places to be quiet and there is a hum in the background it makes it hard to go to sleep.

Anyone have any ideas?

Mosfets or BJT's seem like the way to go, basic chopper circuit. Then a few caps to smooth the voltage.

For low currents many of the common 'wall wart' power supplies can be the solution. Every one that I've ever used is silent. For larger supplies and possibly one you'd build yourself then I would guess that a high quality transformer might be the solution - if you build it yourself. An alternative might be a computer power supply.

A reasonably well-made transformer won't hum.

My wallwart supply hummed like crazy :cry:

If you want a cllllleeeeean supply, im sure that the PSU out of a computer would suply a very very clean 12 and 5 volts.

The 'better' wallwarts these days are switch-mode, so can't possibly hum 8)

zachtheterrible said:

My wallwart supply hummed like crazy

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I don't doubt it, but "A reasonably well-made transformer won't hum."