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# how to make a 240v 2A dc power supply? Answered

i need a 240v dc power supply for a project but my pablum is ,i need to reduce the current up to 2 amps
i know how to reduce the voltage but how i can reduce current ?

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## 6 Replies

rickharris (author)2017-05-02

Can you tell us WHY it needs to be current limited to 2 amps.

In general items draw the current they need. If your wanting a safety limit put a 2 amp fuse in line with the supply.

rickharris (author)2017-05-03
Jack A Lopez (author)2017-05-02

Perhaps mains power, plus a simple rectifier circuit, half wave, or full wave, etc:

https://en.wikipedia.org/wiki/Rectifier#Rectifier_...

Then put that in series with one or two incandescent light bulbs,

https://en.wikipedia.org/wiki/Incandescent_light_b...

for to effect your current limiting.

I mean, what I have described is the, uh, "cheap and dirty" way to do this.

Actually, for not much more cost, you could throw in a TRIAC based lamp dimmer,

https://en.wikipedia.org/wiki/Dimmer#Solid-state_d...

to sort of throttle the mains power, and give you AC with less RMS voltage before the rectifier stage.

Regarding cost, cheapness, if you have ever gone shopping for a power supply, you might have noticed price tends to scale with power capacity. So that a little 5W thing to charge your phone is really cheap, and a 30 W brick for charging a laptop is maybe moderately priced.

When I multiply the two numbers in your spec together, I get 480 W, and that is kind of a big number. So there might be some sticker shock, if you actually go shopping for, and find offer for, a professionally made 240VDC, constant voltage, with 2A max current, power supply.

iceng (author)2017-05-02

+1

Excellent answer...

Vina should realize a current limit operates by lowering the voltage when you start to draw over 2 amperes...

Downunder35m (author)2017-05-02

Be aware though that at these levels DC will be deadly to the touch....

iceng (author)2017-05-02

I have twice survived 240 VAC across my chest..

Once got my hand frozen to an arcade gun game after swimming my feet were bare and wet. This occurred at a girls basement with a dangerous faulty un-grounded limited motion metal pistol target game.

The current froze my muscles to the grip and I could not even call for help..

Eventually I was able to release my left leg enough to fall down which pulled my hand loose from the current source.. I was an EE at the time and twice warned the family of the lethal game !

The girls father was totally unconcerned of the danger in his home and I later stopped dating her.. No idea what ever they did about my warning..