12V DC power supplies question

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wallop

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Ultimate Geek

#121089 24-Jun-2013 15:14

I need a 12V 100ma DC power supply. I'm having trouble finding one so I'm wondering if I can use a 12V 400ma? Is that going to cause problems i.e. is the ma rating important or will the device just draw what it needs from a over rated power supply as long as the volts are the same?

Thanks

wallop

ubergeeknz

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Vocus

#842428 24-Jun-2013 15:18

So long as it's a regulated supply, the current (A or mA) rating of the power supply needs to be the same or more than what is required by the device you're trying to power. It doesn't matter if it's more so long as the voltage is correct.

Unregulated supplies tend to run a higher voltage with loads less than the rating, so in that case YMMV.

wallop

367 posts

Ultimate Geek

#842435 24-Jun-2013 15:28

Thanks, in that case I think Jaycar has what I need.

ubergeeknz

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Vocus

#842437 24-Jun-2013 15:31

Cool! One more thing: be real sure to hook up the polarity correctly, or the smoke will almost certainly escape from your device.

wallop

367 posts

Ultimate Geek

#843419 24-Jun-2013 15:49

Will do. Last thing I need is smoke, the missus would not be happy.

Niel

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#843439 24-Jun-2013 16:25

There is one exception, some battery chargers (e.g. for cordeless phones) rely on the power adapter doing current limiting but most switch mode power adapters (not all) will hiccup instead of limit, and also their threshold is about 10-20% above their rating. What do you need it for?

You can never have enough Volvos!

wallop

367 posts

Ultimate Geek

#843470 24-Jun-2013 16:45

It's for a remote control extender. http://www.hot-link.com/pages/products.cgi?mrchcatid=1&mrchid=11 It's from the states and the included power supply is 120volts input.

richms

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#843656 24-Jun-2013 21:46

You will probably be fine with anything from 7.5V up on something like that. The use of a grotty transformer based 12v one is a US solution to voltage sag which is a massive problem over there on unregulated supplies on their half strength power.

Richard rich.ms

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DarthKermit

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#846041 27-Jun-2013 12:02

Hello, I had a look through my collection and have found a plug in 12 volt DC transformer, output of 100 ma. Would you be interested in it?

Whatifthespacekeyhadneverbeeninvented?

wallop

367 posts

Ultimate Geek

#846045 27-Jun-2013 12:06

Thanks for the offer but I got one from Jaycar.

wallop