Advice on DC power transformer

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robjg63

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#93415 21-Nov-2011 10:28

Hi,
I wonder if someone can give me some advice please.

I have a device that needs a 9V DC power source - it can use batteries (6 x 1.5 AA batteries) - but batteries get to be a pain.

It says on the device that it needs 9v then it says 850mA.
I think the one that the manufacturer will proved as an expensive accessory is apparently 500mA.

I tried a Dick Smith adaptor (regulated) that can output 9V - it said it was 500mah and the device worked fine - I dont want to use that adaptor though.

I have found an adaptor that is 9v and says its "OUTPUT:9V 1000mA 9VA"
I would guess the last A probably refers to Adjusted? (ie regulated)

Now assuming I get the polarity correct (Thats my issue of course), am I right thinking that the 1000mA just means it *can* output up to 1000mA if required. So assuming the device uses less it wont hurt it.

Nothing is impossible for the man who doesn't have to do it himself - A. H. Weiler

RunningMan

8953 posts

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#547748 21-Nov-2011 10:36

The 9VA is volt-amps.

It is quite possible this is outputing AC not DC, so you would need to confirm that first.

RunningMan

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#547750 21-Nov-2011 10:38

Oops, clikced the button too quickly...

Having said that, you are correct about the current - the current listed on a power supply is the maximum that it can supply, but the device will only draw what it needs.

The voltage and polarity must match though.

robjg63

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#547765 21-Nov-2011 10:59

Thanks RunningMan,
It has that symbol - the line with the 3 dashes underneath - That seems to be the symbol for DC.
It also says its an AC-DC Adaptor - So I think I am ok on the DC.
But thanks for the current advice.

Nothing is impossible for the man who doesn't have to do it himself - A. H. Weiler

RunningMan

8953 posts

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#547796 21-Nov-2011 11:54

Excellent - you should be fine then. Generally they will also say if they are regulated or not - whether this matters depends on the specific equipment being connected...