L4931

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Dalolin
Posts: 3
Joined: Mon Jan 19, 2009 11:21 am

L4931

Post by Dalolin » Mon Jan 19, 2009 11:32 am

Hello :D

I got my RBBB last week and im going to build a nightlight for my nephew, and use it for other projects once I find more things to make with it!

But my question is, can I use a 6v 2amp center positive power brick with the L4931 or should I use a LM7805?.

Im new to electronics so im not sure how much current the L4931 can handle, I know it outputs 300ma but I couldn't find the max it can handle? I hope that makes sense :?:

Thanks!

paul
Site Admin
Posts: 764
Joined: Mon May 12, 2008 4:19 pm

Re: L4931

Post by paul » Mon Jan 19, 2009 11:40 am

As long as the center is positive on the power supply, it will work fine.

You are correct about the regulator - it will only put out around 300 mA so that will limit what you can hook up to the RBBB. A 7805 is not ideal with a 6V supply because it requires about 2.5 V dropout. I've got some 2940's that are LDO's (low dropout regulators) if you need a higher current output.

If your power supply is regulated (be sure about this) you could also run without a regulator, as the Atmega168 will tolerate 6 volts.

Paul

Dalolin
Posts: 3
Joined: Mon Jan 19, 2009 11:21 am

Re: L4931

Post by Dalolin » Mon Jan 19, 2009 11:51 am

Quick reply! thanks!

I have no idea if its regulated or not (it says switching power supply). I'll stick with the L4931 for now though.

Thanks again!

Severian
Posts: 14
Joined: Thu May 22, 2008 5:48 pm
Location: Texas

Re: L4931

Post by Severian » Thu Apr 23, 2009 1:25 am

Howdy,
Look at the label on the power supply, if it has one. If it shows two horizontal lines where it shows the power capacity, it is unregulated. If it shows a solid line on top and a dashed line below, it is a regulated supply.
Good luck,
Ralph

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