Assistance/Help needed designing 3A / 12V power supply

Hello Arduinians -

Looking for some assistance with my current project. I have googled around, but am either finding too many different answers, or not the correct information for my application. I apologize in advance for the n00b questions.

I am currently controlling a 12v fan from a GPIO pin (on/off not speed) using a MOSFET circuit. The fan uses about 6 watts of power @ 12 v (580mA).

My ultimate goal is to control 8 various fans for a total of which will draw 40 watts of power (3.3 amps). There is one other part of my circuit, not related to the fans, which requires filtered 12V on the power supply of an op-amp.

The (stupid?) questions are how do i design, or acquire a power supply capable of delivering 12v @ 3.3 amps for the fans and also filtered 12v for my op-amp?

I have a bunch of LM7812 IC's one of my thoughts was to wire 4 in parallel, 3 for the fans and 1 for the rest of the op-amp but i do not know if that is even possible or reccomended so i haven't tried that. I found a few components like this, however i am not really sure this is the correct choice for my application, they seem expensive, and not clear on how filtered it is for the supply of the op-amp (is this where an RC comes in?)

Any help is appreciated! Thank you


Well, there are a number of choices. You could use an old PC supply. Here's an Instructable to show you how: Or you could buy a new one. Here's a source with a good selection of affordable supplies: How much filtering you need for your opamp is going to depend on your application although for most purposes I would think any regulated supply should work.

Use your web search and search for power supply schematics. Will give you a lot of info.