Powering the Core module

[LetterBeacon]

The ucapps website specifies using a 7-10VAC transformer to power the Core module. I have a 12VAC transformer lying around - can I just use that? What's the reasoning behind specifying 7-10VAC? Is it the heat given off by the regulator?

I'm planning on using the Smash TV Core PCB which has the regulator mounted on the side of the PCB meaning I should be able to get a decent sized heatsink on there. By my calculations, giving the regulator 12VAC it will dissipate 3.5W, so by using a 8.8C heatsink (which I also already have) I should be able to keep the regulator at a safe temperature. Does this sound like a good idea?

EDIT - The 7805 datasheet says the maximum voltage is 35V, so ucapps specifying 7-10VAC must be for heatsinking reasons, right?

Edited November 8, 2009 by LetterBeacon

[lylehaze]

The ucapps website specifies using a 7-10VAC transformer to power the Core module. I have a 12VAC transformer lying around - can I just use that? What's the reasoning behind specifying 7-10VAC? Is it the heat given off by the regulator?

I'm planning on using the Smash TV Core PCB which has the regulator mounted on the side of the PCB meaning I should be able to get a decent sized heatsink on there. By my calculations, giving the regulator 12VAC it will dissipate 3.5W, so by using a 8.8C heatsink (which I also already have) I should be able to keep the regulator at a safe temperature. Does this sound like a good idea?

EDIT - The 7805 datasheet says the maximum voltage is 35V, so ucapps specifying 7-10VAC must be for heatsinking reasons, right?

Yes, you can use 12VAC.

Yes, it will be hotter that way.

Yes, A bigger heatsink will take care of that.

You seem to be up on your math.. :)

Of course you understand that 12VAC will rectify to something greater than 12VDC,

and exactly how much higher is not just math, but depends on the specific transformer you choose, and how the manufacturer rated it.

Personally, I have a lot of PIC18F boards used in industrial settings that are powered off 24VDC.. using just a 7805 and an ample heatsink.

They do get warm.. :)

Oh, and Welcome to the Midibox forums!

Have Fun,

LyleHaze

Edited November 8, 2009 by lylehaze

[LetterBeacon]

Thanks for the reply!

I'm planning on using the Midibox inside my modular which is in quite a big open backed case, so there is a fair bit of air flow that'll help the large heatsink do its thing.