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Regulator Current
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Please be positive and constructive with your questions and comments.

Regulator Current

by bman22 on Sat Feb 28, 2009 9:54 pm

I have been working with pretty basic circuits for a long time. Recently, I got the MINIPOV3, and that got me a bit more interested in the microcontrollers area. Now, im trying to make a pretty basic device, that will display something on a character LCD. Only issue is that the lcd i happen to have, is a 3.3v, which means i need a regulator. I found a bunch of regulators online, but i have no clue how to figure out how many mA i need. i have the ATTINY2313-20PU, which says it takes 230 uA, the lcd, from what i have read is probably 20mA, and an optical sensor that is 50mA. How do i calculate what mA output i need. And, because all of the lower mA are SMD's, can i get one of the high amperage rated through-hole ones without burning out anything?
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Re: Regulator Current

by westfw on Sat Feb 28, 2009 10:33 pm

because all of the lower mA are SMD's, can i get one of the high amperage rated through-hole ones without burning out anything?

Yep; your circuit will only take what it needs. Cheap three-terminal 1A T-H regulators are your best bet, though I'm not sure what the favorite is at 3.3V (you could get a bunch of lm317 variable regulators and set it up for 3.3V with a couple of resistors; those will cover a lot of space.)

Aside from large physical size, the old, large regulators are likely to have a large-ish quiescent current (current consumed by the regulator itself; something like 5mA for a 7805-style regulator), so you need to be more careful in your searching if you're trying for a low-power circuit...
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Re: Regulator Current

by bman22 on Sat Feb 28, 2009 10:59 pm

Great. Im not particulary interested in a variable regulator. i would really prefer to keep it simple. And by no means am i looking for a lower power. I will most likely be using a wall adapter. Also, say i were to get a 1amp regulator. How much current should i be giving it. I know it needs to be more, but i dont know how much

edit:
http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMuLLNXTG1MZauOVzvKLoYtg0cHsuAb2R78%3d

This should do the trick correct?
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Probably not your best choice

by Ran Talbott on Sun Mar 01, 2009 12:06 am

For many years, 3-terminal TO-220 voltage regulators were made with an "input-ground-output" pin configuration.

The LD1177V33 has a "ground-out-in" configuration. For convenience (e.g., if you want to build an Arduino boardf for 3.3V operation), you probably want to get regulators that match the old standard pinout. Such as:

http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMuLLNXTG1MZajswaupnmlqk%252bc6mLVEzVbI%3d

http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMuLLNXTG1MZauOVzvKLoYtgDADt3TT0NOI%3d

http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMuLLNXTG1MZari5y6DWRJldMnV44NeQC7w%3d

(Note: these are all low-dropout, and only rated at half an Amp. If you don't need LDO, or need more current, I believe there's a 78M33 that's comparable to to other 78xx TO-220 regulators).

I just got burned on this: I just bought some of those very chips recently, after failing to notice the differing pinout. Luckily, I'd also bought a few TO-92 regulators, so I was able to use a couple of those as a temporary kluge until I get some TO-220 ones ordered.

Ran
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Re: Regulator Current

by westfw on Sun Mar 01, 2009 1:21 am

For convenience (e.g., if you want to build an Arduino boardf for 3.3V operation), you probably want to get regulators that match the old standard pinout.

Check the actual regulator on YOUR arduino board. I believe that the diecimila and later (with SMT Low-Drop-Out regulators) have the "new" style pinout, while at least some of the freeduino boards use an SMT 7805 with the old pinout, for example.

(I believe that it's due to physics. LDO regulators end up having their power transistor substrate (pin 2, heatsink tab) connected to Vout, and traditional regulators ... don't.)
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Re: Regulator Current

by bman22 on Sun Mar 01, 2009 3:25 pm

no, i don't have an arduino. I went with the LF33CV though. If any of you could look at my other post, it seems to being ignored, and the code is really what i need help on. Its under microcontrollers
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Please be positive and constructive with your questions and comments.