3-Terminal Regulator question

3074 Views 16 Replies 4 Participants Last post by micromind, May 21, 2009

Robertw55

Discussion Starter · May 20, 2009 (Edited)

i have a charger that I use for my PSP that is 300mA and 4.5v.

The PSP is 5v 2A

this charger isn't the real charger for the PSP, it just happens to fit and it works fine (just takes longer).

im making a charger out of small 1 watt solar panels and using a +5v 1A 3T regulator. So would it be ok to use a +5v 1A charger for the 5v 2A? That wont damage my PSP right? charging under the specs?

also, will it damage a 5v 1a 3 terminal regulator putting 2.5 amps into it from the solar panels? Or is it specifically made to reduce amperage as well?

many thanks

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Robertw55

Discussion Starter · #4 · May 20, 2009 (Edited)

sorry, im a newbie and a bit confused.

So feeding the electricity to my 5v 2A PSP from a +5v 1A 3T regulator isn't a good idea? i thought it would be ok since the voltage is the same. also, i thought because the 3T regulator is feeding 1A into the 2A PSP, it would keep it undercharged, but still be ok. i just wanted to confirm it. hopefully this makes sense.

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Robertw55

Discussion Starter · #6 · May 20, 2009

just saw the post from micromind after i posted last.

it is a 7805

when you say the chip needs a heatsink, are you talking about the chip inside the PSP? if so, how would i know if it has one?

so i don't need to worry about the battery being Ni-Cd and Nimh because the battery is 2A and the charger is 1A right?

again sorry if these are stupid questions

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Robertw55

Discussion Starter · #9 · May 20, 2009

i truly appreciate all the information, could you possibly show me a link of what this heatsink would look like so I don't get the wrong thing. and the ground you are referring to is that end tab with the hole cut out of it right? thanks again

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Robertw55

Discussion Starter · #11 · May 20, 2009 (Edited)

thank you kindly micromind and everyone else.

i'm not seeing a 3" x 3" on mouser.com, I'm seeing numbers like 36.83 mm L x 17.17 mm W x 21.59 mm H and 0 1.75 in L x 0.375 in W x 1.45 in H. does that basically mean this particular site doesn't have the one I need?

I googled and tried to find a 3" x 3" TO-220 but no luck. is there a more specific size I need for the 7805, or do I just need to look harder to find a 3" x 3"? thanks

also, as far as the white greasy compound, would I still use that? if so what is it called and who would I apply it?

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Robertw55

Discussion Starter · #12 · May 20, 2009

another thing,

will I damage the 5v 1a regulator putting 2.5 amps into it from the solar panels?

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Robertw55

Discussion Starter · #14 · May 20, 2009

thanks, but i'm still trying to find out what size heatsink i need for the 7805. there are so many to choose from and i dont see a 3x3.

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Robertw55

Discussion Starter · #15 · May 20, 2009

would this one work?

http://www.radioshack.com/product/index.jsp?productId=2102856

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Robertw55

Discussion Starter · #16 · May 20, 2009

ok, so i figured out that i need a heatsink to dissipate 40watts because I'll be sending 32V, 2A (from the small solar panels) through a +5v 1A 7805. (so that link to the heatsink in my last post wouldn't work)

how would I search for a heatsink to dissipate 40 watts? i googled "TO-220 40w heatsink" but no luck)

if someone could please refer a link to a heatsink that would fill these requirements I would be greatful. i've been searching on google for 3 hours now and the more i look at, the more confusing it gets.

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