5V output circuit

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Hi all,

I need a basic circuit with an Output of 5V, It should run off two 1.5V
AA batteries. Thanx!

 

[PeteS]

Hi all,

I need a basic circuit with an Output of 5V, It should run off two 1.5V
AA batteries. Thanx!

Your homework assignment would probably have specified the output
current required of this circuit. amongst other things (ripple, noise,
step response to name but a few).

Cheers

PeteS

 

[Jamie]

Hi all,

I need a basic circuit with an Output of 5V, It should run off two 1.5V
AA batteries. Thanx!

look for DC-DC converters.
you can get them already made in mods..

 

[jasonbot]

I'm making a USB charger so I'm not to sure about all the deets All I
know is that it should output 5V or else the device will blow..

 

[mc]

I'm making a USB charger so I'm not to sure about all the deets All I
know is that it should output 5V or else the device will blow..

How much current do you need to deliver?

 

[jasonbot]

How much current do you need to deliver?

No Idea, however much USB needs??? Think it's either 100 or 500mA

 

[jasonbot]

No Idea, however much USB needs??? Think it's either 100 or 500mA

EDIT: device (iPod) needs 500mA of power 100mA is not enough to power
it.

 

[Don Bowey]

EDIT: device (iPod) needs 500mA of power 100mA is not enough to power
it.

A correct USB port will source 500 mA.

Don

 

[Roger Hamlett]

A correct USB port will source 500 mA.

This is more complex than it seems. Any device that requires more than
100mA, is meant to 'ask' the system if it can have the extra. Most USB
ports _will_ supply 500mA, without such a request, but quite a few will
give 'overcurrent' errors, if a device tries to draw this, without first
getting the approval...

Best Wishes

 

[jasonbot]

So the theory is there but what will the circuit diagram look like??

 

[mc]

So the theory is there but what will the circuit diagram look like??

OK, you want 5 V at up to 500 mA from two AA cells. That will run down the
AA cells fairly quickly, but not absurdly quickly... I don't know what the
battery life will be.

Since you're stepping up the voltage, this has to be a switching regulator,
probably with an inductor (of carefully specified type) in the circuit.
That is not nearly as easy as stepping the voltage down.

See this data sheet:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1327
And this:
http://pdfserv.maxim-ic.com/en/ds/MAX641-MAX643.pdf

 

[Walter Harley]

OK, you want 5 V at up to 500 mA from two AA cells. That will run down
the AA cells fairly quickly, but not absurdly quickly... I don't know what
the battery life will be.

Energizer Alkaline AA lists 2850mAh nominal capacity at C/100, that is, at
25mA.

But 5V at 500mA is 2.5W; assume 70% efficiency from a boost converter
home-made by a beginner, so the batteries need to supply about 3.6W total.
Each battery supplies half of that power, so the draw is 1.8W/1.5V = 1.2A
when the batteries are charged, going up to 1.8W/0.8V = 2.2A at the
nominally-discharged point.

From the curves at http://data.energizer.com/PDFs/E91.pdf one can see that
drawing around 2A is much higher than the battery is rated for, and
substantially reduces its capacity. Extrapolating from those curves I'd
guess the actual capacity at that rate is somewhere around 500mAh, meaning
the batteries will last about 15 minutes. Probably not enough for a charge.

 

[mc]

....
From the curves at http://data.energizer.com/PDFs/E91.pdf one can see that
drawing around 2A is much higher than the battery is rated for, and
substantially reduces its capacity. Extrapolating from those curves I'd
guess the actual capacity at that rate is somewhere around 500mAh, meaning
the batteries will last about 15 minutes. Probably not enough for a
charge.

I wonder if he really needs 500 mA. What will this be powering?

 

[jasonbot]

I wonder if he really needs 500 mA. What will this be powering?

I want to power my iPod Video, USB 2.0 device, technically it should
use 500mA, maybe not. I've seen other designs on the internet using
2AA's powering the iPod for at least 3hours.

 

[petrus bitbyter]

I want to power my iPod Video, USB 2.0 device, technically it should
use 500mA, maybe not. I've seen other designs on the internet using
2AA's powering the iPod for at least 3hours.

 

[petrus bitbyter]

I want to power my iPod Video, USB 2.0 device, technically it should
use 500mA, maybe not. I've seen other designs on the internet using
2AA's powering the iPod for at least 3hours.

Well, there's an easy way to find out. Get some 5V power supply and a mA
meter.

petrus bitbyter

 

[jasonbot]

Well, there's an easy way to find out. Get some 5V power supply and a mA

meter.

lol, First I need to MAKE a 5V power source???

 

[mc]

I want to power my iPod Video, USB 2.0 device, technically it should
use 500mA, maybe not. I've seen other designs on the internet using
2AA's powering the iPod for at least 3hours.

Then it definitely does not consume 500 mA all the time.

The Maxim chip that I mentioned earlier is probably the way to go. There
are not any large differences in efficiency between different chips of that
general type.

 

[petrus bitbyter]

lol, First I need to MAKE a 5V power source???

Not necessarily but that's what I should do if I hadn't one already. You can
try to borrow one or use it at a school lab. You can even buy a 5V wallwart
or a 9-12V type and connect a 5V regulator to it. But one thing is for sure:
If you want to make something with nothing you will end up with nothing.

petrus bitbyter

 

[jasonbot]

The Maxim chip that I mentioned earlier is probably the way to go. There

are not any large differences in efficiency between different chips of that
general type.

The maxim chip seems great but maybe a little complex, I got my ideas
from here:
http://www.instructables.com/id/EGBQJPLCB2EP287KTZ/#CEVEIRM4776EP288H78

And would now like to expand on the idea, I dont want to buy the kit
because I want to marvel at my own design, I have a basic idea but now
need to put th eplan into action. How woul 4 AA's 6V with a regulator
compare with the 3V step up, the 6V would be much easier.