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[fokus_1116]

hi,
may i ask..if i wan to use battery to replace the power supply, what battery to recommend?

[mackrackit]

hi,
may i ask..if i wan to use battery to replace the power supply, what battery to recommend?

That is a difficult one to answer.
The VDIP requires 5 volts. Four re-chargeable "AA" batteries will give ~4.8 volts, close enough but for how long. Then if someone were to use regular batteries now there is ~6 volts present, not good, the MCU will "smoke".

Could use a 7805 regulator with a ~9 volt or higher battery pack but then you need to carry around a "brick" of batteries. And the 7805 requires a heat sink and is not the most efficient thing out there, reliable yes... LM317 could also be used but has some of the same problems.

You may want to use a switching regulator. Could have one that works with a battery input from 3 to 6 volts, then four "AA" batteries of any type will work. Depending on the circuit the efficiency can be very good.

Not knowing the load of the finished project, you may not know yet either, the best I caqn do is point you here
http://www.national.com/analog
Look at the "WEBENCH DESIGNER". Input your parameters and see what come up.

I have also hear some talk about off the shelf DC to DC converters.

[Byte_Butcher]

That is a difficult one to answer.
The VDIP requires 5 volts. Four re-chargeable "AA" batteries will give ~4.8 volts, close enough but for how long.

Be cautious with your battery types here... 4 NiCad AA's will give about 4.8v, but 4 rechargeable ALKALINE AA's can give over 5.6V +

For linear regulators, these aren't too bad...
http://ww1.microchip.com/downloads/e...Doc/21991c.pdf
Only a couple hundred mV dropout voltage, so they work OK on 5 v circuits from a 6v battery.

You may want to use a switching regulator. Could have one that works with a battery input from 3 to 6 volts, then four "AA" batteries of any type will work. Depending on the circuit the efficiency can be very good.

If you need to run off a wide supply range, including sucking batteries down "to the last drop" then a good switching supply is THE way to go....


steve

[Dave]

Byte_Butcher, Where do you find rechargable ALKALINE AA's ? I have never heard of such a thing.... I'm curious...

Dave Purola,
N8NTA

[Byte_Butcher]

Byte_Butcher, Where do you find rechargable ALKALINE AA's ? I have never heard of such a thing.... I'm curious...

/Cough/ err... well, they do exist, and a quick google search should find you some. But I was MISTAKEN about the ones that I have. I was sure it said Alkaline on the package when I got them, but on closer inspection, these say NiMH on the side of the battery.

So I guess I meant to say that" 4 rechargeable NiMH AA's can give over 5.6V +" Sorry...

steve

[mackrackit]

What is the brand of the NiMH and AH of the batteries you use?
The NiMH I use are 1.2 volts at 2500 AH.

[mackrackit]

OPPSS!
That should be 2500 mAh