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5V regulated power supply with 4 1.5V batteries ??

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aviv6371

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7805c high current

hi ,

i want to build a regulated 5V with 200ma current supply with only 4 batteries of
1.5V size AA.

any suggestions ??

any suggestions using AAA batteries olso wellcomed.


avi.
 

namqn

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5v power supply with step up converter

That is possible.

Look for some LDO (low-dropout) voltage regulators, such as LT1529-5 (5.5V minimum input voltage, 5V output, 3000 mA output).

Cheers,
 

throwaway18

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5v regulated power supply

To make use of all the available energy in a dry-cell battery you need to use them down to 1.1V per cell.

You can use a switching regulator.
 

aviv6371

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1.5v regulated stepup converter

thanx, what are the disadvantages of using 4 1.2V AAA batteries??

avi
 

xxargs

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5v dc from 1.5v battery

throwaway18 said:
To make use of all the available energy in a dry-cell battery you need to use them down to 1.1V per cell.

You can use a switching regulator.

Hmm. if remember rigth standard 'emty' dry/akaline battery is 0.9 Volt/cell -> 3.6 Volt for 4 cell-pack.


For 5 Volt logic-supply You need switched voltage converter going in buck-mode with fresh battery and smothly going to boost mode with half to empty batterys. or you in same situation as old digital camera needs new batterys in short time and 'used' replaced battery have more than half capacity remains + user cannot use NiMH-batterys in your power hungry equipment (1.2 V/cell * 4 = 4.8 Volt)...

Other way, use boost switcher to make 8-10 Volt from batterys 3.6 - 6.4 Volt and next step using buck switcher to make wanted 5.0 Volt. (if you want high power and high quality loadspeakers/ear-phone drivers without clipping in high level - you want more than 5 Volt to feed this drivers...)

or design your equipment for 3.3 Volt logic...

for more easy design - use 6 cell battery pack and make buck switcher power supply can handle from 9.6 Volt (fresh alkaline batterys) to 5.4 Volt (empty battery as 0.9 Volt/cell) and also make possible to use NiMh-batteries.

---

Is hard but possible to find few app-notes to bulid switches can work both in buck and boost mode depend if input voltage is higher or lower compare to output voltage - look on Maxim, Linear technology, National semiconductor etc. appnote library.

(I look long ago for simular problem as unstable 12 Volt car-batterys (6.5 Volt with start engine to near 16 Volt charging voltage in cold weather) to stable 12 Volt for example feed computers and harddisk.)
 

yousafzai

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1.5v dc transformer

Try the DC-DC converter from "MELCHER" they are good
 

deepu_ttc

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how to make 5v from 1.5v

hello friend i think you can do it. as far as i know with use of i/p filter ckt +buck regulator+o/p filter can do this

try it i think it will do well
pradeep
 

angelote

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5v - 1.5v power supply

I agree with throwaway18.
To use the whole energy from your battery pack, you should use a DC-DC converter.
There are converters that work in buck mode when battery voltage is over output voltage, and in boost mode when it's below output voltage.
Yor output current is low, so you'll find a single-IC solution. But remember to filter output to get your ripple requirements.
With that kind of DC-DC you can use 1,2V batteries withot problems. If you need high currents from battery, I don't recommned you to use NiMH; it's better to use NiCd or Li+ for rechargeable and high current purposes.
 

waterman

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use DC-DC Switching Regulator, step-up type
 

fenugrec

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If you need good regulation & efficiency, you can combine a step-up switcher and an LDO. For example, you could use a REG104-5 (5.0V, 1amp (or 1.5 ? can't remember) LDO regulator by TI) fed with the simplest step-up converter you can find, and isolate that so you don't get all the switching noise in the rest of the circuit.

Christian
 

aviv6371

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hi guys,

thanx for the good will but i think i m little confused with all these advises .

can i use 6 1.5V and 7805C which can give me 200ma needed for the circuit????

do i need to use heat sink for the 0.8Watf max power dissipation on regulator ??

avi.
 

roofingboom

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go to power.ti.com and under device quick search click on view additional crietera
next fill in vin min as 4.8 and win max as 6 then output 1 as 5v and .2 a
Two integrated switch controllers and two external switch controllers will show up.

TI had great app notes and i am very resource ful so check out those ccontrollers and you should be set. If you have anyquestions feel free to ask
Thanks
hope you find a solution!
 

fenugrec

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Do you *have* to use a 7805 ? There are so many better chips around...
 

Beowolf

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aviv6371, don't be scared by the DC-DC converter. The reason that all of us is forcing it is efficiency. If you use 200mA of current, you will drain 6 AAA cells in 4-6 hours. In the mean time, you will waste around 25% of it's energy on heat in 7805.

As for the recipe, I would use only two cells, and a step-up converter. If you need more juice, use 2x2 cells (two in series paralleled with another pair).
 

aviv6371

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i think i will take beowolfs advise. can anyone guide me to a good and cheap
step up converter. is max667 good enough for that purpose ???

**broken link removed**

thanx in advance

avi.
 

kender

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aviv6371 said:
i think i will take beowolfs advise. can anyone guide me to a good and cheap
step up converter. is max667 good enough for that purpose ???

MAX667 is as far from the step-up converter as it gets - it’s a linear regulator. :) Take a look at MAX756. Also, keep in mind that step-up converters are more expensive than linear regulators, because they require an inductor and a relatively large capacitor. However, in your case the step-up converter will quickly pay for itself by saving lots of batteries.

By the way, do you have any rf components in your device (such as radio modem, Bluetooth, GPS etc)? I’m asking, because one of the caveats of the switchers is the EMI, although there are ways to block it.
 

Beowolf

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Motorola MC 34063A is good and cheap. I designed (not tested yet) a 1.1"x1.1" PCB single sided with 3 pins connector so it can be put instead of 78xx. And as a bonus, it's reduced EMI. (coil is 1" away from the pcb).
 

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