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constant 4.5 V supply using batteries? Answered

how may i get a constant power supply of 4.5 Voltusing batteries?

--------------------------------------------------------------WHAT I FOUND SO FAR

googling and visiting several discussion groupsi found related advice ...
- e.g. using 1 more than the required batteriesin combination with e.g. a voltage regulator, diode, resistor, DAC -

if i use 4 instead of 3 aa batteriesand the voltage drops after a while -
would a voltage regulator, resistor, DACstill provide 4.5V from the remaining voltage?

may i ask you what you would recommend?
--------------------------------------------------------------WHAT I NEED IT FOR

i am using rf sender/receiver modules
with my picaxe 08m microcontrollers
&
found, that they (and the connected antennas)
work best at a constant voltage of 4.5 V

7 Replies

user
luxstarBest Answer (author)2012-09-02

Here is an instructable using a DC to Dc converter:

 

 

 

https://www.instructables.com/id/93-efficient-DC-to-DC-Converter/

The data sheet says the input voltage can be 4.5 to 14 volts. The output can be adjusted from one half volt to 6 volts. If you used this converter and upped you input voltage to 6 volts it would work fine. Bit if you added more batteries and / or larger batteries like 7.5 to 9 volts you could have some serous run time without the inefficiency you get with a linear regulator. Murata makes several different devices for different current / wattage requirements;

 

 

http://www.futureelectronics.com/en/Search.aspx?dsNav=Ntk:PlainTextSearch%7coktr%7c3%7c,Ny:True,Nea:True

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user
marc_is_curious (author)luxstar2012-09-10

thanks for the hint -
this sounds like a good, prefabricated solution
that requires a minimum input of work on my behalf
&
i can even use just another 1.5 AA in addition to my 3 AA's
to get a constant voltage of 4.5!

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user
Re-design (author)2011-10-19
user

thanks sean & re-design ...
bigger in that case seems to be better indeed ... i've been told to use a capacitor on top of the voltage regulator in order to avoid signal interferences with the circuit;
so this might do the trick ....

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user
Prfesser (author)2011-10-19

Yes, you could use four AA cells instead of three, and the voltage regulator would keep the voltage nicely at 4.5 V. The bad news is that when the voltage of a cell drops significantly---by more than a tenth of a volt or so--- that cell is very near the end. So you would probably get a little more time out of a set of batteries. Whether three cells for a period of time, or four cells for a bit longer, is better must be decided by you, in your particular application.

Good luck!

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user
marc_is_curious (author)Prfesser2011-10-19

thanks, Prfesser ... this is valuable information - did not know that!

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user
seandogue (author)2011-10-19

It sounds as if the thing you're hooking to your power supply are drawing enough curent that you're depleting your batteries quickly.

There are three solutions:

1. Reduce the power drain of your circuit (whatever you're connecting to the power supply)

2. Use larger capacity batteries, to offset the fast drain

3. Carry lots of AA batteries as backup.

I'm a fan of both 1 and 2, but under certain circumstances, #3 isn't an unreasonable solution.

A more comprehensive solution might also consider the efficiency of your power supply, but that's probably not an answer in itself.

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