# Power up 2 circuits in parallel with one source

Discussion in 'General Electronics Discussion' started by armadon, Dec 24, 2014.

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Dec 24, 2014
Hello all, sorry for my poor english, it isn't my native language,

I have a problem, probably really simple, I have 2 circuits that I try to power up in parallel one of them take a tension between 9 and 12 volt and the other one take 4.5 volt, and I was wondering how I could do to use only one source, so I was thinking about putting the 2 circuits in parallel and use a zener diode to regulate the voltage of the circuit that take 4.5V but I am not sure about how I should put in place that circuits and how to use the zener diode to regulate the voltage.
Any help is welcome, thank you in advance.

2. ### davennModerator

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Sep 5, 2009

welcome to EP

OK, you have told us what voltage each of the 2 circuits requires, what current does each circuit need ?
What are the circuits and what is the power supply ?

answer those questions and people will have a better idea what to suggest

cheers
Dave

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Dec 24, 2014
One of the circuit has a max Amp of one. I cannot say for the other one but it normally use three AAA battery.
I was thinking about using two 9V battery, to have 18 volt.

One of the circuit is an Arduino and the other one is a headset that I use to get data for the microcontroller.

Hope that it could help.
-A

ps:And I have another weird problem with the arduino but I don't want to abuse of people time.

4. ### davennModerator

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Sep 5, 2009
OK those small rectangular PP3 9V batteries have very little current capability and wouldn't be able to supply 1Amp for any length of time
Does this project need to be portable ?

no problem there .... we have a section of the forum for micro controller questions
start a thread in there describing the problem in good detail and see if some one can help
( its not my field of interest)

Dave

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Dec 24, 2014
Well yes it does need to be portable but I could use AA or AAA batteries, I wonder how I could efficiently share the tension between those 2 circuits without having the one that take 4.5V burn.
And I'll post another thread of the arduino problem after that, thanks

6. ### davennModerator

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Sep 5, 2009
you can use a voltage regulator off the higher voltage rail to supply the lower voltage rail, that's the easy part

you are going to have to consider your power supply and requirements , that's going to be the harder part

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Dec 24, 2014
I did some research about voltage regulator. So if I understood well, I could take 2 rechargeable 9V battery to don't ruin myself. I've checked and even if the amperage is lower, the arduino runs smoothly with a 9V battery. Well I have made a schematic, terrible one but I hope you could understand it.

Edit: After some researches, I've seen that for voltage regulator, 4.5V was uncommon, but the headset looks to work with 5.2V so I guess I could take the 5V regulator as long as it doesn't go above this tension.

Last edited: Dec 24, 2014
8. ### BobK

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Jan 5, 2010
Why would you want to use 18V when the max voltage you need is 9V? All that does is waste half the power immediately.

I know the Arduino boards take 9-12V but they actually run this through a voltage regulator to get 5V for the microcontroller. Is there a 5V input as well on your board? You could probably run both devices off 5V.

Bob