# Voltage source for Arduino based circuit

Hello everybody,

So I am doing a project, where all sensors with Arduino Uno itself draws about 310 mA of current. I need a battery, that will last without recharge about 8 hours conected to my circuit. As I calculated, the battery should be 2500 mAh. But what voltage should I use? 9, 12 V with voltage regulator connected, or something else? All the sensors use 5V.

Thanks!

2S LiPo configuration (7.4v) unless something needs a higher voltage. The linear regulator on the Uno dissipates the difference between input voltage and 5v as heat, so you want the voltage as close to the output voltage as possible while still being high enough to get the necessary output voltage (the regulator has a bit over a volt of dropout). 7.4 is a common voltage, since that’s what you get from 2 LiPo’s in series.

Cheap EBay 18650 batteries do not come within a mile of meeting their spec (I have some “5300” mAh 18650’s that do like 800 on a good day, and some “9800” mAh batteries that don’t even hold 500). So don’t use them - either use a 2S pack made for the RC hobby crowd, or 2S stack of matched top-shelf panasonic 18650’s or something.

The linear regulator on the Uno dissipates the difference between input voltage and 5v as heat, so you want the voltage as close to the output voltage as possible while still being high enough to get the necessary output voltage (the regulator has a bit over a volt of dropout).

Okay, but then the current through Arduino regulator will be: 1,5W/(7,4-1-5)V = 1.07A. And the regulator can output max 0.8A. Am I wrong? Will not this burn it?

Current through a linear regulator is equal to the current required by the load.

You're going to dissipate around 1W though, that may be too much to run without overheating, at least without taking mitigating measures.

Use a micro-power buck converter between the battery and the 5volt pin. Then you can use a 2S, 3S, 12volt car, or whatever battery economically. This buck converter will draw less than 150mA from a 12volt source when powering a 5volt/310mA Arduino setup. https://www.pololu.com/product/2843 Leo..

https://www.batteryclerk.co.uk/yuasa-np6-6-6v-7ah-emergency-light-battery.html?gclid=CNa74ZromtMCFYoK0wodJrYCiw

Do you really need to use a LIPO. ?

Do you really need to use a LIPO. ?

Sorry, but 6 in battery is too big. It is a paragliding project :(

Thank you all, I will use Li-ion 3 batteries, each 3.7 V with L78S05CV voltage regulator :)

Why three. One battery will be just be there to heat up the regulator.

As DrAzzy already told you, use two. Best to power through the DC socket. Leo..

Well, he can't use 2S with that obsolete voltage regulator - L78S05CV requires 8v input! THREE VOLTS OF DROPOUT! That's just awful; straight out of the dark ages. Even a normal 7805 will get you 5v from 2S LiPo! A 7805 would work just fine here, as would a 1117-series regulator; 1117's are my go-to regulators, preferably the ZLDO ones, though every manufacturer has their own near identical take on the 1117)

Not sure why OP wants to use such a lousy regulator; I advise against it.

With anything that has less than 2.4v of dropout at 310mA as regulator, a 2S configuration is strictly better than a 3S configuration - the extra voltage is entirely wasted as heat, resulting in increased heatsinking requirements on the regulator for absolutely no increase in battery life. (ofc, with a switching regulator, it's a different story)