How to Power Arduino Uno & SIM900

Projects General Guidance
1

Hi there,

I've been working on a project that is basically a garden sensor that uses a SIM900 mini module along with an Arduino Uno which has a variety of sensors hooked up. The sensors are plugged into 3.3V, and the SIM900 is plugged into 5V. As of now, I'm just using power from when I plug the Arduino into my computer. The SIM often has trouble uploading data because it doesn't have enough power.

Since I want to be able to place this project outside, I want it to be solar powered. In order to do that, I need help choosing solar panels to use. I would also think a lipo battery of some sort connected to the solar pannel(s) would be useful, so that the project can run during the night or when it's cloudy.

Does anyone have any suggestions for how to power it?

Thanks!

2

You could use a solar panel connected to a powerbank. You'd be best off with a 0.25m2 solar panel.

If you use a big enough powerbank (depending on your amp draw and powerbank size) it could last up to nine days before it needs to recharge.

3

How big do you think this solar panel would be? I'm going for something as small as possible.

4

@rocketlyy

It will be 25 centimeters square. But don't go connecting the wrong voltage solar panel to it! It must be 5v.

5

Uhhh, lemme think about that.

A power-hungry 50mA Uno and a cellphone module (2A peak) might need that 0.25m2 panel.
It all depends where you live. Panel current strongly depends on sunlight.
Panel output could drop to 5% on an overcast day.
My 10*10cm panel can just keep up with a 20mA LED night light on an overcast winter day.
On a sunny day it will take less than 20min to re-charge that battery.
Leo..

6

Yeah, true. That data is perfect for where I live. I'm in Australia.

If you have a big enough battery backup (30000 mah), you should last 600 hours without recharging.

7

Don't forget that powerbanks state the capacity of the internal 3V7 battery.
The boost process to 5volt means more input current is needed for a given output current, and there are idle losses. Expect 2/3 of those values.
Did you already work out that 0.25m squared is 2500cm2?
Leo..

1 Like
8

@Wawa
Yes. I've been doing research for a somewhat complex high-amperage (1000ma) project whaich has to last on battery for a minimum of 24 hours. So I'm getting a 30000mah power bank so the extra 6 hours can be too low voltage and all that. Technically, it should run for about 27 hours reliably.

I was just relaying that info to @rocketlyy.

9

You need to re-visit your primary school arithmetic notes @outbackhut .

A 0.25m2 panel would be 0.5 m square. (1/2 x 1/2 = 1/4)

A 25cm (0.25m) square panel would be 0.0625m2. (1/4 x 1/4 = 1/16)

10

@glittering_owlet
:rofl::rofl:
Thanks mate!
Yes, it's obvious when you tell me that.

I'm definitely not a mathematician....

11

Do you think that’s the smallest size I can use to power everything? I’m trying to keep the entire project as small as possible, and since I need to disguise the sensor (I’m going to make it look like a rock), I’m trying to make sure that I can keep it compact.

12

As hinted before, it's not going to end well with a power-hungry Uno and a small solar panel.
Leo..

1 Like
13

Okay good to know. In that case, do you recommend any other boards to use that would use less power but still do the trick?

14

Google "Arduino low power".
A 3.3volt 8Mhz ProMini (or a naked Atmega328) seems to be the best choice.
Leo..

15

You could also do a whole bunch of clever stuff to make your uno take nearly nill power...

16

Yep, with a lot of hacking you could turn your Uno into an 3.3volt 8Mhz ProMini.
Leo..

17

@Wawa

18

You must have seen that the Uno with all the hacking still uses more than a ProMini without it.
Leo..

1 Like
19

Yeah. It would depend what the OP is doing and how much hardware is connected.

20

OP has maybe unrealistic expectations of running an Arduino controlled cellphone module with LiPo battery and charger (not optional) from a small solar panel. That requires mA currents from every single part. Not an easy task. Expect you can harvest <10mAh from a small 160mA solar panel.
Leo..

1 Like