SMALL Battery Ideas For LED Control, Arduino Mini

I am planning a project and I need to know what I should get as a power supply. I haven't purchased any of the parts yet so I don't know yet weather I will use the 5v pro Mini or the 3.3v pro min, that will depend on what kind of battery supply I can get.

What I am building is basically a gauntlet (lower arm and hand armor) with a "jewel" on the back of the hand that will light up. I will push a button that will cause one LED to glow stead at a dim light(caused by a higher resister) and another LED that will be brighter but will blink on and off ( to make it look like it is pulsing). That will go one for exactly 1 minute and then shut off. Also I want another button to just make both LEDs come on solid and go off when I press it again (not for very long, maybe a couple minutes.

I need a battery that will power this and go for about 3 days, being used for 1 minute spans at least once every 6 hours. the battery also has to be relatively safe as it will be attached to the inside of the armor, but still probably put in a protective case (as well as the Mini) Battery can be rechargeable or non-rechargeable as long as they don't cost an arm and a leg.

Any other pointers on this project would also be appreciated as I'm new with Arduinos.

Thanks in advance :slight_smile:

Sounds like something a 3-pack of AAs or AAAs and 5V promini can handle, powered from VCC pin (bypassing the 5V regulator), and not the RAW pin 9.
Or a LiPo battery (4.2V dropping to 3.7V) and 3.3V promini, still powered thru the VCC pin. Check www.adafruit.com for different capacities.
Here’s a 1000mAH LiPo for example

would your first example with the 3 aa or aaa batteries also work with an arduino nano v3.0?

I also have a phone battery from a broken phone that is 3.7v 1400mAh with limited charge voltage 4.2v, would that work? or would it not because the nano is 5v?

CrossRoads:
Sounds like something a 3-pack of AAs or AAAs and 5V promini can handle, powered from VCC pin (bypassing the 5V regulator), and not the RAW pin 9.
Or a LiPo battery (4.2V dropping to 3.7V) and 3.3V promini, still powered thru the VCC pin. Check www.adafruit.com for different capacities.
Here’s a 1000mAH LiPo for example

Do you have any idea how ridiculously OVERKILL that is?

Let’s just spitball some numbers here. I’ll just guess that both LEDs might take 50 mA total to run at adequate brightness. The microcontroller, if the power management features are properly used, can use so little power that it’s not worth worrying about. Let’s use 50 mA when the LEDs are on and a round 0 mA when off as the estimate.

You estimated about 1 use every 6 hours. Let’s double that to take into account the two modes you have, so 2 minutes every 6 hours. We’re just estimating anyway, so a ballpark like that is good enough.

Now, figuring out your average battery drain over the entire operating period is just a matter of multiplying and dividing the right numbers together.

2 minutes / (6 hours) = 0.556% operating duty cycle.

50 mA * 0.556% = 0.278 mA average current usage

0.278 mA * 72 hours desired operation = 20 mAh

20 freaking milliamp-hours. That’s 1/50th the capacity of the battery in CrossRoads’s photo. This 40 mAh LiPo from Sparkfun is half the size of a quarter. Or there’s their 110 mAh E-Textiles LiPo with an addition short-circuit protection circuit built into it (so you won’t catch fire even if something accidentally gets pinched or frayed in the costume).

Definitely go with a 3.3V Pro Mini. You can run it directly off the battery that way without all the extra voltage regulation and programming garbage that’s on a normal board (even a Nano has them).

It is easily possible to meet and even exceed the requirements you have outlined, you just need to know what to do.

The key concern here will be driving the LEDs. You need to know what arrangement and types of LEDs give you the visuals you want. depending on how much current you want to put through them and what voltage they require, the may need an external regulation circuit to provide them with consistent drive as the battery discharges.

Can the LiPo battery be charged through the pro mini through the serial port attachment?

Don't worry about 3.3V or 5V Minis, every Mini can be powered from 2.8V to 5V at Vcc. The only limit is the processor clock, i.e. you should select the 8MHz 3.3V version during program upload. The lower clock frequency also reduces power consumption.