Battery Options to Power Arduino and NeoPixel LEDs

[samirparikh]

Hi Everyone,

This is a follow up question to the "Making Police Lights for Bicycle" question I posted a few weeks ago.

I've decided to use 24 NeoPixel RGB LEDs and either an Arduino Nano or a 5 volt Pro Mini (which does not have USB). Assuming a worst case draw of 60mA per LED, I'd need a plan for 1.44A of current.

What is the best battery option to power both the Arduino and the LEDs?

I think have a few options:

(1) Take 4 x AA alkaline batteries and configure them in serial to supply 6 volts. Place a 1N4001 diode inline with the batteries to provide a 0.7 volt drop as described here. I could then power the Arduino via the 5V and GND pins and also power the NeoPixels with their VCC and GND pins directly from the batteries. However, I've heard of risks of providing an Arduino power directly through the 5V pin. And I may be pushing the limits of the diode with my current draw.

(2) Use a 9 volt battery to power the Arduino via the VIN pin (Nano) or RAW pin (Pro Mini) and use the onboard voltage regulator. I'd also have to connect the battery to some type of linear voltage regulator or voltage converter (buck converter) to provide 5 volts to the LEDs, as suggested in this post. From what I've read however, a 9 volt battery may not last as long but personally, I don't mind and appreciate the smaller form factor. I've just never used a voltage regulator or converter before.

(3) If I go with the Arduino Nano, I can try to power it via a USB power bank. Does anyone have suggestions for a suitable battery? And how would I get power to the LEDs? I don't think I'd want to use the 5V pin on the Arduino to power the LEDs due to the current draw.

(4) Similar to the first option, perhaps use 3 x AA alkaline or 4 x AA NiMH batteries to power both the Arduino (via the 5V pin) and the NeoPixles (via their VCC pin).

My preference is for the simplest option but don't know what is best. Any suggestions would be appreciated.

Thanks!
Samir

[Koepel]

A few notes:

First of all, could you limit the maximum power ?
Try to set the overall brightness to about 25% (64) or even lower. Is that so bad ?

I suggest to use the Nano. In the past, when I wanted to update a sketch of a Pro Mini, then I could not find that usb-serial module anywhere.

I think it is better not trying to match the voltage. Use a DC/DC-converter, also called step-up or step-down (or a module that can do both) as suggested in the other topic. Then you can use a 12V battery or a 3.7V battery or any battery. You may apply the 5V output of a DC/DC-converter to the 5V pin of the Arduino Nano.
Using 4 NiMH batteries with a diode is a quick and dirty fix. It is okay I guess.

A small 9V battery might last a few minutes. It can not provide current.

A power bank is a good idea. You may power the Nano via the USB connector, but also directly to its 5V pin. If you have a strong 5V and a thick wire and touch the 5V pin, then the voltage regulator on the Nano board might get damaged by the current peak. If you can avoid that, then it should work.
A custom USB cable to give 5V to the leds and to the 5V pin of the Nano should be okay.

[gilshultz]

You have part of it, 1.44A, however the Arduino also needs power, so round it up to 2A. Then add the current consumed by your voltage conversion method. That now becomes 2 amp hours +. Now how long is this to operate, multiply the two to get the total amp hours needed. Is this going to be operated daily or whatever. Next check your budget, using primary cells is expensive, rechargeable although they cost more are much more economical in the long run. With this information you can make a good decision.