Battery-powered programmable LED Strip


I've been searching tutorials, forums and electronics sites in search of help for my project but haven't progressed very far yet unfortunately! I was hoping I could get some help or pointers for my project if I described it here. Essentially I want to make a very portable (as small and lightweight as possible) programmable 60 LED strip (1 metre) powered by rechargeable batteries that must be recharged in place (not removed from device) and controlled by a microcontroller that will be programmed via USB and will take inputs from up to 3 buttons (if not a wireless/RF remote instead) and a simple accelerometer/g-sensor. To start with I just want to make a working version that has the LEDs, microcontroller and batteries/recharger - the buttons, remote and accelerometer are future projects. I will describe my current progress and ideas/problems below in the hope that someone kind can help out!

Microcontroller: As I want to control a 60 LED 1 metre strip (see here) in such a way that as well as doing simple colours it could play fast 'animations' I required a microcontroller with sufficient RAM etc.. It also has to be lightweight and very small (fit inside a kitchen paper cardboard tube comfortably) I believe the Teensy 3.0 is my best option (see here). I just need verification from someone in the know that this will be able to control 60 (or more) LEDs comfortably and it can take buttons, wireless/RF input and an accelerometer at a much later date. Or perhaps there is a more suitable controller given my size/weight restrictions? As I understand it an Arduino Micro would have very limited RAM left for the LEDs and others have used the Teensy 3.0 successfully with these WS2811/WS2812 LED strips.

Batteries: This is somewhere that I am struggling to find a solution. The LEDs require 5V but the Teensy 3.0 would require 3.3V. Furthermore, as I want the batteries to be rechargeable without removing them I'm left with having to use a lithium ion battery like this one. However that runs from 4.2 V to 3.7 V and if it is to fit inside my kitchen roll sized device with room to spare it can only be large enough to have a capacity of around 1200mAh. The LEDs would require quite a bit of power which I'm not sure these batteries could provide (3.5A at max brightness, but could run at reduced brightness), however, I only need the device to work for around 40 minutes before recharging. Lastly, I need to be able to recharge it while it can also function, for a single cell this isn't a problem - see this recharger.

Here are the problems: - A single cell wouldn't produce 5 V unless it is stepped up but then it wouldn't be able to output enough current. - Two cells would produce 7.4 V which could be stepped down to 5 V (and then 3.3 V for the Teensy 3.0 - is that possible?) but then they must be recharged as described here but this would required a 3-pole double throw switch that isn't ideal (I required a rocker switch but 3-pole rockers don't exist I think...) and means the LEDs can't be on while recharging which I require.

As you can see I'm stuck! So if anyone could help out that would be very much appreciated! Thanks :)

You can use a voltage regulator on a big battery to get a low voltage. Start out with a car battery at 13.8 volts. Use several LM317 voltage regulators to get 3.3v and all other voltages you want. When it all works correctly, get a smaller battery.

Hi. I'm just starting in the world of arduino and digital electronics so my question might be completely stupid. Won't the LED Strip work at 3.7v but simply be less bright? I'm kinda wanting to do what you describe in the OP, but I haven't got around testing it yet.

That particular LED strip is built from these chips and will run from a supply voltage as low as 3.5V. power. So a single high capacity 3.7V to 4.2V cell would power the LED strips okay. Just need a small regulator to make 3.3V for the Teensy if needed.

WS2812B.pdf (381 KB)