Powering a LED strip from a Pico?

[Liam120347]

Hi Steven,

I’ma answer your questions out of order so they hopefully ship information a bit faster…

@Steven

but I was wondering how the Particle Photon in the Infinity mirror kit does it.

The Infinity Mirror kit is able to use the power passthrough via the 5V pin on the photon.

It’s a little harder for standard Neopixels (WS2812B’s) to be powered by a battery since they have a much higher current draw (60mA at max brightness), the GlowBits (WS2812Bv5) boast a much lower current consumption at max brightness - though unfortunately they arent available as strips.

@Steven

Would it work? I assume the LEDs would be dimmer.

It most likely would work but at lower voltages Neopixels don’t uniformly lose brightness across each channel (RGB) .

I got a deece pic of the effect a while back (the end of the strip measured 3.8V, just above a LiPo’s nominal voltage):

12 day project: ESP32 - LED controller

Testing the voltage drop across a strip My excess of LED’s helps a bit here. I theorise there are two ways you run into this issue, both being interwoven. And can be easily cimcumvented by injecting power along the length - however if the strips come in IP rated sheaths it the waterproofing is gone I wired up 10m (600 LED’s) of strip with a couple of headers on the end, ran the strip with each LED trying to output RGB: 45,45,45. You can clearly see the change in colour on the end of…

@Liam120347

To keep things easy to source and assemble, a voltage divider will work a treat.
To find the upper bound of the ADC I refered to the MicroPython documentation (it is also on the ESP32 electrical specifications datasheet). 1V is the maximum unattenuated voltage (not a concern on most other devboards) - and I’ll stick to this as any software mishaps wont break anything.

@Steven

My requirements:

• LED strip around 1.5 - 2m long
• Want to control brightness
• LEDs don’t have to be individually addressable
• Doesn’t necessarily have to be RGB, white/warm white is ok.
• Battery powered as I’m trying to avoid running a power cable across the living room.

To throw out some figures:

• 30led/m at 2m = 60 LED’s = 60*0.06A = 3.6A - at 60mA, 20mA is more reasonable and only 1.2A - enough for a USB battery bank to power, double this for 60led/m and so on
• Brightness control will be a breeze with addressable LED’s otherwise the ‘analog’ strips are a lil bit harder to put together IMO
• Kmart, Coles and some other supermarkets stock different styles of LED strips, some with in-built USB inputs, might be worth a look in though you don’t have that customisability
• Batteries will very much depend on the type of LED’s you wanna use

I’m keen to see what you do!