Powering a LED strip from a Pico?

[Steven]

Is it possible to power to a LED strip from something like a Pimoroni Pico LiPo (or similar), with the microcontroller itself powered by a LiPo battery? From what I gather, most strips require 5V for power, and some even want 5V for the data pin.

I know this has been asked a few times here, with the answer usually “no”, or “probably no” but I was wondering how the Particle Photon in the Infinity mirror kit does it.

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

I’m thinking of doing an infinity mirror coffee table build myself.

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.

Thanks for your help everyone!

[tepalia02203352]

It depends on how much current your particular LED strip draws.

[Craig207079]

The electronics side is pretty easy , id struggle building one to put the leds in lol

[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!

[Steven]

Thanks @Liam120347 for your super-detailed reply and suggestions! In the end I went with ready-made LED strips. I ended up building two(!) coffee tables as by sheer stoke of luck this project came way under-budget.

I found two second hand coffee tables on Gumtree @ $35 for both. The glass on the top was already tinted, so I didn’t need to buy any mirror film.

IKEA just happened to stock the EXACT size mirrors I needed @ $10 /ea.

Zigbee RGBCW led strips, $25/ea. They take 5V USB-A input, and I plan to power one or both from a USB battery pack. I’ll be interested to see how long it lasts between charges.

Photo doesn’t come close to doing it justice but you get the idea. And yes the glass needs a good wipe down.

I wasn’t sure whether to get cool or warm white, but I think the cool really “pops”.

So ultimately not the level of fine control you’d get by programming a microcontroller with individually addressable LEDS, but it’s still pretty neat.

I do have a Zigbee dongle attached to my Raspberry Pi “server”, so I can control the LEDS via MQTT. Like @Michael 's idea in the Mirror Kit video, I could make them “smart” and glow/change colours on certain events.

I also plan to use a Piicodev ambient light sensor on a Pi nearby to automatically adjust the brightness.

Now I just have to figure out some way my housemate can control them. I was thinking of a Pi Pico W, and Piicodev Accelerometer to detect taps to toggle them on/off but since I plan to use them as actual coffee tables, I’m sure I’d get false positives whenever I put my cup of tea down.

[Liam120347]

Looks Shmich Steven!!
I cant wait to see how you throw some sensors into the mix - the knock on and off is a sick idea
Capacitive touch sensors have been my goto- at the moment