Hi everyone! I’ve been lurking for a while and trying to learn before I really get into a project I’m working on. I’m making a festival jacket with about 500-700 LEDs (hopefully), but I’ve started stressing about the power requirements. I’ve read through a few posts here, as well as the power guide on the Adafruit website, and I was thinking I was doing alright… and then I asked ChatGPT to help me work through some things.
I realize asking AI is also asking for some degree of trouble in many instances, so I suppose I wasn’t really surprised when it suggested adding things like a level shifter (for the data line) and capacitors (at the power points) to the project. When I read the rationales, it made perfect sense why I would want to add those components to such a large project.
My question for y’all is “I don’t recall seeing anyone mention them before, so do I really need these things?” For context on me, I’ve never worked with electronics at all, so this is all new to me. My brother (who is an electronics whiz) will be helping me with some of the soldering and stuff, but I’m trying to do this project as independently as possible. I think I can manage the project without all these extras, but this potential added complexity is really giving me pause. @ZacharyRD and @zranger1 in particular, I would love your input.
You shouldn’t need any of that. 1 pixelblaze (either with an output expander and 8 100-pixel runs, or with power injection along a continuous run), a power source, and LED strips.
800 LSDs might be a lot for a wearable for power draw (I have a scarf with 300 that will go through two 5000mah battery packs in a night), but you can get 20Ah battery packs, so you should be good (or go with seed pixels that are less bright, but 1/3 the power draw, and less prone to breaking in a coat than strips).
PB already takes care of the level shifting for you on the data line, so if you are using PB you can safely ignore that. (For info - the AI info is correct if you are using a bare MCU (Arduino Teensy etc) to roll your own controller).
Capacitors on the power lines is a slightly trickier one as it depends on your led choice, power supply and patterns you want to run. Best way to think of capacitors is that they are like a mini pressure balloon of electrical charge that can react very quickly. I.e. imagine going from all LEDs off to all LEDs on full white the change in power requirement is a massive jump. Capacitors would provide this power faster than you can blink your eye giving your power supply chance to catch up. Hopefully makes sense?
You’re very unlikely to do any damage if you try without extra capacitors as your power supply (and some LED strips) will already have capacitors inside and these may be sufficient. Without getting too technical - the closer to the power use (led) the better, hence why the power supply ones might not be able to keep the voltage up quickly enough. (They also might not be big enough).
My advice would be get your LEDs and a PB and get stuck in playing with patterns, if you start seeing odd behaviours especially with dynamic patterns you might need to think about power line dips and therefor adding capacitors.
Since I was tagged I’ll basically just say skipping the level shifter is one of the many advantages of using a PixelBlaze over other systems, and if you follow the directions that I wrote in my tutorial for how to do power over USB, you probably don’t need a capacitor either although one technically doesn’t hurt anything.
Like other people have said, 800 LEDs is probably more ambitious than you want to be for your first project for a wearable, however; it means you probably can’t get away with USB-A power delivery, And overall power requirements are going to start getting problematically difficult.
One thing to keep in mind is that many LEDs only flex so much/so many times before the lines break, so keep that in mind in how you secure them and limit flex. See details here:
I ended up using water cooler tubing for my LED strips to limit the amount of flex, they see.
I probably should have added that I’m using these LEDs (WS2812B from Aliexpress). They’re going to be sewn in, so hopefully no issues with torqueing/bending them in a weird direction. My intent is to use two of these USB battery packs. They’re 40,000 mAh, and supposedly can support 5V/4.5A on the USB A ports, so I’m hoping that’ll give me enough juice. Half+PB will be on one bank and half on the other. That’s subject to change obviously, but I’m going to clamp down the brightness to 35-40% in the hopes that will allow me to use them without difficulty.
I’m going to start playing with final layout next week, I’ll have a better idea of how many LEDs I’m going to actually end up with then. It’s for a rave/circuit party, so I’m obviously wanting to stand out and get some attention, but I’m not opposed to it having fewer lights for the sake of simplicity. It would be near identical to the jacket ZacharyRD made in the linked post above, except I’m taller so more length/lights.
One thing to think about… you will likely get sweaty at the rave and you need to think about the moisture. Make sure to heat shrink or “pot” your joints somehow.
ZacharyRD mentions it in his guide, but I think it should be mentioned again; Using a USB Power Meter (something like this) makes estimating and calculating power needs a breeze.
You can also measure the real capacity of your powerbanks since they are A) Almost always overstating their capacity, and B) the mAh are usually at 3.7V meaning the mAh at 5V is lower.
Charge your power bank to 100%, plug your strip/controller in and take note of the time.
Check the USB Power Meter once ~1hr and take note of the % on the power bank (if it has one), how many mAh has been used and the time.
Repeat this and you can estimate the powerbank’s capacity and how long it can power your preferred patterns
Also check the W being used for the brightness and patterns you’ll be using.
Cheers
Edit: Here’s what my underwhelming power test notes look like:
I was in similar boat as you are a few months ago. In the end using single 10000mAh powerbank, no additional power injections etc. The jacket has close to 600 leds.
