Here’s a confusing thing: when i use the rainbow function over 144 LEDs, i get a reading of 2.93 amps. I assume that’s a 1/3rd of full brightness, meaning 144 LEDs at full brightness is just under 9 amps. Is that not the case?
I don’t know, I haven’t measured the current draw? I only have a Plasma Stick. It doesn’t have current sensing. My supply is currently soldered in place to the pigtails on the LED strip, with heat shrink added. I’d have to cut the wires to put an ammeter in.
Brightness and color are (somewhat) independent, at least the CircuitPython library can change the brightness independent of color.
I think it depends on the device (RGB LED). My Unicorn LED matrixes have a Micro Python global brightness function. My Interstate 75 doesn’t. I had to go HSV to get that kind of operation.
I’ll have to go that same route with this LED Strip. If I want to adjust it on the fly with a button or encoder. For now I just went (155, 155, 155). It’s I guess, a soft white.
ChatGPT says 144 * 60ma = 8.64 amps, which matches (more or less) my calculation. So it’s unclear how you got full white out of 5v 4a, to be honest!
I likely didn’t. It might be that this power supply limits the current to 4A, and doesn’t shut down or reset. It may be reducing the +5V to stay in spec. The Pico can run on less than 5V.
To be honest, my current full bright, is more than enough to illuminate my desktop. Right now I’m at (75, 75, 75). Dark room with no lights on.
The Official Pi 4 supply, I suspect, was actually shutting down (turning off) and restarting? Or the voltage dropped so low the Pico shut down and restarted?
Long story made short. I’m good with what I have.
Hi. Got the multimeter out and did some testing:
results for ws2812b:
using (255,0,0) I got:
1 LED: 0.48mA
144 LEDS: 1.80A
(some variation between R G and B, 1.80 is the highest amperage i got from these tests, on red)
using (255,255,255) I got:
144 full white LEDs: 3.94A
72 full white LEDs: 2.54A
36 full white LEDs: 1.37A
18 full white LEDs: 0.73A
1 full white LED: 60mA
The relationship between brightness and amperage is NOT linear. e.g.
Full red, 144 leds, (255,0,0) = 1.8A
Half red, 144 leds, (127,0,0) = 0.45A
I have a hard time wrapping my head around the number versus brightness. Changing it does affect the brightness but its more to do with what color you want versus how bright the LED is, as I understand it anyway?
(127, 0, 0) is MAROON, RED.
If you really want to make your head hurt try using HSV instead of RGB.
Make rainbows with Unicorn HAT (pimoroni.com)
I’ve gone this route to get a global brightness (of sorts) option on some hardware. One being my Plasma Stick LED string. I can now adjust how bright the LED’s are with my Encoder Wheel breakout. On the fly with it running.
And from what you posted I must have been hitting the current limit of my power supply. The Official Micro USB Pi one for sure. It tops out at 2.5 A
I’m using the term “brightness” as measured by the value sent to each LED. So full brightness is (255, 255, 255) because red green and blue are at maximum brightness. It’s true that some colours look brighter than others, but I’m not actually interested in measuring that, I just want to know if the brightness/colour is consuming more power than my supplies can give.
p.s., (127, 0,0) is red, but (255,0,0) is also red and it’s twice as “bright” according to my system. In my use case, brightness is important!
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I totally get what your saying and how it affects your setup. It gets really interesting for me as I’m partially color blind. I have what they call a red green color deficiency. I can see red and green though. Turquois as an example, either looks green or blue to me? There is no in-between for these eyes. There are a few others that are a bit off too.
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I took the subjective interpretation out of it and just counted the amps and the RGB values ☺️ but even so it was crazy to see just how non-linear it can be.
The main take home is that 255 255 255 requires way WAY more electricity than 240,240,240.
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The LED strip type (type of LED’s) likely factors into it too. Mine are the 3 pin WS2812. 144 in total on my strip.
I think (230, 230, 230) was OK with the Pi Micro USB Power Supply. It was something like that, (255, 255, 255) caused the power supply to trip and restart. The Pico just kept rebooting.
For me full bright is actually too bright and not needed. Not in white anyway. I crank the brightness up with the patterns, but its just for showing off. Most of the time my strip is lit up white to illuminate my keyboard.
Hi,
Just replying to my own post as I’m multimetering a big big 10w 12v RGB LED from aliexpress and want to store some notes on amperage.
Results are from one pixel.
Full blue: 0.29
50% blue: 0.05
Full red: 0.26
50% red: 0.04
Full green: 0.26
50% green: 0.04
Full white: 0.82
75% white: 0.41
Half white: 0.13
nice warm yellow: 0.44
[these LEDs are GRB, so the colour is (220,255,80)
I had a failure on my setup. I’m not sure if it was the Plasma or the power supply? Power supply was dead, and I replaced it. The plasma was also wonky, it would just lock up and quit working, and not recover with a reset. A power cycle would get it working again. I replaced it anyway.
So far so good, no repeat of that failure.
interesting. When my code stopped working it was often because I was trying to set an LED which was higher than the limit set at the beginning of my code. i.e. led_strip.set_rgb(741,0,0,255) when you only have specified 740 LEDs. That caused a crash with no error message.
I have to say, however, that the Plasma library is absolutely fantastic otherwise. Very simple, very fast, and very error-free.
Same exact code on the new one works OK. I also reflashed the glitching one, but it still just quit working. Wouldn’t show up in Thonny either, until you power cycled it. I got worried it was what blew the power supply so I took it out of service for good.
Strange… if it potentially damaged your power supply, take it out of circulation and forget about it.
I realised you can install the plasma library on a normal pico and it works fine (if you don’t need USBC), so I don’t buy plasmas anymore (I had probably 5 and they all worked fine though. Neat little board.)
I’ve been buying the Plasma Stick (Pico W onboard). I have plans some time down the road to make use of the WIFI to control what pattern gets used. And the Level Shifting and screw terminals come in handy.
I got that working, though it was very shaky, made version that worked via Bluetooth and WiFi. I actually ended up using a picoW to receive signals that were sent on to a Pico that was connected to the lights. I think I did this because the WiFi or Bluetooth blocked the thread so you the lights would pause.