thehookup/Holiday_LEDs_2.0

Power Consumption Chart Seems Wrong

kspearrin opened this issue · 4 comments

kspearrin commented

Hi,
Referencing your power consumption chart here, I am getting drastically different results.

Test

Results

Results are for the entire stripe, 150 LEDs @ 100% brightness, power injection only at the beginning

  • Single channel - 16.2 watts
  • All channels (RGB, white) - 27.3 watts

If I add power injection from both ends to compensate for the voltage drop, I see all channels consume ~40 watts.

Why are my results so different than yours? My numbers seem to be about exactly 2x yours for WS2812b.

sslupsky commented

Looking at the power meter you included the link for, it appears to me you are measuring total power including the power supply. So, the efficiency of the power supply also affects your power measurement. The believe the chart shows power consumption for the LED strip only.

sslupsky commented

@thehookup On a somewhat related note, could you please also create a chart comparing LED string power consumption? I am particularly interested in the difference between the two types of "regulated" pixels. I was reading over at doityourselfchristmas.com that there are two types of regulated pixels, linear and buck. The former uses a linear regulator which doesn't do anything to improve efficiency but helps reduce artifacts due to voltage sag. The latter uses a buck switching regulator which improves efficiency and voltage sag artifacts. I have been attempting to locate a supplier of the buck regulator style pixels to try them but so far have not had any luck finding them.

smirgol commented

I'm a little bit confused by the consumption of the WS2812B too. Everywhere I read they say that each LED consumes 0.06A at maximum brightness, where the chart says it's only 0.0182A. That is a factor of 3 and makes the difference if I can get a "regular" power supply or need one of these aluminium bare bone ones.

Also, the chart says 0.18 watts for "RGB Channels Per 1 LED", but "RGB Channels - 150 LEDs" says a total of 13.65 watts. Now, when I do the math - 0.18*150 - I get a value that's double of what the chart says: 27W versus 13.65w in the chart. What am I'm missing here?

thehookup commented

@smirgol Voltage drop is what you are missing. The traces that run through the LED strip provide significant resistance. If you are powering a single LED at the beginning of the strip it is able to pull near its maximum current (.18 watts/5v = 0.036A), but as the voltage drops moving down the strip the current draw also decreases substantially. There is a google sheets document with whole strip values corrected for voltage drop: https://docs.google.com/spreadsheets/d/1-L0YvDVq_V17lLOeBc-H19np4wcSLqI6X5i6OAOGoaM/edit#gid=0