Fun with RGB LED Strips - Part 8: Driving a Full Reel

Today I got a full 5 m reel of the SMD5050 LED strips I'd been playing with, so I decided to try it out. Unfortunately, I can't really drive it at full intensity, since the power supply I ordered hasn't come yet. Each full 5 m strip (64 LEDs / m) supposedly draws a maximum of 19.2 A or 96 W (all RGB channels at max), though it's not yet clear to me that that number is correct. So I've got a 40 A 5 VDC supply coming, which will be adequate for driving two full strips.

The theoretical maximum current number is based on the SMD5050 per-LED max current of 20 mA:

20 mA/channel × 3 channels/LED × 64 LEDs/m × 5 m = 19.2 A

I'm suspicious of the actual power consumption because I was able to drive my 1 m strip white without a noticeable drop in brightness, but my current power supply delivers only 1.5 A. I'll throw a meter inline with power when I get a chance to see what's actually going on.

At any rate, even at a reduced brightness level, it looks pretty. :-)

Here's a 'scope picture showing the SPI data activity:

At an 800 KHz bit pattern rate (effective bit rate for the WS2811, not the SPI bit rate which is 4x faster), each single data transmission for one 5 m strip takes 9.6 ms:

(1 / 800 KHz) s/bit × 8 bits/channel × 3 channels/LED × 64 LEDs/m × 5 m = 9.6 ms

That means I can run things at an update rate of 60 Hz with no issue whatsoever.