My latest unhappy discovery - my 12V 2801 pixels draw over 5 ma each when off. Apparently they use a zener shunt regulator. That means the SLA battery powered string of a 100 I was planning to use at a campout next week draws half an amp even when off, and with no signals going out to them, ie: when battery voltage drops below 10.5v I send all dark and then stop calling LEDS.show() - and the battery keeps draining and the voltage dropping, since by then the battery is in the steeper decline region so even half an amp drops it to 8 volts after a few more hours. (Nominal 12 Ah SLA).
I mention this because it may be an unexpeted factor for other pixel library users; I wish I had known about it before switching to 2801s.
So, among the characteristics that a comprehensive page on pixel chips and strips/strings should describe, is the quiescent current - which along with PWM rate is generally not advertised and must be dug out or measured.
I’ve ordered some relays to cut power to the string when then battery voltage cutoff triggers. At first I was going to get latching relays, but then I realized that the current cost of keeping the relay activated while the string was on is not so important, so a conventional relay should be fine.
Aside - a current of half an amp is awkward for me to measure accurately with tools in hand - it’s above the 400 ma range of my multimeters, and the 10/20A ranges don’t have much resolution. I’m thinking to get some hall effect current sensors, and integrating those in some displays, even if only during development. It would be one way to self test whether all the LEDs are apparently working, or even count the length of a string. (Tho in this case, lighting a pixel full on only adds 30 ma to the 0.54A off current).