Help With Expected Current Draw

[ukkeef]

Hi,

I wonder if anyone can help? Xlights Expected Current Draw on the Visualiser page seems to assume 5 volt pixels. Can that be configured?

Thanks,

Keith

[allknowing2012]

Not an electrics guy but is the amperage the same on 5v and 12v - xlights is coded to use AMPS_PER_PIXEL 0.055. Cannot be changed and is used along with light count and brightness.

[AAH]

Not an electrics guy but is the amperage the same on 5v and 12v - xlights is coded to use AMPS_PER_PIXEL 0.055. Cannot be changed and is used along with light count and brightness.

Sadly the current isn't the same. 5V pixels are current limited to 18.5mA per colour and remain constant kind of regardless of voltage drop until the volts drop down to about 3V. 12V "resistor" pixels have a resistor in series with each of the 3 leds and the WS2811 IC cannot current limit the leds to 18.5mA before the PWM control begins. At 12V in the first leds will have something like 8.5mA per colour. Further down the string (assuming lights are on) the voltage could be down to 9V and the current for each could be 4mA per colour. At the extreme the pixels will work down to below 5V where the current per colour could be down to 1mA per colour. So a 5V pixel will relatively constantly be 55mA per pixel at 100% white. A 12V resistor pixel can be anywhere from 25mA per pixel down to 3mA per pixel.
12V seed pixels and gumdrop pixels are more like 15mA per pixel.

The easy and relatively safe way to calculate for 12V resistor pixels is to halve the 5V pixel current scaled by the brightness setting. 50% is going to be the absolute highest that it's going to be. A string of 50 might be close to 12V (25mA) for the entire string but a string of 750 on a big prob is probably going to work out to under 30% of the 5V current.

[ukkeef]

Thanks for the replies. allknowing2012 has answered my question. I only have 12 volt pixels connected and the expected current draw based upon the number of pixels I have connected seems to be based upon 5 volts. I didn't know if it might be something to do with me using a falcon f16v3 as i know there is a bug in 2.59 firmware that causes it to display the voltage incorrectly. THanks anyway

Keith

[allknowing2012]

The voltage display on the falcon v3 web page is suspect - always was - something about it being done via software and not a true voltage reading. It is supposed to show the input voltage  - dont trust it. Use a meter.

[jnealand]

In 20 years of doing animated lighting I do not recall ever looking at detail electical numbers and such.  I never push any port on any controller to the commonly quoted max counts that I read in the forums (In general for me that means 300 per port at 30% brightness).  I seldom use every port on my controllers in order to have few backup ports available in case I need them and in those 20 years I have on occasion needed them.  Seeds and EVO and other newer tech lights are changing those old numbers but I still see no need to look at detailed electronic numbers.  There is nothing like hooking up actual lights and controllers in your workshop and seeing how many you can connect until you start getting dimming or color changes.  YMMV