Power usage/demand

Hi, I’m wondering if there’s a way for the allpixel to report actual power usage and demand.
I’m running 600 which theoretically requires 36A, so finding out how much my application uses and being able to give it enough but not have to add un-necessary overhead would help.

@Tallis161 - Are you asking if the AllPixel could report actual power usage or that BiblioPixel could report an estimated power usage?

Actual power usage is not possible with the hardware available. Though you could place a multi-meter in-line with the power input to your AllPixel to measure the usage. Or if you have a bench power supply or similar you could power the AllPixel from that and use it to monitor the power draw.

BiblioPixel used to actually have the option to output the estimated power draw but it was removed because it seriously slowed things down. Basically what it would do is this:

def get_current():
    current = 0
    for r, g, b in leds:
        current += ( ((r/255) * 20) + ((g/255) * 20) + ((b/255) * 20))
    return (current / 1000)

The above would return a float value of estimated current draw in amps, based on the assumption that each channel of an RGB LED draws 20mA. Which, for another reason I removed it, is not always true. It depends on your LEDs.

However, you can estimate max theoretical usage with the following calculation:

current = (numLEDs * 0.06) * brightness

Where current will be in amps and brightness is a value from 0.0 to 1.0.

This will give you the max current draw if all LEDs are full white.

To wrap up though… let me just say this: You really shouldn’t run 600 LEDs only through the power input on the AllPixel. With that many LEDs you really need to wire in power manually and ideally from both ends of the strip. Basically, just connect ground, data and clock (if you have a clock line on your LEDs) but do not connect the power line to the AllPixel. Then connect the power for the LEDs to a separate power supply and run another wire from ground on the power supply to ground on the AllPixel output header. DO NOT skip the ground step! It won’t work if you don’t do it.

Using the above method I’ve run very large displays. Do not go above 15 amps from one end of an LED strip. If more than that, connect power to both ends.
If more than that is required you will need to “inject” power at multiple points in the strip, possibly using more than one power supply. If you use more than one supply, just remember to always connect the ground lines together but NEVER connect the power lines of multiple supplies together.

Hope that helps :slight_smile: