February-28th-2019, 12:35 PM
(This post was last modified: March-9th-2019, 04:09 PM by Armin@netPI.)
LED sticks like these here https://www.blinkstick.com/ are nice gimics to extend netPI by further lights.
One major concern is the inrush current that arises when the LEDs are switched on. With blinkstick LEDs their triple color LEDs for example are directly connected to USB +5V without any resistor and hence take full effect on the USB host's (netPI) +5V power supply. The inrush current may vary from 1 to 80amps if you follow forums and user stories on the internet if you search for terms like "inrush current high power LEDs". Nobody can really tell you the exact current draw in the event you switch them on except you measure it by yourself.
netPI's 4x USB ports are limited to deliver 1000mA of current over all 4 ports in maximum. Higher values are out of specification and could lead to USB drop outs in terms of communication inpendent if it the current draw is static or pulsed for even some µsecs. Linux for example would report the loss of USB connection similar to somebody unplugging the USB device and reconnecting it.
In netPI operates a step-down regulator XR76205 that turns the 24V input voltage to 5V USB. It has a fast load transient response when the output USB load changes. It is good to react on cases where a new USB device is plugged in and he regulates the voltage back to 5V after the first current impulse to keep the voltage in all cases higher than 4.75V. But for LEDs (and multiple of them at a time) with unpredictable inrush current during their switch on phase this guarantee for a proper operation cannot be given.
So please avoid using the LED sticks and stripes especially if you are operating additional USB devices the same time needing a 24h proper USB connection.
One major concern is the inrush current that arises when the LEDs are switched on. With blinkstick LEDs their triple color LEDs for example are directly connected to USB +5V without any resistor and hence take full effect on the USB host's (netPI) +5V power supply. The inrush current may vary from 1 to 80amps if you follow forums and user stories on the internet if you search for terms like "inrush current high power LEDs". Nobody can really tell you the exact current draw in the event you switch them on except you measure it by yourself.
netPI's 4x USB ports are limited to deliver 1000mA of current over all 4 ports in maximum. Higher values are out of specification and could lead to USB drop outs in terms of communication inpendent if it the current draw is static or pulsed for even some µsecs. Linux for example would report the loss of USB connection similar to somebody unplugging the USB device and reconnecting it.
In netPI operates a step-down regulator XR76205 that turns the 24V input voltage to 5V USB. It has a fast load transient response when the output USB load changes. It is good to react on cases where a new USB device is plugged in and he regulates the voltage back to 5V after the first current impulse to keep the voltage in all cases higher than 4.75V. But for LEDs (and multiple of them at a time) with unpredictable inrush current during their switch on phase this guarantee for a proper operation cannot be given.
So please avoid using the LED sticks and stripes especially if you are operating additional USB devices the same time needing a 24h proper USB connection.
„You never fail until you stop trying.“, Albert Einstein (1879 - 1955)
