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gkaindl / ambi-tv

a flexible ambilight clone for embedded linux
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Powering LED strip #9

Closed Mrjohns42 closed 10 years ago

Mrjohns42 commented 10 years ago

Your documentation suggests that we power the LED strip from extra leads soldered into the power supply cable directly in parallel to the USB power for the Pi.

Is there a specific reason you chose to do it this way? If I recall correctly, the 5V GPIO pins are connected to the USB power. You could reduce the mess of cutting and splicing a USB cable, if you just plug the unmodified cable into the Pi and power the LED strip from the GPIO. This would have the added benefit of using the voltage regulation circuitry in the USB port to prevent potential overvoltage damage to the LED strip.

gkaindl commented 10 years ago

The thing is that in my configuration (about 100 LEDs), the strip can draw up to (a bit less) than 3A, which (I think!) is more than the voltage regulation circuit on the RPi is rated for. Also, even if it is within limits, it will unnecessarily raise the temperature of the RPi board.

Additionally, the danger of damaging the LED strip is minuscule, since you need to be using a 5V regulated wall wart anyway, and if that fails and (for whatever reason) carries a voltage much higher than that, it will fry both the LED strip and the RPi anyway.

The reason for my split-wiring is thus to spare the RPi from having an unnecessarily high current run over its 5V line.

sn00zerman commented 10 years ago

Indeed, NEVER run that much power trough your RPI. The PCB traces are not design for that much current. Also, the voltage regulation will blow out definitely !