0
\$\begingroup\$

I was planing on using a Raspberry PI Zero W for å smart lamp project with WS2812b LEDs, to avoid separate power supply for the LEDs, my plan was to power the LEDs from +5VDC on the RPI ZW. The lamp is going to have 18 WS2812b leds, so total power consumption is going to be 1080mA(*) at full brightness.

I have read that the RPI has a fuse at 750mA @ +5VDC, so the question is, can I power opp 540mA @ +5VDC with LEDs from the RPI? I do not need USB ports or anything else than 1 I/O-port to data for WS2812b and WiFi connection.

(*) Corrected my math mistake from 540mA to 1080mA

UPDATE:

I have decided to only use 16 WS2812b LEDs and by software set it to half brightness (128,128,128) so the maximum current only is 480mA.

\$\endgroup\$
  • 1
    \$\begingroup\$ How will you be powering the raspberry? \$\endgroup\$ – Vladimir Cravero Feb 20 at 18:23
  • \$\begingroup\$ With a 1A @ +5VDC USB adapter. \$\endgroup\$ – BufferOverflow Feb 20 at 18:26
  • 3
    \$\begingroup\$ This is a bad idea regardless if it is within or (or more likely not within) specification. As a general rule, connect your load directly to the supply (or via its own overcurrent protection), so that the high load current does not pass through the embedded computer's board. \$\endgroup\$ – Chris Stratton Feb 20 at 19:39
  • 2
    \$\begingroup\$ Yes, you're right it is the same node. But if you are supplying the 5V using the USB mini connector, how much current can the mini connector itself and the PCB traces handle? (The traces from this USB to the 40 pins connector). If you would PWM the leds, the same traces could induce crosstalk/noise as well). I would recommend using the 5V on the 40 pins connector as (5V) star point. \$\endgroup\$ – Huisman Feb 20 at 20:31
  • 1
    \$\begingroup\$ Preferably run a lead from the power supply to the GPIO header's adjacent 5v and GND to supply the pi; and a separate lead from the power supply to the LED strip. If you use a buffer to drive the LED strip, that might share the strip's supply. \$\endgroup\$ – Chris Stratton Feb 20 at 21:57
2
\$\begingroup\$

Looking at the datasheets at https://www.raspberrypi.org/documentation/hardware/raspberrypi/schematics/README.md, the PiZeroW has no fuse. (Compare for example with the Pi 2B, which has a fuse at the USB input)

Now, a Ws2812b draws 60mA when set to full white brightness (255;255;255). This makes 1080mA, which is already more than what your 1A power supply can output. You may be OK if you don't set too many LEDs too bright, but still, your Pi takes up to 250-300mA on its own. Consider to get a stronger power supply.

\$\endgroup\$
  • \$\begingroup\$ By disabling eg HDMI and picking the right software you can lower the current consumption of a zero down to 80m, so 250-300mA is a bit overrated: it is only for the standard configuration. \$\endgroup\$ – Huisman Feb 20 at 20:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.