I have a Yukon driving the 59 Neopixels (COM3201) - and that is drawing 0.95Amp @ 5v when I drive it with my power bench supply through the XT30 connector.
Can anyone explain why I can’t my use my 5v - 3A USB-C power supply to drive the strip?
Thank you -
John
How have you got the 5V 3A supply connected, and exactly which supply is it?
I would have expected those LEDs to draw more current, in theory they should pull up to 3.6A. Did you have them all on full white when you read the 0.95 A?
Thank you for your reply. I read somewhere that a single LED can draw up to 0.24W. That would mean with all 60 LEDs on full white with 5v supply - a current draw of 60*0.24/5 = 2.88 amps. I ran the Yukon single_strip demo - with just 4 LEDs and the library error indicated I needed to supply power via the XT connector.
Just to add - the demo code is strobing red/blue - so perhaps only one of the 3 (RGB) Leds is ‘on’ a good portion of the time. So, 0.95A does not seem unreasonable to me.
Ah, I think I follow now. Yukon seems to be built on the assumption that it is the central hub for controlling your project. I think the library is assuming that you’re using an LED Strip Module to drive your LEDs. It is trying to give them power via that module, and if it can’t detect power on the power bus, it assumes something isn’t hooked up properly. Is there a particular reason you’re trying to control the LEDs with Yukon if you’re not powering them through Yukon?
The current consumption of Neopixels is a bit vague. Officially they consume about 0.06A each when at full white, x60 = 3.6A, but in practice they don’t seem to be quite so hungry. 2.88A seems a reasonable enough assumption for the maximum draw. The chips in the Neopixels themselves draw power even when the LEDs aren’t on, so perhaps that’s why four LEDs at red/blue were pulling 0.95A.
Thanks again for your reply! The Yukon has an XT connector and a USB-C connector. I just assumed it could be powered through either (with a suitable power supply/battery). I’ve run a similar demo (single_strip.py) on a Pico W and the USB PSU in question and it works fine. Perhaps I was hoping for too much. Ah yes - the PSU is the official Raspberry Pi 5 PSU. It can provide 5A @5.1v!
Feeding Yukon from USB is not the intended way. USB only powers the 3.3V rail (Pico and logic). I spent some time creating this overview from the schematics:
Yes, I think power for the modules can only go through the XT connector. The product page says:
Powering Yukon ⚡
Supplying external power to Yukon is easy thanks to its chunky XT30 connector
And doesn’t mention the USB C. I assume this is to isolate things from the high-power connection which can’t handle it.
Thank you so much to Shoe and Kurt for their comments. I’ve recently watched ‘The Pi Cast’ https://www.youtube.com/watch?v=3He4eRyJR80 where the Yukon Project engineer talks about the power supply. To quote Chris (the engineer) - USB-C does not provide high power which is ‘stupid enough’. As you both stated the USB-C can not be used to drive the modules. Hence the error/warning issued by the libraries that deal with module registration.
Incidentally - I’m trying to build a WiFi/BLE module for the Yukon using the XIAO SEED ESP32 boards blown with ESP-AT firmware.
Thanks again!
