Powering via USB-C

[drbroom]

Hi there,

I’m entirely new to this scene and am interested in using the Pixelblaze V3. I have purchased 2m of addressable RGBIC COB strip (https://www.aliexpress.com/item/1005004792048106.html). This is a 5V strip and the specs list it at 6w per metre. Due to the low power requirements I am hoping to run this off of a USB-C PD power brick (Apple 30w base is 5V/3A). I also plan to only run it at low power (20-50%). The micro-usb connector can handle only 1.8amps so I will need to wire directly into LED strip and backfeed the 5V to the Pixelblaze.

I had some outstanding questions:

• Will 15w of power be enough to run this strip at low brightness?
• Will it be safe to run this off of a USB-C PD charger?
• With no negotiation taking place with the charger, will the power output default to 5V/3A or should I purchase a decoy board and set it to 5V (https://www.aliexpress.com/item/1005004324778777.html?spm=a2g0o.productlist.0.0.571047a6dWbl2m&algo_pvid=bcab2729-ff45-4b24-97d5-7677b6e123d4&aem_p4p_detail=202211022024281350377071859530010395031&algo_exp_id=bcab2729-ff45-4b24-97d5-7677b6e123d4-3&pdp_ext_f={"sku_id"%3A"12000028760629535"}&pdp_npi=2%40dis!AUD!4.23!4.23!!!!!%4021031a5516674458684984346ea9b3!12000028760629535!sea&curPageLogUid=SNNL2yN6DP3H&ad_pvid=202211022024281350377071859530010395031_4)

Thanks for your help!

[wizard]

Many USB PD ports will not give out 3A without the power negotiation. Some may not care, and may happily output 3A, but the spec compliant ones won’t. This can be as simple as a pair of 5.1k pulldown resistors, one each on the cc1, cc2 lines for passive negotiation for 5V/3A. You can find USB C breakouts with these resistors already like this one from SparkFun.

Theres some danger if you accidentally set it for 9 or 20V with a fully negotiated USB PD board, which could cook the LEDs / PB.

@drbroom

• Will 15w of power be enough to run this strip at low brightness?

Presumably, yes, if those strips are 6W / 1.2A per meter, 2 meters will run off of 3A. You can also dial down the brightness a bit. You might need to disconnect the LEDs to allow PB to power up properly to get it to do that if it’s booting to a bright pattern and overloading things.