Powering the Photon using Vin

As soon as the board is powered via the USB port, the on board LED will flash red/white/blue, then flash green, then flash blue- the loaded code will now be running, and all board functions acting properly.

When powering the board directly via the Vin and ground pins (using power voltage in the 3.6V to 5.5V regulation) the on-LED will continuously flash its red/white/blue color mix, and never begin to run its loaded code or any of its operational functions. It will supply the 3V3 pin with output voltage briefly, then not at all. This seems as if it would have a trivial solution, but I have been unable to find a detailed discription on how the board should operate when powering it directly from Vin. Any advice or info would be appreciated. Thanks!

I’m not sure why it’s not working for you. It should work. I just double checked by putting 4.86 VDC between VIN and GND and the Photon booted up and ran just fine, like it normally does when powered by USB.

What sort of power supply are you using?

How well filtered is your DC?

BTW: What kind of color mix is that?

That doesn’t sound like the standard bootup procedure.

I am using a Agilent E3631A bench-top power supply, with voltage and current limits set at 4.86V and 0.1A respectively. plugged directly into the VIN and GND pins. It initially turns on with its red/white/blue color scheme, then very briefly turns off and back on again. Looking at the supply voltage/current readings, the current will spike up (with the voltage dropping down) for a brief moment, resulting in what I believe to be the board just turning on and off again, repeatedly. Thus looking like the red/white/blue color LED is “blinking.”

Juice up the current a bit - try 500mA at least (this is what USB should supply as the Photon is enumerated as a 5 unit USB device).

The WiFi will demand some current to power up and connect that will definetly exceede your 100mA.


The color you call red/white/blue is commonly just refered as white (all three RGB sub LEDs equally illuminated).

Yes, what I was referring to as red/white/blue is just the “white” led that is referenced in the data sheet. Once I increased the limit to 500 mA, and it booted up properly. Thank you for the assistance.

For future reference of anyone else who runs into a problem similar to this, here is a video of the blinking status/ supply readings: https://www.youtube.com/watch?v=aRIGYPJdscI

Sounds like the supply was current limiting which would cause brown-outs when the WiFi chipset transmitted.