PSU Voltage Gradually Increases on Power ON

Hi Particles,

I purchased a AC/DC switching power supply like this to power a Photon. When I turn the AC on the DC voltage read by the multimeter is not instantaneously 12 vdc but quickly increases from 0 vdc. Does anyone know if this is normal for power supplies? And would this be harmful to the Photon to momentarily supply it with less than 7-15 vdc (I have the photon on the shield shield) ?

I’ve separated the circuits for now with a switch so I can wait until the PSU is reading 12 vdc before powering on the Photon.

@casche, the PSU might have a soft-start feature to prevent overshoot and “shock” on initial power-up. What I am not sure about is how are you powering the Photon with a 12VDC supply?

Hey @peekay123,

Thanks for the reply :thumbsup:

From the 12vdc psu into the shield shield’s vin/gnd :smile: According to the data sheet anywhere between 7-15vdc is fine.

I emailed particle support:


Thanks for reaching out. Let me make sure I understand your situation:

You are using a power supply with an output that gradually drains from 12 VDC to 0 VDC over a non-trivial amount of time (~1 second). You are worried that an under-voltage condition might damage the Photon.

If this is correct you need not worry. While sustained under-voltage conditions can potentially damage a Photon 1 second is not considered sustained.

Let me know if you have any other questions.

Harrison @ Particle

So it’s all good! :dancers:

@casche, as long as the voltage is RISING on power up, the shield/shield regulator and the Photon will not have any problems with your PSU. :grinning: