So far I have only couple photons with failed voltage regulators. For unknown reason when plugged into certain PC’s voltage regulator fails. Starts overheating and eventually Photon board becomes unresponsive.
I tried looking for voltage regulator online and found that I can get RT8008 but not with preset Vout at 3.3V (RT8008-33GB)
Hardware developers, can someone explain under what conditions can voltage regulator fail while connected to PC USB port? Lets assume following scenario, Photon is connected to a load of 500mA and powered by USB port which providing 500mA as well. Will undervolted lets say 5.2V instead of 5.5V damage the voltage regulator?
My project was working perfectly for half a year connected to various wall chargers, battery packs, desktops, laptops and yet as soon as I connected it to one specific desktop voltage regulator started overheating and Photon became unstable. Second Photon with the same setup connected to the same PC went up in smoke.
I was going to bring my project to market, however, now, first I need to figure out what is causing such fatal hardware failure.
I don’t know where you’re located, but you can get 5 here quite cheaply:
A 500mA load is pushing the regulator quite hard to begin with as it’s rated for 600mA max, and you have to take into account powering up the wifi section of the Photon in addition. Most regulators will ‘fold back’ and self protect when subjected to excessive load. In this circumstance the regulator output will fall and it’s entirely reasonable that this could cause the photon to become unresponsive in the short term at least.
It’s possible that this desktop’s +5v rail isn’t very accurate… if it has risen due to a fault in the PSU it might explain what you’re seeing. I’d suggest checking the 5v rail on the PC’s usb socket (the outer two pins) with an accurate multimeter for a starter.
Under volting will not cause overheating. It may cause unwanted resets (brownouts) however.
Another reason that has causec these regulators to die was noise/ripple on the supply which caused it to oszillate which eventually kilked it.
The same can happen in case of under-voltage, but that’d be more round about 3.5V and not 5V.
BTW: Double posting is not encouraged!
Thank you for suggestions.
I need to clarify that main 450mA load is connected to VIN pin which should not affect 3.3V rail. Plus VIN out is rated for up to 1A loads.
Remaining 50mA current draw is distributed more or less evenly across 4 digital pins. Theoretically there should be no reason for such failure.
But if you power off a USB 2.0 port you are only granted 500mA but the Photon will require more than only 50mA at times especially during WiFi action with poor reception.
But since some USB ports are stricter than others and there is some degree of freedom how the port deals with devices that draw more current than they are entitled to, you might well run into a situation as described above.
It sure does, since the 3.3V rail and Vin are supplied by the same USB port and if Vin draws so much current that the dynamic demand of the 3.3V rail can’t be sattisfied you’ll put some strain on the regulator.
Thank you for pointing it out. However, typically devices connected to USB 2.0 do not suffer a fatal failure because of insufficient current. Usually maximum what happens is instability of attached device not smoke.
Particle should address this hardware issue in future Photon iterations and warn users of existing problem.
Maybe it’s also an issue with the behaviour of the USB port, which might not quite behave as it should (or used to when new).
But still a point to keep in mind for a revision of Particle devices.