Running servo from photon


#1

Okay so I was using the servo example from the photon documentation to test out a servo and after a few successful activations of the servo, my photon no longer turns on. I hooked it up like the diagrams I found online, 5v to VIN, ground to ground and the activation wire was hooked up to D0. From what I understood the PWM signal was very low current so there was no other precautions required to run a servo. So now I plug my photon in and get no lights, not even d7 comes on dimly.

First, do I have a fired photon? I assume so I get nothing out of it, lights, pc connection. It seems like the device does heat up slightly when plugged in though…

Second, did running the servo fry my photon? I did not think the PWM required much current at all.

Thanks for any help


#2

The PWM pin is not the only one you need to consider.
Depending on the type of servo you may strain the Vin pin too.
For one the servo may draw too much power to drive the motion (also depending on the mechanical load) and the noise produced on the Vin pin may also hurt the 3.3V regulator.


#3

Okay so would you recommend an external supply to power the servo? It was also a continuous motion servo I’m not sure if that matters.

This is how I had it hooked up and this was right from the particle tutorials for the maker kit. How would you reccomend to hook that up?


#4

Yes.
But first it would be good to have a closer look at the specs for the servo you use - especially the max current rating.
You can supply the power to the Photon via the Vin pin too, so when powering the servo externally your supply should be capable of delivering 500mA more than the max current of the servo.
You may also want to add some filtering and buffer caps between Vin and GND.

If you only want to power the servo externally and the Photon should still be powered via USB make sure to connect all GND rails together.


#5

So I could in theory, cut the end off a micro usb and isolate power and ground using a 2 amp usb adapter and run the photon and the servo? The servo advertised a stall current of around 500ma.


#6

That should work.


#7

@natebc22 -

My two cents worth… I never power motors from a Photon (or any MC for that matter). I always use external PSU. I have note used Servo’s though, always been using Steppers of all shapes and sizes. Without fail, I run them through a dedicated driver with External PSU.

As @ScruffR mention, don’t forget common ground in such cases :slight_smile:

Good luck.
ps: Photon slightly heating up does not necessarily mean a problem, I fried one before, they get hot as hell in such a case. No lights sound bad though, have you tried Particle Doctor? Is it picking up the photon?