I've read that I should use an external power supply, and not power a micro servo directly from a board, but the nano every says it can supply 950 mA out of the 5 volt pin? Would that be enough for a micro servo such as this: Sub-micro Servo - SG51R : ID 2201 : Adafruit Industries, Unique & fun DIY electronics and kits? I don't want the nano every to get damaged, overheat, etc. from powering the servo, but I'd also like to keep this circuit as simple and compact as possible. Thanks!
Also, when I turn on my nano every, it gets warm to the touch (not super super hot). Is this normal? I'm powering it with a 9V battery.
Unfortunately the Adafruit site does not mention the stall current of this servo. Reading around their Forum, someone from support said it would be reasonable to estimate something around 500mA. So it may work for some tests, but for a final design it's strongly recommended that you use an external power supply.
With something connected or alone? Some overheating might be expected if you overload the onboard regulator (which is the case bringing 9V to 5V with a 500mA load)
Keep this battery in your smoke alarm, they can't provide much current and will be drawn in a couple of hours. Start working with 6xAAs or 2x18650.
A 9V PP3 battery will not power your servo, not even indirectly through the onboard regulator.
Problems with servos powered from the Nano Every supply will be of two sorts - when starting a move/struggling against resistance, the current demands of the servo will skyrocket and likely starve the Every, causing it to reset. Secondly, the power demand will be such that the Nano will possibly overheat, and either shut down or fail catastrophically.
Best to
power the Every from a better power source,
power the servo separately, and
connect the grounds of the two power sources.
Sorry, but that's the reality.
The stall current will be in the neighbourhood of 1A. I would definitely not use the NANO 5V pin to power a servo. It doesn't change your packaging, you can use (not the best solution though) the 7.4V 18650 battery pack to supply the servos and the NANO.
Defer final battery arrangement until you have measured real-world power measurements. You may find a single 18650 with a step up can power the NANO and a 2S 7.4V battery for the servo will work.
Datasheets of discrete transistors often describe the properties of the reverse diode (aka body diode). I've read quite a few of them for selection purposes, noticing that the stated max current for this diode is either equal to the forward current or considerably lower. Sometimes, in the device description, the manufacturers explicitly mention adding a diode to the device, so I guess it makes a selling point.
The manufacturer of a DC/DC converter might consider adding a diode for protection against this reverse current, but that would affect the numbers for efficiency. Circuits using multiple power sources are rare, so I guess the efficiency is prioritized as a selling point.
Datasheets for complex devices are often tens or hundreds of pages long, even with omission of properties that are deemed unimportant.
I've read several threads on this forum mentioning failures of Nano Every boards. Analyzing the circumstances described, this 'reverse' diode is the most likely culprit. Simple measurement with a multimeter confirms its existence and the lack of any other safety mechanism. "If all other possibilities are rejected, the remaining one, however improbable, must be true."
Are there downsides to powering the servo and Arduino with the same external power supply? I've read that the servo might draw enough current from the battery to create issues for the battery's ability to power Arduino, but is this the case (especially when I only have one micro servo that is powered directly from the battery?) I'd ideally like to use only one battery (likely a 2 cell LiPo) in this circuit.
I see that sonofcy has mostly answered it, but what would the specific issue be with powering it with the same battery? Would this issue be present given that it's only one micro servo?
If the power supply can provide enough current for both the servo and the Nano Every, no.
So it's time for you to think how much time you want the setup to work, in order to decide how many mAh your LiPo pack needs to have.
My thoughts are now about your 2 cell LiPo being 7.4V. If you feed the Every through its VIN pin, the regulator can handle it, but you can't connect 7.4V directly into a servo that works on 4.8V. So you might need a separated regulator for the servo.
I saw the idea to use a 7805 regulator for the supply of the servo. These are rated 1A (with heat sink up to 1.5A). If the stall current of the servo is high, this regulator is not the solution. If it's lower than 1A use of the 5V output of the Nano Every is an option, and it even comes with the benefit of lower current drain from the battery. By the way: not only the voltage of your battery is important, but even more so the capacity (mAh).
I found a datasheet of a servo that is more or less comparable:
But this whole thread is about not using the Every to power the servo...
Post #5 states "in the neighborhood of 1A". Someone from Adafruit said 500mA.
If it was my project I would test the 7805.
PS: OP didn't mention how much weight the servo will be moving, or the torque needed, or how often it will be moving, which could help in the decision...
The general advice is not to use a board as a power source. Not because it is impossible but because it easy, and it is easy to damage the board if you don't regard the limitations. Still, having given that advice, they teach you power a servo from your board:
So, if you are careful about the limitations, things are possible (sometimes, and at your own risk).
Using a independent power source for the servo is the safe solution. It's just that if you need it, a 7805 might not be enough.
And even then, you should watch out. See post #6.
