Is there a reason I shouldn’t use the Vin pin as a 5V source for projects when the core is being powered through the USB port?
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Some of the pins are 5V tolerant, but some are not. Please see Zach's post here for more info:
If you use the Vin pin for power, you may starve the Core of it's stable power supply if for instance you draw too much power with servos, high power LEDs or other heavy loads. This could cause the Core to brown out and reset. If that happens you could always try to use a beefier power source, such as a 5V 1A or 2A wall adapter, or separate battery power supply between 3.6V and 6V on Vin.
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So as long as the power requirements are carefully managed, it probably won’t cause issues?
It was more of an academic question, I have a USB cable from an old mouse that I can use as an independent USB power source. I remember reading that with Arduino, drawing current off a Vin pin could cause problems, so I was curious about the Spark Core.
You got it, anything could cause problems… but if you carefully manage it you’ll be fine!
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I am using the VIn successfully for a Relais-Shield that needs 5V… so far so good! But it only draws 40ma Max.
I had the same question, I wanted to try and use the VIN and GND from the Spark to power the BLE Mini but wasnt sure if that was a good idea. When i have the Spark plugged into the USB port on my laptop I am only showing 4.64v which made me think that if it wasnt putting the 5V out of the VIN on the Spark that maybe it couldnt handle the current. I just didnt want to fry the Spark so I thought I best check the forums first. Would it be better to power the BLE Mini (which I know is 5v) from the USB cable and have that go into the VIN on the Spark or am I just splitting hairs here? Any advice appreciated.
@contractorwolf, the Vin pin is connected to the USB voltage through a diode for protection. However, because of that diode, you will see a small voltage drop from Vusb (as you could see with 4.64V). That diode, from what I understand can handle about 500ma of current. All this to say that you can power the BLE Mini from Vin as long as it’s happy with the lower voltage. 
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@peekay123, thanks for the info, just didnt want to hurt the Spark, looks like I will be in the clear, thanks!
I know this is an old thread, but I am now trying something with the VIN pin that I wanted to see if it made sense. I am doing some LED Strips that use 12v and the power source I have has 12v with 5amps. Can I run that power supply into the VIN and power both the RGB LED strip and the sparkcore off that power supply or should I put a 5v regulator between the power supply and the VIN? Would that be too much power for the VIN? would it overheat the onboard regulator? Thanks!
@contractorwolf, you will need to add a 5V regulator. The Photon will only draw the current it needs so it won’t be “too much power”. However, stepping down from 12V, a typical LM7805 linear regulator will get quite warm. You could also use a DC-to-DC step-down regulator like this one from Pololu:
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@peekay123 thanks for the info and quick response. Should I get the 5v or the 6v and connect it to the VIN or should I get the 3.3v and go into the 3.3v pin on the sparkcore?
@contractorwolf, if you will not be using any 5v peripherals with your Photon then you can use the 3.3v one. Otherwise, use the 5v one. As long as it can supply 500ma or more.
@peekay123 I am using an old Sparkcore model, one of the second generation ones (black top) not the photon
@contractorwolf, oops! No matter, same rules apply 
Looking into the docs/datasheets does help
e.g. here
https://docs.particle.io/datasheets/core-datasheet/#power-regulator
Also keep in mind the Core is max 6V on VIN and Photon is max 5.5V on VIN. Thanks!
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Hello BDub, thanks for the info on MAX
I am using 5V to source a 5V device, and I do notice the metal chip(core) gets slightly warm to touch
Also my RX pin is not responding do you believe it could have been shorted out. D7 , A0 and A1 are NOT tolerant of 5V as per Zach comments posted above, What about RX and TX pins ? Are they 5V tolerant
Hi @Mapoint
This is a really old thread. It sounds like you are using the older Spark Core. The core datasheet is still available in the doc area here:
https://docs.particle.io/datasheets/discontinued-products/core-datasheet/
and it says:
The Spark Core offers a total 18 I/O pins to the user: D0 to D7, A0 to A7 and two pins that are preset to serial - TX and RX. All of these I/O pins run at 3.3V and the user should keep this in mind before attaching any external peripherals to them. The only exception to this are the following pins that are tolerant to 5V inputs:
D0, D1, D3, D4, D5, D6 and D7
Hi bko,
Thanks for the info, actually I am using Photon with current system version 0.7.0 And not spark core Thanks any updates on that ?
The datasheets for the Photon are most centainly in the documentation as well. Have you had a look at that yet?
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