Arduino mini RAW input and solenoid circuit

Hi,

I'm new to the world of electronics and I'm hoping that someone on here can point me in the right direction with my first real project.

So what I want to do is to activate a 12V solenoid at a set time every day using an arduino pro mini (5V 16MHz) via the TimeAlarms lib.
I've got most of it figured out and working on a breadboard at this point but I have a question about hooking up the power supply.

I'm hoping to use a single regulated 12V DC(1A) power supply to power the whole thing.

I've got it set up so that the 12V supply feeds directly to one power rail on the breadboard and also connects to the RAW pin on the mini.
The 5V pin on the arduino then connects to the other power rail on the other side of the breadboard which provides 5V for the RTC module.

As the solenoid can generate unwanted voltage spikes due to induction I've included a snubber diode to protect the mosfet which I use for switching the solenoid circuit.

What I'm wondering about is if there is any danger to the power input on the arduino when the current is directed back through diode.

I know it has a regulator on board that steps voltages between 7v and 12v down to 5V but I'm wondering if this setup still presents any danger in overloading this regulator or if there are any extra precautions that I should be taking between the PSU and the arduino.

I'm including a link to my breadboard diagram here for reference.

http://s22.postimg.org/867g6r2n5/solenoid_circuit_bb.png

Any guidance or suggestions on what could be done better would be greatly appreciated.

Adding the free-wheel diode across the coil specifically stops your whole circuit being destroyed
by large voltages (not just the MOSFET). So long as the power supply can supply enough current for the
solenoid and the 12V is decoupled near the MOSFET you should be alright - assuming the supply is happy
with suddenly varying loads (that's partly why decoupling is used of course).

An extra precaution would be a TVS diode across the 12V supply to limit transient voltages (this
would back up if the diode failed and also protect from other sources of interference to the power).

Note that a 12V TVS diode won't limit your voltage to 12V, it will prevent it jumping by large amounts,
perhaps clamping by 16V or so - but that's enough to protect most 5V regulators used in Arduinos.

Thanks for the info, Mark. Its early days yet and I'm still figuring out a lot of the basic concepts so pointers like these are a great help. I'll defiantly do a bit of research into the TVS diode setup and see how it might apply here.