Powersupply in car

This is most certainly a very stupid question:

  1. Can I power an Arduino UNO using the 12V in a car (that may go up to 14V depending on the charging state of the battery)

  2. If not - are there any "plug and play" solutions (12V in --> Arduino power out)

  3. If there is a similar black round power plug on an Arduino shield - can I assume that this shield can also be powered with the same voltage as the Arduino?

beejayf:
This is most certainly a very stupid question:

  1. Can I power an Arduino UNO using the 12V in a car (that may go up to 14V depending on the charging state of the battery)

Not advisable. 12V is the max spec, and that already gets pretty hot when you have stuff connected.

beejayf:
2) If not - are there any "plug and play" solutions (12V in --> Arduino power out)

Yes, a phone charger. Plug it into the USB port.
Alternatively, get something like an MP1584 module, set it to 7-8V and feed it into Vin.

beejayf:
3) If there is a similar black round power plug on an Arduino shield - can I assume that this shield can also be powered with the same voltage as the Arduino?

The "black round power plug" is specified up to higher voltages. If that thing was a shield that was supposed to do some 24V stuff, I would expect it to require 24V. So no, you cannot assume that.

Thanks a lot!

I'll give the 2.4A USB charger a try - hope that will be enough to power the sim900 GSM shield as well.

For lower currents, any of the cigarette lighter plugs with a usb output on them will work, however, only in the last post did you mention any current (2.4A?). If you are going to need that much current, you may need to purchase one of the many buck converters out there that are quite cheap. I would get one rated for at least 35-40 volts input (automotive circuits tend to have nasty spikes on them) and set for the output voltage you need - either 5v direct or 7-8 volts if you are using it as a pre-regulator before feeding it to the 5v regulator. You need to determine just what current you need and what voltage and then you can decide the best way to supply those needs.

The [u]specs[/u] say 7-12V recommended and 6-20V limit.

The "stress" on the voltage regulator is related to the voltage dropped across it and the current through it (and the ambient temperature). The more stuff your powering the more you have to be careful about the voltage. If you are just powering the Arduino, it should be safe up to 20V.

I've got an Arduino in a vehicle with the "12V" into the barrel jack, and I besides powering the Arduino itself, am driving a few regular LEDs.

  1. If there is a similar black round power plug on an Arduino shield - can I assume that this shield can also be powered with the same voltage as the Arduino?

Every shield is different. Check the specs. The good news is that if it has it's own power source it's not adding any load to the Arduino's voltage regulator.