Greetings,
Stupid question, but i need to know...
i have 12v DC adapter, as suggested to me by the arduino site.
Is it safe to plug it into the power input on my arduino Uno as an external power source? is there anything i need to keep in mind if supplying power this way rather than through the USB..
thanks,
cam
No should work fine, assuming it has sufficient current rating, 500ma to 1 amp is recommended. It is required that the center pin be the positive terminal, but as there is a polarity protection diode on board, no damage will result if you have a negative center pin plug, it just won't work. Just for your information if you have both the USB plugged in and the external power plugged in, the board takes power from the external power automatically.
Lefty
brillant, thanks for the reply lefty.
everything meets requirements, good to go..
also can you get a bad shock from an 12v 500ma power supply?
i know the basic safety precautions, i just don't know the risks.
thanks,
cam
also can you get a bad shock from an 12v 500ma power supply?
i know the basic safety precautions, i just don't know the risks.
Not unless you can physically contact the prongs that are plugged into the AC outlet. So no shock hazard, and if you short circuit the 12volt side most wall wart modules will just burn open an internal transformer winding and stop all current from ever passing again. 
And these are not stupid questions for someone that doesn't know. The stupid ones are the ones that don't know, know they don't know and then proceed without asking such questions. Or something like that.
Good luck
3 easy questions-
Is it a standard connection that I can get at Radio Shack?
I have a 12v, 1250 mA transformer with cut off ends. Is that too strong for the Uno? It's a fairly decent one, I've had it to max capacity with a 2.5A fan.
I guess the next logical question would be- what CAN and CAN'T you power it with?
Vlow-Vhigh and Alow-Ahigh I suppose, or maybe they do it in terms of Power. Easy conversion.
I have looked (briefly) for some documentation on it but I haven't found it. Unless it's packaged with the board, I should get that tomorrow.
Thanks- I'm so excited for this!!! ;D
Which arduino did you buy cam?
When I bought a duemilanove, it came with a 9V, 650mA wal-wart adapter. Or maybe I added it separately, was back in August & I don't recall anymore.
I now use that one for development & testing, and have moved on to using promini's embedded into projects, powered from 5V wallwarts
http://www.mpja.com/prodinfo.asp?number=18520+PS
that I connect directly to Vcc and bypass the onboard regulator.
or from 12v sources regulated down to 5V after going down a 30' cable (still needed 12v at the other end, but also needed 5v, so just powered the promini with that also, it turn transistors on that control strings of LEDs from 5v & 12v)
or 3.3V prominis running direct from a 1000mAH 3.7V LiPO battery in a remote control transmitter.
Is it a standard connection that I can get at Radio Shack?
Yes, I've bought them there, but usually avalible cheaper at other on-line parts vendors. RadioShack.com Official Site - America's Technology Store
I have a 12v, 1250 mA transformer with cut off ends. Is that too strong for the Uno? It's a fairly decent one, I've had it to max capacity with a 2.5A fan.
No matter how high the current rating of the transformer is the Arduino will draw only what it requires, so that will be fine as long as it's a DC voltage and not AC voltage output. You can wire it to the Arduino using either the external power connector, or directly to the sheild pins with the positive going to the Vin pin and negative to a ground pin.
I guess the next logical question would be- what CAN and CAN'T you power it with?
Can't power your kitchen oven with it nor your electric cloths dryer. Can power things that require +12vdc at 1.25 amps or less.
Also: anything that needs higher current draw, wire it in parallel with the arduino, don't try and take all your power thru the arduino 5v regulator.
Which arduino are you getting?